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Year: 2019
A new fossil-Lagerstätte from the Late Devonian of Morocco : faunalcomposition, taphonomy and paleoecology
Frey, Linda
Posted at the Zurich Open Repository and Archive, University of ZurichZORA URL: https://doi.org/10.5167/uzh-177848DissertationPublished Version
Originally published at:Frey, Linda. A new fossil-Lagerstätte from the Late Devonian of Morocco : faunal composition, taphon-omy and paleoecology. 2019, University of Zurich, Faculty of Science.
A New Fossil-Lagerstätte from the Late Devonian of Morocco: Faunal
Composition, Taphonomy and Palaeoecology Dissertation
zur
Erlangung der naturwissenschaftlichen Doktorwürde (Dr. sc. nat.)
vorgelegt der
Mathematisch-naturwissenschaftlichen Fakultät
der
Universität Zürich
von Linda Frey
von
St. Ursen FR
Promotionskommission
Prof. Dr. Christian Klug (Leitung der Dissertation) Prof. Dr. Hugo Bucher Prof. Dr. Marcelo Sánchez
Prof. Dr. Michael Coates
Dr. Martin Rücklin
Zürich, 2019
ABSTRACT ................................................................................................................................................2
INTRODUCTION......................................................................................................................................5
CHAPTER I Late Devonian and Early Carboniferous alpha diversity, ecospace occupation,
vertebrate assemblages and bio-events of southeastern Morocco ..............................27
CHAPTER II Fossil-Lagerstätten and preservation of invertebrates and vertebrates from the
Devonian in the eastern Anti-Atlas (Morocco) ...........................................................61
CHAPTER III Morphology, phylogenetic relationships and ecomorphology of the early
elasmobranch Phoebodus ............................................................................................89
CHAPTER IV Functional morphology of mandibular arches in symmoriids as exemplifi ed
by Ferromirum oukherbouchi gen. et sp. nov. (Late Devonian) ...............................135
CONCLUSIONS ....................................................................................................................................167
APPENDIX
Appendix A Collaboration with other projects (abstracts) ............................................................171
Appendix B Additional article published during doctoral studies ................................................175
ACKNOWLEDGEMENTS ..................................................................................................................203
CURRICULUM VITAE ........................................................................................................................207
2
Abstract
The Late Devonian (382. 7 to 358.9 Ma) was a period of intense environmental perturbations and fun-damental changes in marine ecosystems impacting also the marine vertebrates. Two extinction events, namely the Kellwasser Event (Frasnian-Famennian boundary) and the Hangenberg Crisis (latest Devoni-an) caused severe losses in diversity. Especially several groups of gnathostomes were strongly affected by the Hangenberg Crisis, which represents a bottleneck in the evolutionary history of jawed vertebrates. The marine ecosystem became reshaped and the previously diverse placoderms went extinct and the taxonomic diversity of acanthodians decreased, while other chondrichthyans and osteichthyans diversifi ed. From the stratigraphic interval between the Kellwasser and the Hangenberg crises, well-preserved remains of plac-oderms and isolated teeth were well documented from Morocco before. By contrast, articulated remains of chondrichthyans were discovered only recently from the Famennian of the Maïder region (Morocco) within this PhD project. Most fossil fi sh were found in a stratigraphic interval with abundant remains of thylacocephalan arthropods preserved in ferruginous nodules (early/ middle Famennian Thylacocephalan Layer). These gnathostomes include both known and new taxa of sarcopterygians (onychodontids), plac-oderms (Dunkleosteus, Titanichthys, Alienacanthus and Driscollaspis) and chondrichthyans (phoebodon-tids, symmoriids, and several new cladodont chondrichthyans). In the framework of this thesis, the remains of chondrichthyans were in the main focus because their skeletons are rarely preserved in the fossil record due to the fragility of their cartilaginous skeletons. The Famennian chondrichthyans of the Maïder region often preserve three-dimensional skulls, the visceral as well as postcranial skeleton (pectoral and pelvic girdles with articulated fi ns, dorsal fi ns with fi n spines, neural arches and sometimes the caudal fi n) and even mineralized soft-tissues (muscles, liver, digestive tract). Therefore, the discovery of such remains of Devonian chondrichthyans is of importance to examine their phylogenetic relationships, their morpholog-ical disparity and to reconstruct their ecological diversity including changes in the respective ecological roles of these vertebrate groups in the marine ecosystems.
In chapter I, the palaeoenvironment of the gnathostome-bearing stratigraphic interval of the Maïder was quantitatively investigated by analysing the diversity and palaeocology of the accompanying inverte-brate faunas. For this purpose, 21 invertebrate associations from early Famennian to early Carboniferous age of the Maïder region (17 from Madene el Mrakib, four from Aguelmous) were sampled and deter-mined. Based on the composition of these associations, alpha diversity (changes in species richness at a single locality through time), ecospace occupation (three-dimensional modes of life including tiering, motility, and feeding mode) and trophic nucleus (dominant taxa of each association) were analysed. The species richness, ecospace occupation as well as the ratio between pelagic and benthic organisms were fl uctuating during the Famennian and Tournaisian. Those ecological changes correlate with numerous bio-events coinciding with fl uctuating global and/ or regional sea level and changes in oxygenation during the Devonian. Although the sea fl oor might have been a bit better oxygenated (extended ecospace includ-ing benthic modes of life) in some stratigraphic intervals, the Fammennian of the study area was mostly hypoxic to dysoxic because of the low taxonomic diversity of benthic invertebrates and the dominance of pelagic or benthic taxa tolerant to oxygen depletion. This is supported by the absence of benthic gnatho-stomes in the Maïder (including microremains).
The taphonomy of the gnathostomes of the Famennian Thylacocephalan Layer and some other Devo-nian Fossillagerstätten was investigated in Chapter II. The mineral composition of the remains of gnatho-stomes, thylacocephalans and some other invertebrates from various localities were analysed by Raman spectroscopy and X-ray diffraction. To understand the genesis of the Famennian Fossillagerstätten, the mineral analyses were combined with the current knowledge of the palaeogeography and palaecology of the Maïder region. The fossils mainly contain iron oxides (oxidised pyrite) and phosphates. The Maïder was a basin isolated by land and two submarine ridges (Tafi lalt and Maïder Platform) from neighbouring basins, which limited water exchange and thus also oxygen supply during the Devonian. This palaeogeo-graphic setting in combination with the mineral composition of the fossils, the soft-tissue preservation and the low abundance of benthos (even a complete lack of benthic chondrichthyans), the Thylacocephalan Layer with exceptionally well-preserved chondrichthyans represents the fi rst Konservat-Lagerstätte (con-servation deposit) of the Devonian of North Africa.
In chapter III, the morphology and palaeoecology of Phoebodus, a common and cosmopolitan chon-drichthyan from the Devonian (Givetian to Famennian), previously only known from isolated teeth, is
3
Abstract
described. Phoebodus saidselachus sp. nov. of the Famennian of the Maïder region is the fi rst specimen of this genus preserving body, soft-tissue and skull remains. Its body and skull are slender and more elongate than those of other Palaeozoic chondrichthyans. Phylogenetic analyses based on a data matrix including 228 characters of 65 taxa and one outgroup taxon place Phoebodus saidselachus sp. nov. within the stem elasmobranchs. Therefore, the Devonian genus Phoebodus is the oldest stem elasmobranch with an elon-gate body shape. Other stem elasmobranchs with such body shapes are known from younger strata such as the phoebodontid Thrinacodus gracia from the Carboniferous of Bear Gulch and several taxa of xenacan-thids from the Permian. Therefore, chondrichthyans were morphologically and ecologically more diverse in the Devonian before the vertebrate bottleneck of the Hangenberg Crisis than previously thought.
Chapter IV focuses on the jaw function of symmoriiform chondrichthyans. Although the fossil re-cord of Palaeozoic chondrichthyans improved in recent years, the functional morphology of anatomical elements such as the visceral skeleton are not known in detail due to the often fragmentary or deformed preservation. For example, there was a long debate about whether hyoids had a suspensory function or not (aphetohyoidean hypothesis) in symmoriids. The newly discovered chondrichthyan Ferromirum oukher-bouchi gen. et sp. nov. from the Maïder Basin has exceptionally well-preserved and undeformed mandib-ular and branchial arches. The remains of the specimen were three-dimensionally reconstructed on the basis of CT-scans using the 3D reconstruction software Mimics. 3D-prints of the virtually reconstructed specimen allowed to mechanically examine the function of the mandibular and branchial arches. Due to the arrangement of the hyoids and jaws, it can be confi rmed that the hyoids had a suspensory function (aphetohyoidean hypothesis falsifi ed). Moreover, because of the confi guration of the jaw-articulation, the lower jaws performed a lateral and outward rotation when the chondrichthyan opened its mouth. As a result of this movement, the predatory success was probably improved since a greater portion of the dentition becomes functional than previously thought. This kind of jaw function is not known from recent chon-drichthyans and possibly vanished with the extinction of the symmoriids.
As general conclusion, the Famennian Konservat-Lagerstätten of the Maïder Basin bear abundant remains of various early gnathostomes and thylacocephalans. These gnathostomes were fossilized under oxygen depleted conditions on the sea fl oor of the Maïder Basin as corroborated by 1) the preservation in ferruginous nodules, 2) by the low diversity of accompanying benthic invertebrate, 3) by the domi-nance of taxa living in the water column (both invertebrates and vertebrates) and 4) the co-occurrence of benthic taxa tolerant to anoxic to dysoxic conditions. The two newly described taxa of chondrichthyans (Phoebodus saidselachus sp. nov and Ferromirum oukherbouchi gen. et sp. nov.) yielded new data on the morphology, phylogeny, diversity and functional morphology of Devonian chondrichthyans. Considering that much more taxa of early gnathostomes were discovered than presented here, the Famennian Konser-vat-Lagerstätten of the Maïder are of great importance to further study disparity and diversity trends of these early vertebrates as well as their ecology and evolution in the future.
INTRODUCTION
7
Introduction
Devonian Period: an overview
The Devonian (~419 to 259 Ma years) is the third
period of the Palaeozoic. It is subdivided into four
epochs and seven stages: the Early (Lochkovian,
Pragian, Emsian), Middle (Eifelian, Givetian) and
Late (Frasnian, Famennian) Devonian (Cohen et
al. 2013, updated 2018). At this time, two main
continents persisted: the larger continent Gond-
wana south of the equator and Euamerica (also
known as Laurussia), which was situated north-
east of Gondwana (Scotese 2001; Fig. 1A). The
two continents were separated from each other by
the Palaeotethys and the Variscan Sea (Neugebau-
er 1988). The climate throughout the Devonian
was generally warm to tropical (30°C) interrupted
by a somewhat cooler period (23 to 25°C) during
the Middle Devonian (Joachimski et al. 2009; Fig.
1B). Towards the end of the Devonian, the climate
cooled down for a second time (Joachimski &
Buggisch 2002).
Among others, the Devonian period is famous
for the rise of land plants, in particular the evolu-
tion of vascular plants, and the establishment of
the fi rst forest ecosystems (Rettalack 1997; Algeo
and Scheckler 1998; Stein et al. 2012). In the ma-
rine realm, the fi rst ammonoids with coiled shells
evolved from the straight-shelled to slightly coiled
bactritoids during the Early Devonian (Korn &
Klug 2002). In the context of my thesis, howev-
er, it is the great evolutionary success of jawed
fi shes in that time. Accordingly, the Devonian
is also called the “Age of Fish” because various
groups of jawed fi sh (gnathostomes) radiated and
established in the early marine and freshwater en-
vironments (Fig. 2A). Several of the main groups
of gnathostomes survived until today such as sar-
copterygians (lobe-fi nned fi sh), actinopterygians
(ray-fi nned fi sh), and chondrichthyans (cartilagi-
nous fi sh). By contrast, two important Devonian
groups of gnathostomes such as the placoderms
and ‘acanthodians’ (a probably paraphyletic
group of cartilaginous fi sh) vanished throughout
Earth`s history (Fig. 2B). The placoderms had a
characteristic bony armor consisting of thick der-
mal plates in the head and thorax region while
their tail was naked or covered by scales and they
were roaming the waters for around ~120 Ma
years (Silurian to Devonian; Long & Trinajstic
2010). ‘Acanthodians’ persisted longer (Silurian
to Permian) than the placoderms and they include
small chondrichthyans exhibiting usually several
pairs of fi ns that usually carry spines, hence the
name (Hanke et al. 2001; Karatajute-Talimaa &
Smith 2002; Burrow 2003, Denison 1979). Their
phylogenetic relationships within the group and
to other fi sh groups are still not clarifi ed due to
their fossil record of often complete but heavily
fl attened fossils (Blais 2017). Most phylogenetic
studies revealed them as a paraphyletic group of
stem chondrichthyans (Brazeau 2009; Davis et al.
2012; Zhu et al. 2013; Giles et al. 2015; Long et
al. 2015; Burrow et al. 2016; Coates et al. 2017)
but some taxa might also represent stem osteich-
thyans (Brazeau 2009, Davis et al. 2012).
A fundamental step in evolution, namely the
transition from fi sh to tetrapod (four-limbed ver-
tebrates) and thus from aquatic to terrestrial life
took place during the Devonian. Fossil bodies
of tetrapods and closely related tetrapodomorph
fi shes are known from the Middle and Late De-
vonian (e.g., Campbell & Bell 1977; Ahlberg
1998; Ahlberg & Clack 2006; Ahlberg et al. 1994,
2005, 2008; Lebedev & Clack 1993; Lebedev &
Coates 1995; Zhu et al. 2002; Shubin et al. 2004;
Daeschler et al. 2006). Tetrapodomorph fi shes
such as the elpistostegalians are sarcopterygians
already exhibiting tetrapod-like characters in their
fi ns (e.g., Panderichthys in Boisvert et al. 2008;
Clack 2012). This fact in combination with the
mostly aquatic lifestyle of Devonian tetrapods in-
cluding the famous Acanthostega and Ichthyoste-
ga evidence the initial evolution of limbs from
fi ns in aquatic environments (Coates 1996; Coates
& Clack 1995; Coates & Ruta 2007; Clack 2012).
8
Introduction
As mentioned above, the Devonian was a pe-
riod of early animal and plant radiation and of
evolutionary key events such as the fi sh-tetrapod
transition. However, the Devonian ecosystem
also faced several extinction events (Walliser
1996; House 2002; Fig. 3). The most fundamental
changes in this early ecosystem occurred at the
latest Frasnian (Kellwasser Crisis; e.g., McGhee
1988; Buggisch 1991; McGhee 2001; Sandberg
et al. 2002; Gereke & Schindler 2012) and at the
end-Famennian (Hangenberg Crisis; e.g., Caplan
& Bustin 1999; Kaiser et al. 2006, 2008, 2015;
Carmichael et al. 2015; Becker et al. 2016). The
Kellwasser event strongly affected the marine
Figure 1. Palaeogeography and temperature curve of the Devonian. A. Palaeomap shows continents and
oceans of the Late Devonian (370 Ma years), modifi ed map from Deep Time Maps (Blakey 2016, https: //
deeptimemaps.com). B. Temperature curve of the surface waters, adopted from Joachimski et al. (2009).
9
Introduction
biodiversity, which is evident by the loss of about
72-80 % of all species (McGhee 2014). The Han-
genberg Crisis is also regarded as a bottleneck
in vertebrate evolution as many habitats of ear-
ly vertebrates underwent fundamental changes:
while sarcopterygians suffered a severe loss in di-
versity and the placoderms got extinct, chondrich-
thyans and actinopterygians diversifi ed rapidly af-
ter the crisis (Sallan & Coates 2010). Causes for
the changes in the environment and biodiversity
during the Late Devonian are still under debate.
Some possible causes are marine anoxia (Caplan
Figure 2. Devonian groups of gnathostomes. A. Biodiversity through time, source: Benton (2005). B.
Reconstructions of some early gnathostomes: 1. Bothriolepis, 2. Remigolepis, 3. Groenlandaspis, 4. Ho-
loptychius, 5. Moythomasia, 6. Culmacanthus, 7. Akmonistion. Reconstructions are taken from Sampson
(1956); Jessen (1968); Lauder & Liem (1983); Young (1989a, b, 2007); Long (1983, 1991); Cloutier &
Schultze (1996); Coates & Sequeira (2001); Choo (2015).
10
Introduction
& Bustin 1999; Riquier et al. 2006), sea level fl uc-
tuations (Kaiser et al. 2006), global cooling (Joa-
chimski & Buggisch 2002), eutrophication (Al-
geo & Scheckler 1998; Algeo et al. 1995, 2001)
and decreased marine selenium level (Long et al.
2015).
Devonian of Morocco
Morocco can be regarded as a window into
Earth`s deep history because its outcrops yield
many geological, sedimentological and palaeon-
tological information about past ecosystems from
the Proterozoic to today. During the Devonian
period, Morocco was situated at the northwestern
margin of Gondwana and a lot of its surface was
covered by an epicontinental sea (Scotese 2002;
Dopieralska 2009). Exposed Devonian sediments
cover a large area of about 20000 km2, which
often bear highly fossiliferous strata (Kaufmann
1998). Some of the most famous regions for De-
vonian fossils are the Tafi lalt and the Maïder in
the eastern Anti-Atlas. In these regions, two ma-
rine basins (Tafi lalt and Maïder Basin) formed in
the Palaeozoic, which were connected via the Ta-
fi lalt platform with shallower water (Wendt 1985,
1995; Wendt et al. 2006; Fröhlich 2004; Lubeseder
et al. 2010; Fig. 4). From this region, many fossil
groups of marine animals have been documented.
Particularly invertebrates are extremely abundant
such as trilobites (e.g., Struve 1990; Klug et al.
2009; Chatterton and Gibb 2010), crinoids (e.g.,
Klug et al. 2003; Webster et al. 2005; Berkows-
ki & Klug 2012), brachiopods (e.g., Franchi et al.
2012; Halamski & Baliński 2013; Tessitore et al.
2013; Sartenaer 1998, 1999, 2000), bivalves (e.g.,
Kříž 2000; Hryniewicz et al. 2017), and cepha-
lopods including ammonoids (e.g., Korn 1999;
Klug 2002; Klug et al. 2008; Klug et al. 2016;
Becker 2002; Kröger 2008; De Baets et al. 2010,
2012; Korn & Bockwinkel 2017; Korn et al. 2014,
2015a, b, 2016a,b). Due to the high abundance
and/ or exceptional preservation of macrofos-
sils, several localities could be actually regarded
as Fossillagerstätte (Frey et al. submitted, Chap-
ter II). As far as vertebrates are concerned, their
peak abundance is in the Late Devonian strata of
the eastern Anti-Atlas. Previously, the record of
articulated remains of Devonian vertebrates was
limited to more or less complete body and skull
parts of placoderms and sarcopterygians (Leh-
Figure 3. The big fi ve mass-extinctions after Sepkoski (2002) are marked by red lines. During the Devoni-
an, two major crises (Kellwasser and Hangenberg) shaped the early vertebrate biodiversity. Figure adopted
from Friedman & Sallan (2012).
11
Introduction
mann 1956, 1964, 1976, 1977, 1978; Lelièvre &
Janvier 1986, 1988; Lelièvre et al. 1993; Rücklin
2010, 2011; Rücklin et al. 2015; Rücklin & Clé-
ment 2017; Fig. 5 A-D, J). By contrast, actinopte-
rygians and chondrichthyans are rare and only fi n
spines, teeth, scales and few remains of isolated
jaws were published (Termier 1936; Lehman
1976; Derycke 1992; Hampe et al. 2004; Dery-
cke et al. 2008, 2014; Ginter et al. 2002; Klug
et al. 2016; Derycke 2017; Fig. 5E-I). Recently,
new material of Famennian (Late Devonian) plac-
oderms, sarcopterygians, actinopterygians and
chondrichthyans were found in the Maïder Basin
(Frey et al. 2018, Chapter I, Fig. 6 A-D). In par-
ticular, the chondrichthyans are well-preserved
with sometimes three-dimensional skulls as well
as more or less complete and articulated bodies.
In this PhD project, I focused on these early chon-
drichthyans because they bear a plethora of new
anatomical, ecological and phylogenetic informa-
tion about this group (Chapter III and IV).
Global mass extinction events such as the Kell-
wasser Crisis (latest Frasnian; Wendt and Belka
1991) and the Hangenberg Crisis (end-Devoni-
an; e.g. Korn et al. 2004; Kaiser et al. 2011) are
recognizable along with some smaller bio-events
in the Late Devonian of Morocco (House 1985;
Becker 1993; Hartenfels & Becker 2009, 2016a,
b). These events often coincided with dysaerobic
or anoxic conditions and/ or transgressions on a
regional scale (Wendt and Belka 1991; Kaiser et
al. 2015; Hartenfels 2011). The new material of
gnathostomes from the Maïder comes from this
environmentally unstable interval between the
Kellwasser and Hangenberg crises. For this rea-
son, I also investigated changes in environmental
conditions, which affected the early gnathostomes
faced in this marine basin in detail (Frey et al.
2018; Chapter I).
Palaeozoic chondrichthyans
Devonian chondrichthyans are characterized by
a skeleton consisting of calcifi ed tessellated car-
tilage, multiple rows of teeth that are replaced
throughout life and by a body often covered by
placoid scales. Extant chondrichthyans include
the subclasses Elasmobranchii (sharks and rays;
around 1100 species) and Holocephali (chimaeras;
Figure 4. Topography and bathymetry of the Maïder and Tafi lalt area in the southeastern Anti-Atlas
during the Late Devonian. Figure is adopted from Dopieralska (2009).
12
Introduction
around 50 species; Compagno et al. 2005). Some
of the oldest known putative remains of chon-
drichthyans are scales from the Llandovery (Silu-
rian) of Central Asia: e.g., Mongolepis, Teslepis,
Sodolepis, Udalepis, Xinjiangichthys, Shiqianole-
pis, Elegestolepis and Tuvalepis (Karatajūtė-Tali-
maa 1973, 1995; Karatajūtė-Talimaa et al. 1990;
Karatajūtė-Talimaa & Novitskaya 1992; Novits-
kaya & Karatajūtė-Talimaa 1986; Zhu 1998; San-
som et al. 2000; Žigaitė & Karatajūtė-Talimaa
2008). Probably even older chondrichthyan scales
from the Ordovician were reported such as Tan-
talepis and Areyongalepis (Sansom et al. 1996,
2012; Young 1997, 2000; Fig. 7A).
The oldest remains that are more widely ac-
cepted as remains of chondrichthyans are the teeth
of Leonodus from the Early Devonian (Mader
1986, Fig. 7B). First skeletons of stem chondrich-
thyans were documented from the Early/Middle
Devonian; these fi nds comprise braincases with
parts of the visceral skeleton of Doliodus (Miller
et al. 2003; Maisey et al. 2009, 2017; Fig. 8A, B),
Pucapampella (Janvier & Suárez-Riglos, 1986,
Maisey & Anderson 2001), Gladbachus (Heidtke
& Krätschmer 2001; Coates et al. 2018; Fig. 8C,
D) and Anarctilamna (Young 1982).
From the Famennian (Late Devonian) on-
wards, remains of chondrichthyans become more
abundant although many discoveries mainly in-
clude isolated fi n spines (e.g., ctenacanthids;
Figure 5. Remains of Late Devonian gnathostomes from Morocco. A-D. Skull plates of the placoderm
Driscollaspis pankowskiorum Rücklin et al., 2015, dorsal (A-B) and lateral (C-D) views, scale bar = 5
cm. E-F. Teeth of Phoebodus gothicus Ginter, 1990, scale bar = 0.5 mm. G. Symphyseal tooth-whorl of
an acanthodian, scale bar = 0.5 mm. H-I. Teeth of actinopterygians, scale bar = 100 μm. J. Teeth and jaw
remains of onychodontid sarcopterygian. Sources of fi gures: A-D.: Rücklin et al. (2015); E-G.: Ginter et
al. (2002); H-I.: Derycke et al. (2008); J: Lehmann (1976).
13
Introduction
Maisey 1981, 1982a, 1984a) and teeth of, e.g.,
Omalodontiformes Turner, 1997, Protacrodon-
toidea Zangerl, 1981 and Orodontiformes Zangerl,
1981 (Ginter et al. 2010). One of the most famous
and best documented Famennian chondrichthyan
known from complete and articulated skeletons is
Cladoselache Dean, 1894A from the Cleveland
Shales of Ohio, USA. Cladoselache has a shark-
like morphology including a torpedo-shaped
body with a crescent outlined caudal fi n, paired
pectoral and pelvic fi ns, two dorsal fi ns with fi n
spines and teeth arranged in several tooth fi les
(e.g. Dean 1894A, 1909; Bendix-Almgreen 1975;
Harris 1938a, b; Maisey 1989b, 2007; Schaeffer
1981; Williams 2001; Woodward & White 1938).
These early chondrichthyans were assigned to
elasmobranchs for a long time but recent stud-
ies provided evidence that Cladoselache is more
closely related to holocephalans (Coates et al.
2017; Fig. 9A, 9E). Coates et al. (2017) assigned
another common and divers Palaeozoic group of
chondrichthyans, namely the Symmoriiformes
Figure 6. Late Devonian localities in the Maïder region bearing remains of gnathostomes. A. Madene el
Mrakib, B. Bid er Ras, C. Shivering layer contains nodules with thylacocephalan arthropods and gnatho-
stomes, D. Fin remains of a chondrichthyan in the fi eld.
14
Introduction
Zangerl, 1981, to the holocephalans. Symmoriid
chondrichthyans persisted from the Devonian to
the Permian and exhibit symplesiomorphies such
as a whip-like structure connected to the metapte-
rygium of both pectoral fi ns, a reduced fi rst dorsal
fi n and reduced or specialized dorsal fi n spines
(e.g. Zangerl 1981; Lund 1985, 1986; Coates &
Sequeira 2001). In Cobelodus Cope, 1893, Sym-
morium and Denaea Zangerl, 1981, the anterior
of the two dorsal fi ns and the dorsal fi n spines are
absent while Falcatus, Damocles, Stethacanthus
and Akmonistion exhibit a derived structure at the
position of the anterodorsal fi n (Zangerl 1981,
1984, 1990; Zangerl & Case 1986; Williams 1985;
Fig. 9F-H). A so-called spine-brush complex is
present in Stethacanthus and Akmonistion, which
consists of an anterior spine and posteriorly of a
brush out of globular calcifi ed cartilage covered
by large spiny scales (Coates et al. 1998; Coates
& Sequeira 2001). Instead of this spine-brush
complex, Falcatus and Damocles dorsally have a
hook-like appendage (Lund 1985, 1986). Because
such structures are absent in modern chondrich-
thyans, their function is not yet known. The spine-
brush complex may speculatively have served
to scare off predators due to the resemblance of
this complex to a large, opened mouth (Zangerl,
1984). This interpretation appears doubtful be-
cause the spine-brush complex and the hooks are
only found in male specimens and it appears more
plausible that they played a role in mating (Lund
1985; Coates et al. 1998). The affi nity of sym-
moriids to holocephalans is further supported by
anatomical details seen in a three-dimensionally
preserved braincase of Dwykaselachus oosthui-
zeni Oelofsen 1986 by Coates et al. (2017): this
specimen shows chimaeroid-like character states
such as, for example, an elevated midbrain cham-
ber, large orbits and a similarly arranged otic lab-
yrinth (Coates et al. 2017). In the Famennian of
Morocco, we discovered well-preserved remains
of two new taxa of symmoriids that give new in-
sights into the ecology of the entire group (Frey et
al. in prep., Chapter IV) .
Another group of holocephalans that get some
attention are the Eugeneodontiformes that were
abundant during the Permian and Triassic (Zan-
gerl 1981). Their tooth whorls are planispirally ar-
ranged forming sometimes a saw-blade like denti-
tion such as in Edestus and Helicoprion (Ginter et
al. 2010; Fig. 10). Both taxa might have used the
tooth whorls for slashing medium-sized to large
prey (Itano 2014, 2015, 2018). Generally, holo-
cephalans were taxonomically and ecologically
more divers during the Palaeozoic than today and
many different groups have been documented
Figure 7. Putative scales and teeth of earliest
chondrichthyans. A. Scales of Tantalepis gate-
housei Sansom et al., 2012 from the Ordovician,
scale bar = 50 μm. B. Teeth of Leonodus carlsi
Mader, 1986 from the early Devonian, scale bar =
0.5 mm. Source of picture: Sansom et al. (2012)
and Ginter et al. (2010).
15
Introduction
from the Carboniferous of the Bear Gulch Lime-
stone in Montana, USA (Lund & Grogan 1997;
Lund et al. 2012, 2015).
Compared to holocephalans, fewer groups of
Palaeozoic elasmobranchs were discovered so far.
Among those, representatives of the phoebodon-
tids, xenacanthids, hybodontids and ctenacanthids
are locally quite common and thus the best docu-
mented. Previously, phoebodontids, a nearly cos-
mopolitan group, were known by a great number
of isolated teeth and by articulated skeletons of a
single species, namely Thrinacodus gracia (Gro-
gan and Lund, 2007) (Ginter et al. 2010; Fig. 11).
Figure 8. Stem chondrichthyans of Early and Middle Devonian age. A-B. Fossil remains and illustration
of Doliodus problematicus Miller et al., 2003, scale bar = 1 cm. C-D. Threedimensional reconstruction
of Gladbachus adentatus Heidtke and Krätschmer, 2001 based on computer tomographs, scale bar = 5
cm. Abbreviations: bhy, basihyal; bbra; anterior basibranchial; bbrp, posterior basibranchial; cbr, cerato-
branchials (I-V?); chy, ceratohyal; hb, hypobranchial; mc, Meckel’s cartilage; mmd, location of mucous
membrane denticles on counterpart; na, neural arches; nc, neurocranium; or, orbital ring; pop, postorbital
process; pq, palatoquadrate; pfs, pectoral fi n-spines; rad, radials; sco, scapulocoracoid; sp, partial spines;
sym, symphysis; tth, area with in situ teeth; thf, in situ tooth family. Figures adopted from Miller et al.
(2003) and Coates et al. (2018).
16
Introduction
However, the very common genus Phoebodus was
solely known by their widespread characteristic
tricuspid teeth and isolated putative fi n spines in
spite of its rather cosmopolitan distribution during
the Middle and Late Devonian (Ginter et al. 2002;
2010). Recently, we found the fi rst remains of ar-
ticulated skulls and postcrania of Phoebodus in
the Famennian of the Maïder region in Morocco
(Frey et al. in prep., Chapter III).
Xenacanthids are rather closely related to
phoebodontids and their remains have been doc-
umented from Late Devonian to Triassic occur-
rences (Ginter et al. 2010, Frey et al. in prep.,
Figure 9. Phylogeny and some representatives of early chondrichthyans. A. phylogenetic relationships
of early and some extant chondrichthyans adopted from Coates et al. (2018), red: stem chondrichthyans,
blue: elasmobranchs, yellow; holocephalans. B. Onychoselache traquairi (Dick, 1978), C. Squalus sp.,
D. Triodus sessilis, E. Cladoselache Dean, 1894A, F. Akmonistion zangerli Coates and Sequeira, 2001,
G. Cobeldodus Cope, 1893 H. Falcatus falcatus Lund, 1985. Reconstructions: B. Coates & Gess (2007);
C-D. Schaeffer & Williams (1977); E. Schaeffer (1967); F. Coates & Sequeira (2001); G. Zangerl and Case
(1976); H. Lund (1985).
17
Introduction
Chapter III). They had an elongated body with a
dorsal fi n extending along the entire body length,
a dorsal cranial spine and diplodont teeth (crown
with two long lateral cusps and a reduced medi-
an cusp; Dick 1981; Heidtke 1982, 1999; Hot-
ton 1952; Schaeffer 1981; Solér-Gijon & Hampe
1998; Hampe 2003; Heidtke et al. 2004; Fig. 9D).
A group of early chondrichthyans that is phy-
logenetically most closely related to the Neosela-
chii (modern sharks and rays) are the hybodonts
(Maisey 1984b; Maisey et al. 2004; Coates &
Gess 2007; Fig. 9A). The hybodonts are a group
that persisted from the Devonian to the Creta-
ceous (Mesozoic). They show derived conditions
in many parts of their skeleton compared to oth-
er early elasmobranchs. In addition to many dif-
ferences in the braincase, their shoulder girdle is
similar to that of extant elasmobranchs (Fig. 9B);
the pectoral fi ns have a tribasal arrangement (bas-
al elements are separated into propterygium, me-
sopterygium and metapterygium); a puboischiad-
Figure 10. Helicoprion bessonowi Karpinsky, 1899A, tooth spiral, scale bar = 5 cm. Source of picture:
Ginter et al. (2010).
Figure 11. The phoebodontid Thrinacodus gracia (Grogan & Lund, 2008) from the Carboniferous of Bear
Gulch, Montana. Scale bar = 5 cm. Picture taken from Grogan & Lund (2008).
18
Introduction
ic bar (left and right halves of the pelvic girdle
are fused) is present; the palatoquadrate is not the
cleaver-shaped (instead they have a lateral quad-
rate fl ange); and labial cartilages are present (e.g.
Dick 1978; Dick & Maisey 1980; Maisey 1982b,
1983, 1987, 1989; Maisey and de Carvalho 1997;
Coates & Gess 2007; Lane 2010; Lane & Maisey
2009, 2012; Coates & Tietjen 2018).
In this thesis, I focus on two groups of chon-
drichthyans, namely the phoebodontids and sym-
moriids. The recently discovered material of these
two groups of the Devonian of Morocco yields
important information about the phylogenetic
relationships and ecomorphological disparity of
some of the earliest chondrichthyans.
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CHAPTER I
Late Devonian and Early Carboniferous alpha diversity,
ecospace occupation, vertebrate assemblages and bio-events
of southeastern Morocco
Linda Frey, Martin Rücklin, Dieter Korn and Christian Klug
Published in:
Palaeogeography, Palaeoclimatology, Palaeoecology, 496 (2018), 1-17
https://doi.org/10.1016/j.palaeo.2017.12.028
29
Chapter I: Alpha Diversity and Palaeoecology
Contents lists available at ScienceDirect
Palaeogeography, Palaeoclimatology, Palaeoecology
journal homepage: www.elsevier.com/locate/palaeo
Late Devonian and Early Carboniferous alpha diversity, ecospace
occupation, vertebrate assemblages and bio-events of southeastern Morocco
Linda Freya,⁎
, Martin Rücklinb, Dieter Kornc, Christian Kluga
a Palaeontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, CH-8006 Zurich, SwitzerlandbNaturalis Biodiversity Center, Postbus 9517, 2300, RA, Leiden, The NetherlandscMuseum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, D-10115 Berlin, Germany
A R T I C L E I N F O
Keywords:
Fossillagerstätte
Famennian
Gnathostomes
Invertebrates
Palaeoecology
Sea level
A B S T R A C T
The Late Devonian was a time of dramatic environmental perturbations affecting marine ecosystems. Both the
Kellwasser (latest Frasnian) and the Hangenberg crises (latest Famennian) are primarily reported as phases of
drastic decreases in marine diversity while the Hangenberg Crisis is also described as a bottleneck in vertebrate
evolution. Fossil-bearing localities with Upper Devonian strata are of great interest to assess variations in the
effects of environmental perturbations on biodiversity. For this purpose, we examined changes in alpha diversity
and ecospace utilization of 21 Famennian (Late Devonian) and early Tournaisian (Early Carboniferous) in-
vertebrate associations containing 9828 specimens from Madène el Mrakib and Aguelmous (southern Maïder
Basin, northeastern Anti-Atlas, Morocco), where some layers yield exceptionally preserved gnathostome re-
mains. Both the invertebrate and vertebrate associations contain predominantly opportunistic and pelagic taxa
indicating oxygen depletion near the seafloor in this region. Nevertheless, the ecospace extension was fluctuating
and correlated with regional and/or global sea-level changes and oxygenation of bottom waters. In the Maïder
Basin, the ecospace was depleted after and during several bio-events such as the Kellwasser and Hangenberg
crises, the Annulata event (middle Famennian) as well as during the early Tournaisian. Abiotic as well as biotic
changes (instability of the invertebrate ecosystem) are considered to have influenced Famennian vertebrate
diversity because they were more or less directly dependent on invertebrates as a food source.
1. Introduction
Fundamental environmental perturbations and evolutionary
changes in vertebrates and invertebrates were widely reported to have
occurred during the Late Devonian (e.g. House, 1985; McGhee, 1988;
Walliser, 1996; Algeo et al., 1995, 2001; Algeo and Scheckler, 1998;
Caplan and Bustin, 1999; Murphy et al., 2000; Joachimski and
Buggisch, 2002; Goddéris and Joachimski, 2004; Racki, 2005; Bond and
Wignall, 2008; Sallan and Coates, 2010; Sallan and Galimberti, 2015;
Long et al., 2015). Two biotic crises that strongly affected global biota
were the Kellwasser and Hangenberg crises (Buggisch, 1991; Kaiser
et al., 2006, 2008, 2015; Carmichael et al., 2015; Becker et al., 2016);
in addition small-scale events such as the Condroz (Becker, 1993),
Annulata (Becker and House, 1997, 2000; Sandberg et al., 2002; Korn,
2002, 2004; Racka et al., 2010; Hartenfels and Becker, 2016a) and
Dasberg events (Hartenfels and Becker, 2009; Hartenfels, 2011; Kaiser
et al., 2011) have been recognized in Frasnian and Famennian succes-
sions (House, 1985, 2002; Walliser, 1996; Table 1). Both the Kellwasser
Crisis (latest Frasnian) and the Hangenberg Crisis (end-Devonian)
caused severe losses of global diversity of many marine and terrestrial
biotic groups (Newell, 1952, 1956, 1963; Raup and Sepkoski, 1982;
McGhee, 1996; McGhee Jr, 2001, 2014; Alroy, 2010; McGhee Jr et al.,
2013; Sallan and Coates, 2010; Friedman and Sallan, 2012; Sallan and
Galimberti, 2015). However, causes for ecosystem changes and di-
versity loss during the Late Devonian are still highly debated (e.g.
Buggisch, 1991; Algeo et al., 1995, 2001; Algeo and Scheckler, 1998;
Sandberg et al., 2002; Riquier et al., 2006; Long et al., 2015) and
concerning vertebrates, this time interval was mainly studied via global
diversity curves (e.g. Sallan and Coates, 2010; Friedman and Sallan,
2012; Sallan and Galimberti, 2015). Therefore, a regional study on the
vertebrate ecosystem including other organisms such as invertebrates
from a locality with detailed stratigraphical and sedimentological in-
formation is needed. The Maïder Basin of the eastern Anti-Atlas is
suitable for this purpose.
The eastern Anti-Atlas of Morocco is well-known for its highly fos-
siliferous outcrops of Devonian marine sedimentary rocks. In recent
years (e.g., Klug et al., 2008, 2016), some stratigraphic intervals of
several localities became known for their Fossillagerstätten qualities
https://doi.org/10.1016/j.palaeo.2017.12.028
Received 30 June 2017; Received in revised form 21 December 2017; Accepted 22 December 2017
⁎ Corresponding author.
E-mail addresses: [email protected] (L. Frey), [email protected] (M. Rücklin), [email protected] (D. Korn), [email protected] (C. Klug).
30
Chapter I: Alpha Diversity and Palaeoecology
Table
1
Summary
ofpossible
causesandeff
ectsofFamennian(Late
Devonian)andTournaisian(earlyCarboniferous)
bio-events
andenvironmentalperturbations.
Bio-event/environmental
changes
Causes
Effects
Regional:Maïder
Global
Regional:Maïder
Global
Kellwasser
(End-Frasnian)
-Dysaerobic
condition
-Highsealevelstands
( WendtandBelka,1991)
-Anoxia
-Sea-levelch
anges
-Dropin
selenium
level
(e.g.Buggisch
,1991;Sandberg
etal.,2002;Bond
etal.,2004;GerekeandSch
indler,2012;Longetal.,
2015)
-Kellwasserfaciesrich
infossils
(WendtandBelka,1991)
-Loss
inmarinebiodiversity
(e.g.McG
heeJr,2014)
Condroz
(earlyFamennian)
-Regression
(WendtandBelka,1991;
Becker,
1993)
-Regression
(Becker,
1993;Beckeretal.,2012)
-Extinctionoffew
ammonoid
genera
(Becker,
1993)
-Extinctionoffew
ammonoid
genera
(Becker,
1993)
Annulata
(Middle
Famennian)
-Hypoxia
toanoxia,dysoxic
-Transgression
( Hartenfels,2011;Hartenfels
andBecker,
2016a,2016b)
-Anoxia
-Transgression
( Walliser,1996;House,1985;Sandberg
etal.,2002;
Joach
imskietal.,2009;Becker,
1993;Hartenfels,
2011;Rackaetal.,2010)
-Mass
occurrence
oftheammonoid
Platyclymenia
-Small-scale
extinctionin
ammonoids
(Korn,2004;
Hartenfels
andBecker,
2016a,2016b)
-Mass
occurence
oftheammonoid
Platyclymenia
-Small-scale
extinction
(Korn,2004)
Dasberg
(Late
Famennian)
-Hypoxic
conditions
-Twotransgressiveevents
( Hartenfels
andBecker,
2009;
Hartenfels,2011)
-Regionalblackshales
-Transgression
(House,1985;Hartenfels
andBecker,
2009)
-Specieslevelextinction
( Becker,
1993;Hartenfels
andBecker,
2009,Kaiseretal.,2015)
-Coincideswithenvironmentalch
anges
(Hartenfels
andBecker,
2009)
Hangenberg
(End-Famennian)
-Anoxia
-Transgressionfollowedbya
regression
(Kaiseretal.,2011,2015)
-Anoxia
-Globalco
oling
-Regression
-Transgressionfollowedbyaregression
-Eutrophication
-Dropin
selenium
level
(e.g.CaplanandBustin,1999;AlgeoandSch
eckler,
1998;Kaiseretal.,2006;Carm
ichaeletal.,2015)
-Extinctionin
invertebrate
groups(m
ostly
ammonoids,
trilobites,
rhynch
onellid
brach
iopods,
bivalves,
rugose
corals)andin
early
gnathostomes(arthodires,
chondrich
thyans)
( Korn,2004;Kaiseretal.,2011)
-Loss
inmarinebiodiversity
-Bottleneck
invertebrates
(e.g.SallanandCoates,
2010;Friedmanand
Sallan,2012;SallanandGalimberti,2015)
Alum
shale
(Lower-middle
Tournaisian)
-Anoxia
-Transgression
( Kaiseretal.,2011)
-Anoxia
-Transgression
( Becker,1993;Jo
hnsonetal.,1985;Siegmundetal.,
2002)
-Ammonoids:
specieslevelextinction
(Kaiseretal.,2015;seealsoKorn
etal.,2002,2007;Beckeretal.,
2006;EbbighausenandBockwinkel,2007)
-Somegroups(corals,trees,fish)affectedbythe
Hangenberg
Crisis,
diversifiedonly
afterthe
Alum
Shale
Event.
(Poty,1999;Deco
mbeix
etal.,2011;
Denayeretal.,2011;Kaiseretal.,2015)
L. Frey et al.
31
Chapter I: Alpha Diversity and Palaeoecology
because of the abundance (“Kondensat-Lagerstätte”) and exceptional
preservation of fossils (“Konservat-Lagerstätte” sensu Seilacher, 1970).
Among those, Madène El Mrakib (Maïder Basin; cf. Wendt, 1985;
Wendt and Belka, 1991; see Fig. 1, Fig. 3) became famous for its wealth
and diversity of remains of well-preserved invertebrates such as ce-
phalopods (Petter, 1959, 1960; Korn, 1999; Becker, 1995, 2002; Becker
et al., 2000, 2002; Korn and Klug, 2002; Klein and Korn, 2014; Korn
et al., 2014, 2015a, b, 2016a, b; Hartenfels and Becker, 2016a, b; Klug
et al., 2016; Korn and Bockwinkel, 2017), crinoids (Klug et al., 2003;
Webster et al., 2005), brachiopods (Sartenaer, 1998, 1999, 2000) and
trilobites (Struve, 1990). Vertebrate macroremains are rather rare in
most Devonian strata of Morocco, but they become more abundant in
sediments of Late Devonian age. Particularly, three-dimensionally
preserved remains of various Late Devonian (Frasnian and Famennian)
species, mostly of placoderms, from the eastern Anti-Atlas have been
described during the last decades (Lehman, 1956, 1964, 1976, 1977,
1978; Lelièvre and Janvier, 1986, 1988; Lelièvre et al., 1993; Rücklin,
2010, 2011; Rücklin et al., 2015; Rücklin and Clément, 2017). Remains
of other gnathostome groups such as actinopterygians, acanthodians
and chondrichthyans are restricted to microremains, fin spines or iso-
lated jaws (Termier, 1936; Lehman, 1976; Derycke, 1992; Hampe et al.
2004; Derycke et al., 2008; Ginter et al., 2002; Klug et al., 2016;
Derycke, 2017). In several middle Famennian layers of the Maïder
Basin, we recently discovered new, often articulated skeletons of gna-
thostomes such as placoderms, actinopterygians, sarcopterygians and
chondrichthyans, which will strongly improve the knowledge of this
Devonian Konservat-Lagerstätte and thus the palaeoenvironment of this
small marine basin.
In order to better understand Late Devonian ecosystems of the
Maïder through time, we studied alpha diversity and palaeoecology of
the gnathostomes and invertebrates of a series of sufficiently fossili-
ferous strata. Our aim is to answer the following questions: (1) How did
the ecosystem change during the Famennian in the Maïder? (2) Which
groups of gnathostomes were present in the assemblages and were their
occurrences related to invertebrate diversity? (3) What were the effects
of global ecological changes and events on the composition and fluc-
tuations in these assemblages?
2. Material and methods
2.1. Geological setting
Konservat-Lagerstätten conditions prevailed in wide areas of the
Maïder Basin (northeastern Anti-Atlas, Morocco) during the Famennian
(Fig. 1); only south of Tafraoute, exceptionally preserved fossils have
not been found yet. We discovered two layers containing exceptionally
Fig. 1. Geological map of the Maïder and Tafilalt region in the eastern Anti-Altas of Morocco. Localities with phyllocarid layer containing well-preserved remains of gnathostomes are
marked here; faunal changes have been studied from lower to upper Famennian at Madène el Mrakib and from lower to middle Tournaisian at Aguelmous. New data about vertebrate
diversity has been compared to the locality Filon 12 of the Tafilalt region.
L. Frey et al.
32
Chapter I: Alpha Diversity and Palaeoecology
preserved vertebrate fossils, particularly chondrichthyans, in the
Maïder: The middle Famennian (Maeneceras horizon) phyllocarid layer,
named after its high abundance of phyllocarids, contains most of the
gnathostome remains preserved in ferruginous nodules while in the
second layer (early-middle Famennian) fewer remains were found so far
(Fig. 2). A third layer with prevailing Konservat-Lagerstätten conditions
(latest Famennian, Hangenberg Black Shale equivalent) bearing mostly
macroinvertebrates and rarely acanthodian teeth has recently been
documented by Klug et al. (2016).
The phyllocarid layer crops out at various localities such as Bid er
Ras, Jebel Oufatene, Mousgar, Tizi Mousgar, Aguelmous Azizaou, Oued
Chouairef, Tizi n'Aarrat Chouiref and Madène El Mrakib (Fig. 1).
Fig. 2. Positions of the Famennian samples collected from Madène el Mrakib within the global and regional condodont zonations (Ziegler and Sandberg, 1984 and Hartenfels, 2011) and
ammonoid horizons (Becker et al. 2002; Korn et al., 2014). Asterisks and bars mark the approximate position of the samples.
L. Frey et al.
33
Chapter I: Alpha Diversity and Palaeoecology
However, in many of these localities, the sedimentary succession of the
Famennian strata is partially covered by scree, often delivered from the
overlying massive sandstone of the Fezzou Formation which is an
equivalent to the Hangenberg Sandstone of the Tafilalt (Kaiser et al.,
2011; Klug et al., 2016). The Famennian succession is best exposed at
Madène el Mrakib in the southern Maïder because of large scale folding
and erosion towards the Maïder Valley and Tafraoute. Therefore, we
measured a section at this locality from strata of latest Frasnian age
(“Upper Kellwasser Event”) up to the Hangenberg Black Shale equiva-
lent (Rücklin, 2010, 2011; Klug et al., 2016).
Fig. 3. Famennian invertebrate and gnathostome remains from the Maïder. A – B – Bactrites sp., lateral and septal view, ×2, PIMUZ 34012. C – D – Falcitornoceras falciculum, lateral and
ventral views, ×3, PIMUZ 34014. E – F – Ch. (Staffites) afrispina, lateral and ventral views, ×1, PIMUZ 34015. G – H – Planitornoceras pugnax, lateral and ventral views, ×2, PIMUZ
34013. I – J – Platyclymenia annulata, lateral and ventral views, ×1, PIMUZ 34010. K – L – Pseudoclymenia sp., lateral and ventral view, ×1.5, PIMUZ 34011. M – N – Aulatornoceras sp.,
lateral and ventral view, ×1.5, PIMUZ 34016. O – Glyptohallicardia sp., lateral view, ×2, PIMUZ 34017. P – Prosochasma sp., lateral view, ×0.75, PIMUZ 34018. Q – Guerichia sp., lateral
view, ×3, PIMUZ 34019. R – S – Loxopteria sp., lateral views, ×1, PIMUZ 34020. T – U – Paleoneilo sp., lateral and dorsal view, ×2, PIMUZ 34021. V – X – undetermined gastropod,
apical, apertural and basal view, ×2, PIMUZ 34022. Y – Z – undetermined gastropod, apical and apertural view, ×2, PIMUZ 34023. AA – AC – undetermined bellerophontid, lateral,
dorsal and apertural view, ×2, PIMUZ 34024. AD – AH – Phacoiderhynchus antiatlasicus, lateral, dorsal, posterior, ventral and anterior views, ×0.75, PIMUZ 34025. AI – AM –
undetermined brachiopod, lateral, dorsal, posterior, ventral and anterior views, ×1, PIMUZ 34026. AN – Rugose coral, lateral view, ×1.5, PIMUZ 34027. AO – Moroccocrinus ebbigh-
auseni, lateral view, ×1, PIMUZ 34028. AP – Phoebodus sp., labial and aboral view, scale bar= 5mm, PIMUZ A/I 4656. AQ – cladodont shark tooth, lingual view, scale bar= 10mm,
PIMUZ A/I 4657. AR – cladodont shark tooth, labial and oral view, scale bar=5mm, PIMUZ A/I 4658.
L. Frey et al.
34
Chapter I: Alpha Diversity and Palaeoecology
Fig. 4. Changes in diversity and ecospace use during the Famennian at Madène el Mrakib. A – Histograms represent the number of species per association and the changes in diversity
(Table S1). Intervals without histograms often contained rare and/or weathered and compressed fossils which were mostly impossible to determine to the species level. These intervals
were not included in the analysis as they would have resulted in biased species numbers. B – Ecospace expansion (ecological classification after Bush et al., 2007) shows change in the
number of three-dimensional modes of life along the section. C – Changes in gnathostome diversity and composition. Abbreviations of ecological categories: Tiering – p: pelagic, er: erect,
su: surficial, smi: semi-infaunal, si: shallow infaunal; Motility – ff: freely fast, fs: freely slow, fu: facultative unattached, fa: facultative attached, nu: non-motile and unattached, na: non-
motile and attached; Feeding mechanism – sf: suspension feeder, df: deposit feeder, g: grazer, pr: predators.
L. Frey et al.
35
Chapter I: Alpha Diversity and Palaeoecology
2.2. Collection of alpha diversity data
Twelve successive fossil assemblages containing 3591 specimens of
macroinvertebrates (Figs. 3, 4A: associations A-I, K, P-Q; Table S1) co-
occurring with gnathostome remains were collected from the Fa-
mennian of Madène el Mrakib to examine changes in alpha diversity
and palaeoecology. To achieve an adequate resolution in species
abundance and composition and to reduce biases from differences in
sample size, only horizons yielding at least 100 specimens were sam-
pled. Most associations contain numerous formerly pyritized specimens
(now limonitic and haematitic caused by deep weathering of the sedi-
ments) whereas other associations are preserved in limestone nodules,
sideritic nodules and marly beds. In the latter case, specimens were
counted in situ on a bedding plane, depending on the outcrop condi-
tions. To complement our data, we examined 3458 specimens of three
middle Famennian (Platyclymenia and Procymaclymenia horizons) and
two late Famennian (Gonioclymenia to Wocklumeria horizons) samples
from Madène el Mrakib that are housed in the Museum für Naturkunde
in Berlin (Fig. 2: associations J, L-O; Table S1; biozonation is figured in
Korn et al., 2014). This material contains mostly ammonoids and was
published by Korn et al. (2014, 2015a). In addition to the Famennian
samples A to Q from Madène, we examined four samples R to U (Table
S1) containing another 2779 specimens of Early to Middle Tournaisian
(Early Carboniferous) age from Aguelmous. The ammonoids of these
samples were published by Ebbighausen and Bockwinkel (2007).
The ages of the associations were determined by ammonoids (cf.
Korn, 1999; Becker et al., 2002; Korn et al., 2014). For some associa-
tions (A–C, E, G–U in Table S1), a correlation between ammonoid
horizons and conodont zones was possible (Fig. 2; Hartenfels 2011).
The conodont biozonation of the Famennian was recently revised
(Kaiser et al., 2009; Spalletta et al., 2017). However, for the correlation
of our data to global and regional sea level curves (Wendt and Belka,
1991; Haq and Schutter, 2008; Kaiser et al., 2011), we used the pre-
vious conodont zonation of Sandberg et al. (1978) and Ziegler and
Sandberg (1984).
The fossils were determined at species level wherever possible and
subsequently, the relative abundance of every taxon was calculated and
plotted as histograms per association. Moreover, the trophic nucleus
concept of Neyman (1967) was applied to our abundance data to detect
taxa that were dominating each fauna. The trophic nucleus includes
taxa whose relative abundances contribute to 80% of the total abun-
dance of all taxa of a fauna. Additionally to the analysis of the alpha
diversity of complete samples, we counted ammonoid genera of every
association because some middle and upper Famennian samples ex-
clusively contained cephalopods when considering macrofossils only. In
order to compare samples of different sample sizes and to avoid biases
caused by different methods or by varying sampling efforts to each
other, we rarefied the abundance data of each fauna with the software
package PAST (Hammer et al., 2001).
2.3. Ecospace occupation
Analyses in palaeoecology are based on the theoretical ecospace
concept sensu Bush et al. (2007). We grouped all taxa according to
ecological categories of “tiering”, “motility” and “feeding mechanism”.
The combination of these three ecological parameters leads to a unique
three-dimensional mode of life per taxon. ‘Tiering’ categorises the po-
sition of organisms in the water column such as pelagic, erect, surficial,
semi-infaunal and shallow or deep infaunal. We assigned all cephalo-
pods such as ammonoids, bacritids and orthocerids to a pelagic lifestyle.
The habitat of fossil phyllocarid crustaceans is still a matter of debate.
Due to the ferruginous sediments (probably due to pyrite weathering;
the pyrite points at low oxygen conditions) in the Maïder Basin, we
assigned the phyllocarids to a nektobenthic or pelagic mode of life as it
was proposed before by several authors (e.g. Siveter et al., 1991;
Vannier and Abe, 1993; Zatoń et al., 2013). Nevertheless, it has to be
considered that recent benthic phyllocarids are able to survive short-
term anaerobic conditions and that this tolerance might have existed in
extinct taxa as well (Vannier et al., 1997). Besides the crinoid Mor-
occocrinus ebbighauseni that was probably pseudoplanktonic in early to
middle ontogenetic stages and perhaps benthic in adult stages (Klug
et al., 2003; Webster et al., 2005), we found one specimen of a crinoid
holdfast in one of the associations, which might be benthic and erect
(unless it was attached to a living ammonoid). All gastropods (Macro-
chilina), amphigastropods (Bellerophon), brachiopods (rhynchonellids,
Aulacella), rugose corals and trilobites in the samples inhabited the
sediment surface (Bush et al., 2007). Cladochonid-type tabulate corals
(Webster et al., 2005) are lacking in our samples of Madène el Mrakib.
The lifestyle of bivalves is highly diverse and it is still not completely
clarified for all fossil taxa. Species of the genera Guerichia, Prosochasma,
Opisthocoelus, Ptychopteria and Streblopteria were probably living on the
sediment surface (Amler, 1996, 2004, 2006). Amler (2004) assumed
that small bellerophontids, gastropods and the bivalve genus Guerichia
could have lived on erect benthic or floating algal thalli and therefore,
their occurrence was not limited to the sea floor (oxygen-poor condi-
tions cannot be ruled out). We determined these organisms as surficial
because we found only little organic matter in our section and the ha-
bitat might have been too deep for large benthic algae (estimated depth
at Madène el Mrakib is around 200m and therefore below the euphotic
zone; Tessitore et al., 2016). Epibenthic to semi-infaunal lifestyles were
proposed for the bivalve Buchiola (Buchiola) and Glyptohallicardia
(Grimm, 1998) whereas Loxopteria might have been semi-infaunal
(Nagel, 2006). Paleoneilo and Metrocardia as well as lingulid brachio-
pods have been suggested to be shallow infaunal based on actualistic
comparisons (Thayer and Steele-Petrovic, 1975; Amler, 1996; Kříž,
2004). Bivalve species that we could neither determine nor assign to
modes of life, we summarized as ‘benthic organism’ in a separate ca-
tegory.
‘Motility’ refers to locomotory capabilities of organisms such as
freely, fast or slow motile, attached or non-attached facultatively motile
or completely non-motile. We assigned phyllocarids and trilobites to
freely, fast motile organisms (Vannier et al., 1997; Fortey, 2004),
whereas cephalopods and gastropods were rather slow motile organ-
isms (Westermann, 1999; Westermann and Tsujita, 1999). Rugose
corals, crinoids, brachiopods and the bivalve genera Guerichia, Pty-
chopteryia and Streblopteria were non-motile organisms attached to their
substrate whereas Prosochasma and Opisthocoelus were attached as well
but facultatively motile (Bush et al., 2007; Amler, 1996, 2004; Nagel,
2006; Kříž, 2004). Buchiolid bivalves were sessile and unattached
(Grimm, 1998).
‘Feeding mechanism’ describes whether animals acquire food by
predation, mining, grazing suspension filtering or deposit feeding. For
cephalopods, we assume this group to be microphagous predators (Klug
and Lehmann, 2015). Brachiopods, rugose corals, crinoids and most
bivalves were suspension feeders (Paleoneilo represents a deposit feeder;
Amler, 2004) while gastropods were assigned to grazers. The phyllo-
carids of the Maïder were suspension feeders as they were probably
pelagic due to the dysoxic sediments and poor benthic bottom life.
Trilobites had a high variety in acquiring food including feeding on
plankton and organic particles, scavenging or preying on small organ-
isms on or near the bottom (Fortey and Owens, 1999; Fortey, 2004). On
the one hand, the trilobites in our sample were rather small benthic
forms that possibly were deposit feeding. On the other hand, they look
morphologically similar to forms (e.g. big eyes for good vision, Fortey,
2004) that were scavengers or also microphagous predators.
3. Results
3.1. Fluctuations in invertebrate diversity
In total, the 21 associations contain 9828 specimens that were as-
signed to around 227 species (Tables S1, S3). Since we separately
L. Frey et al.
36
Chapter I: Alpha Diversity and Palaeoecology
Fig. 5. Species abundances of 11 successive faunal samples of early to late Famennian age from Madène el Mrakib in the Maïder region (Morocco); red bars represent the dominant
species of each association. A – association A, early Famennian, all three sampled taxa are shown. B – association B, early Famennian, all four sampled taxa are shown here. C – association
C, early Famennian, nine of thirteen taxa are shown. D – association D, middle Famennian, all five sampled taxa are shown here. E – association E, middle Famennian, five of eight taxa
are shown here. F – association F, middle Famennian, eight of eleven taxa are shown here. G – association G, middle Famennian, four of nine taxa are shown here. H – association H,
middle Famennian, seven out of fourteen taxa are shown here. I – association I, middle Famennian, Annulata event layer, all two sampled taxa are shown here. J – association K, middle
Famennian, 11 out of 22 sampled taxa are shown here. K – association Q, late Famennian, Hangenberg Black Shale, five out of eleven sampled taxa are shown here. Not depicted species
are listed in Table S3. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
L. Frey et al.
37
Chapter I: Alpha Diversity and Palaeoecology
analyzed ammonoids and the complete assemblages of selected layers,
the entire assemblage is concerned when we write of species; ammo-
noid diversity is separately depicted and indicated. During the early
Famennian (Cheiloceras horizon), the general species richness increases
from three up to twelve species and one to five ammonoid genera were
counted within this interval (Fig. 4A: association A–C; Fig. 5A–C). The
middle Famennian phyllocarid layer (Maeneceras horizon) contains
numerous gnathostome remains (Fig. 4: association E; Fig. 5E) and
eight species of invertebrates including two ammonoid genera. In the
following middle Famennian associations (Maeneceras to Planitorno-
ceras horizon), 11 to 14 species and one to four ammonoid genera were
present (Fig. 4A, associations F–H; Fig. 5F–H). We found two cepha-
lopod species and one ammonoid genus in the Annulata Black Shales
(middle Famennian, Platyclymenia horizon) whereas in the subsequent
sample, 24 ammonoid species and five ammonoid genera were counted
(Figs. 4I, 7, Table S1: association I-J). In the following sample above the
Annulata Black Shales, species richness reaches 22 species comprising
six ammonoid genera (Fig. 4A: association K; Fig. 5J). In the two other
samples of the middle Famennian (Platyclymenia/Procymaclymenia
horizon), thirteen and nine species were counted and in both samples,
seven ammonoid genera were present (Fig. 7: associations L–M). In the
latest Famennian (Gonioclymenia to Wocklumeria horizons), 13 species
including seven ammonoid genera and three species including one
ammonoid genus were counted (Fig. 7: association N–O). Nine taxa
were found so far in the Wocklumeria horizon (latest Famennian;
however, these layers are not yet sufficiently sampled to provide ac-
curate abundance data (Figs. S1, 4A: association P). In the Hangenberg
Black Shale equivalent (latest Famennian), eleven species containing
four ammonoid genera were found (Fig. 4A, association Q; Fig. 5K). The
earliest Tournaisian association (Fig. 6A) is diverse containing 32 spe-
cies (thereof eight ammonoid genera) while the other three Tournaisian
associations contained eight to fifteen species including two to seven
ammonoid genera (Fig. 6B–D; Table S1, association R–U).
We estimated the sampling bias caused by differences in the method
and duration of sampling by rarefaction analysis. The rarefaction curves
describe the number of taxa that could have been collected with ex-
tending the sampling duration (increasing number of specimens). Some
graphs show steep curves that mean more taxa would have been found
with further collecting within some of the samples (Figs. S2, S3).
However, the biased samples still show low species numbers compared
with the most diverse samples regarding the species numbers that could
have been found within a certain number of collected specimens (we
checked for 90 specimens in each graph). Therefore, trends in diversity
are not strongly biased and here considered reliable; nevertheless, it
cannot be ruled out that these results are influenced by faunal mixing to
a small extend (e.g., Kidwell and Bosence, 1991); indicators for strong
condensation, such as eroded and reworked fossils, very reduced
thickness, extensive hiatuses and iron crusts, are absent.
3.2. Changes in the trophic nucleus
Cephalopods such as ammonoids and orthocerids are the most im-
portant components of the trophic nucleus in some early, middle and
late Famennian samples (Fig. 5B, F, H, J) or were even the only
dominant group (Fig. 5C–D, G, J). Phyllocarids occur only in one
sample but in great abundance and thus are dominant at Madène el
Mrakib (Fig. 5E). Brachiopods and bivalves contributed rarely to the
trophic nucleus except for in a middle Famennian sample and in the
Hangenberg Black Shale equivalent (Fig. 5A, F, H). In the Tournaisian
associations, ammonoids mainly constitute the trophic nucleus except
for one single gastropod species that is present in the oldest Tournaisian
association (association R in Fig. 6A).
3.3. Ecospace occupation during the Famennian
In the early Famennian (Cheiloceras horizon) associations, two to
three modes of life were present and pelagic lifestyles had higher re-
lative abundance than benthic lifestyles (67 versus 33%; Fig. 4B; as-
sociation A–C). The middle Famennian phyllocarid layer (Maeneceras
horizon) contains taxa dominated by pelagic lifestyles and taxa with an
additional mode of life (freely pelagic, fast motile deposit feeders that
are represented by phyllocarids) were found. By contrast, the next
younger association yielded a high relative abundance of benthic modes
of life (82%), which stays high (46–68%) in the following middle Fa-
mennian associations (F–H). The association of the Annulata Black
Shales represents only pelagic modes of life, while the association above
the Annulata Black Shales (Platyclymenia/Procymaclymenia horizon)
contains seven modes of life represented by benthic and pelagic or-
ganisms (freely pelagic, slow-motile predators having the highest
abundance, 57%). In the latest Famennian (Gonioclymenia to Wocklu-
meria horizon), pelagic, freely motile predators were highly abundant
(92%). However, samples were biased towards cephalopods and
therefore, they were excluded from this analysis. The Wocklumeria
horizon (latest Famennian age, association P) contained organisms of
four modes of life and benthic organisms had a high relative abundance
(75%) in comparison to pelagic forms (25%). In the following Hang-
enberg Black Shale equivalent (association Q), only two modes of life
were present of which the pelagic organisms had the highest abundance
(60%). During the Early Tournaisian, the ecospace of associations R and
S (Aguelmous, Fig. 9C) consists of five modes of life but in the following
two associations (Fig. 9C: associations T and U), the ecospace is reduced
to one single mode of life. In all the Tournaisian associations, pelagic
organisms are more abundant than benthos.
In total, we report here 12 or possibly 13 modes of life (some bi-
valves could not be assigned to certain three-dimensional lifestyles)
from 216 theoretically possible combinations. This value lies below the
middle Palaeozoic (Late Ordovician to Devonian) value of about 21
modes of life known from North America and Europe (Bush et al.,
2007). Nineteen modes of life were recorded in the Early Devonian
strata of the Tafilalt region (Jebel Ouaoufilal, Filon 12, see Fig. 1) that
is palaeogeographically and temporally closer situated to the Late De-
vonian of the Maïder (Frey et al., 2014). The slightly impoverished Late
Devonian ecological diversity of the southern half of the Maïder Basin
points at unfavorable living conditions that coincide with the occur-
rence of reddish ferruginous deposits indicating dysoxic environmental
conditions (Korn, 1999; Korn et al., 2015b; Kaiser, 2005; Webster et al.,
2005).
3.4. Diversity and ecospace use in vertebrates
Skeletal remains of chondrichthyans, sarcopterygians and acti-
nopterygians are restricted to specific layers, while placoderms were
found in many more horizons of the section and in other parts of the
eastern Anti-Atlas (Fig. 4C). The highest abundance and species rich-
ness in gnathostomes was found in the phyllocarid layer (middle Fa-
mennian corresponding to the Maeneceras horizon) containing seven
species, whereas only one to two species occurred in the other layers
(Fig. 8). In this layer, we found three species of placoderms (Dunk-
leosteus, Driscollaspis sp. nov., and a second undescribed placoderm n.
gen. et sp.), chondrichthyans (Phoebodus sp., two undescribed clado-
donts) and one actinopterygian (work in progress). Approximately 20m
above the phyllocarid layer, remains of cladodont chondrichthyans
were found, while the sarcopterygians were found six meter below the
Annulata Black Shales (Fig. 4C). Further skeletal remains of Dunkleos-
teus occurred in the late middle Famennian strata and a co-occurrence
of Titanichthys and Dunkleosteus was found in layers of late Famennian
age. The Hangenberg Black Shale equivalent yielded small teeth of
ischnacanthid acanthodians (Klug et al., 2016).
The ecospace use of the gnathostomes of the Maïder Basin is
homogenous. Placoderms such as Dunkleosteus and Titanichthys as well
as cladodont chondrichthyans are assumed to have been pelagic ani-
mals (Ginter et al., 2010; Carr, 2008, Carr and Jackson, 2008; Long &
L. Frey et al.
38
Chapter I: Alpha Diversity and Palaeoecology
Trinajstic, 2010). The two additional placoderm species are assumed to
have lived in the water column as well because they do not show mouth
parts specialized for crushing hard shelled prey. Phoebodont chon-
drichthyans inhabited a narrower range of environments (“moderately
deep to moderately shallow waters”; Ginter et al., 2010). Onychodus
was reported from the inter-reefal basin of the Gogo Formation
(Playford, 1980; Andrews et al., 2006; Long and Trinajstic, 2010) and
therefore, the onychodont sarcopterygians of Madène might have been
living in the water column as well. Most of these gnathostomes have
been assumed to have been preying on other vertebrates or in-
vertebrates such as phyllocarids, cephalopods as well as conodonts
(e.g., Jaekel, 1919; Miles, 1969; Williams, 1990; Mapes et al., 1995,
Zatoń et al., 2017). An exception is the placoderm Titanichthys that was
supposedly a filter feeder because of its long jaw plates with rounded
cross section (Denison, 1978).
4. Discussion
4.1. Invertebrate diversity, ecospace occupation and trophic nuclei during
the Famennian
Examination of alpha diversity, taxonomic composition and eco-
space occupation shows that environmental conditions at Madène el
Mrakib were mostly oxygen-depleted during much of the Famennian.
The faunal composition often includes opportunistic species that were
tolerant to oxygen depletion (Guerichia, buchiolid bivalves, small veti-
gastropods and bellerophontids, Chondrites; Wignall and Simms, 1990;
Amler, 1996, 2004) and deep-water species (e.g. the brachiopods Au-
lacella and Phacoiderhynchus as well as the bivalve Loxopteria;
Sartenaer, 2000; Nagel-Myers et al., 2009). Occurrences of pelagic and
opportunistic taxa as well as fluctuant environments (several trans-
gressions within a larger regressive cycle) in the Famennian were re-
ported from the Maïder Basin (Becker 1993; Hartenfels and Becker,
2009; Hartenfels, 2011; Hartenfels and Becker, 2016a, b) as well as
from localities outside Morocco (Dreesen et al., 1988; Becker and
House, 1997; Sandberg et al., 2002; Kaiser et al., 2006; Marynowski
et al., 2007; Joachimski et al., 2009; Racka et al., 2010).
Fig. 6. Abundances of species and faunal composition of early and middle Tournaisian associations from Aguelmous (Maïder region); data and bed numbers were taken from the
collection of Ebbighausen & Bockwinkel (2007); red bars represent dominant taxa. A – association R, early Tournaisian association, 17 out of 32 sampled taxa are shown here. B –
association S, early Tournaisian association, all eight sampled taxa are shown here. C – association T, early Tournaisian association, all 15 sampled taxa are shown here. D – association U,
middle Tournaisian association, all the nine sampled taxa are shown here. Not depicted species are listed in Table S3. (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article.)
L. Frey et al.
39
Chapter I: Alpha Diversity and Palaeoecology
4.1.1. Early Famennian
In this time interval at Madène el Mrakib, the predominant presence
of brachiopods and the increase in ammonoid diversity can be ex-
plained by a regionally high sea level (Wendt and Belka, 1991) (Fig. 4A:
associations A–C; Fig. 9A–C). Abundant early Famennian rhynchonellid
brachiopods were also reported from the East European Platform and
they were often flourishing during major transgressions (Sokiran,
2002). Similar associations containing abundant cephalopods and bra-
chiopods were reported from the early Fammenian Pa. crepida and
rhomboidea zones of the Holy Cross Mountains (Racki, 1990). During
this time interval, the ecosystem recovered from the Kellwasser Crisis
that caused great structural changes within the marine ecosystem
(Becker, 1986; Droser et al., 2000). However, oxygen-poor conditions
likely persisted from the Frasnian well into the Famennian, as reflected
by the widespread Kellwasser Facies characterized by fossiliferous,
black bituminous early Famennian limestones and claystones in the
Anti-Atlas (Figs. 4, 9; Wendt and Belka, 1991). We did not detect the
Condroz event,which coincides with a regression (sea level curves in
Fig. 9), perhaps due to insufficient sampling. Probably this interval was
covered by scree at Madène el Mrakib (see stratigraphy in Fig. 4).
4.1.2. Middle Famennian
During the middle Famennian, species richness varies between six
and fourteen species (Fig. 4A, associations A–H) in our samples. The
ecospace occupation fluctuates between three and seven modes of life
and the proportion between benthic and pelagic lifestyles is varying
(between 33% and 82%) in these associations. Changes in the compo-
sition of the associations reflect fluctuations in the level of oxygenation
at the seafloor, which, in turn, coincide with global rather than regional
sea level changes (Fig. 9). For instance, the widest extension of eco-
space use (including several benthic lifestyles represented by relatively
large and epibenthic bivalves and the contemporary decrease in am-
monoid diversity; Figs. 4B, 9C, association F) indicates an increased
ventilation of the seafloor that correlates with a global regression
(global sea level curve in Fig. 9; Haq and Schutter, 2008; Becker et al.,
2012). The faunal signals appear to coincide with eustatic rather than
with regional sea-level changes; therefore, we assume that the Fa-
mennian sea level of southern Morocco (Wendt and Belka, 1991) is
more fluctuant than previously reported by these authors (regional sea
level curve in Fig. 9). This is not so surprising when the configuration of
the Maïder Basin is taken into account. Towards the northwest and
southeast, it was surrounded by land and in the West and East by to-
pographic highs, namely the marine Maïder Platform and the Tafilalt
Platform (Wendt, 1985; Kaufmann, 1998). This area of shallower water
limited the water exchange between the two basins; this implies a
further reduction of water exchange during eustatic sea-level low-
stands. By contrast, during lowstands, some areas might have been
more oxygenated because wave action reached closer to the sediment
surface. Another factor we have not assessed yet is the influence of fresh
water from the surrounding land. The existence of rivers is documented
by local occurrences of fine clastic sediments and trunks of Archae-
opteris in the Maïder and Tafilalt Basins (Wendt and Belka, 1991).
4.1.3. Middle Famennian Annulata black shales
During the deposition of the Annulata Black Shales, the ecosystem
was depleted with only two species represented by nektonic cephalo-
pods only at Madène el Mrakib. However, 25 species of cephalopods
(including seven ammonoid genera) were previously reported from the
entire Platyclymenia horizon of the Maïder (Korn, 1999; Korn et al.,
2014, 2015a, b; Fig. 7: association J; Fig. 9A; Table S1). Hartenfels and
Becker (2016a) reported some benthic taxa from the Lower Annulata
Event interval of Mrakib such as small gastropods and guerichid bi-
valves. The dominance of pelagic taxa in our section of Madène el
Mrakib and the possible occurrence of benthos tolerant to oxygen de-
pletion indicates anoxic to dysoxic conditions at the bottom caused by a
global transgression (Haq and Schutter, 2008; Hartenfels, 2011;
Hartenfels and Becker, 2016a). Anoxic conditions during the deposition
of the Annulata Black Shales were reported from geochemical analyses
of southern Poland as well, although they were interrupted by a better
oxygenated phase (Racka et al., 2010). Annulata Black Shales with oc-
currences of pelagic species and the opportunistic bivalve Guerichia
were reported worldwide (Becker, 1993; Becker and House, 1997; Sanz-
López et al., 1999; Becker and House, 2000; Sandberg et al., 2002;
Korn, 1999, 2002, 2004; Becker et al., 2004; Hartenfels et al., 2009;
Hartenfels and Becker, 2016a).
Bio-events do not always strongly affect the ecospace: e.g., the
global species richness in bivalves was affected while the ecological
diversity stayed stable throughout Earth's history (Mondal and Harries,
2016). However, on the regional scale and including higher time-stra-
tigraphic resolution and different invertebrate groups, ecospace might
be more variable. The ecospace use can quickly change as well; for
example, the association that follows the Annulata Black Shales is quite
diverse, thus reflecting a rapid recovery of the biota corresponding to a
global and rapid drop of the sea level (22 species including several
benthic lifestyles and abundant ammonoids are present; Figs. 4A, 9A, C:
Fig. 7. Number of ammonoid genera per association. Associations A–Q were collected
from the Famennian of Madène el Mrakib, associations R–U were sampled from the
Tournaisian of Aguelmous.
L. Frey et al.
40
Chapter I: Alpha Diversity and Palaeoecology
association K). The biota recovered faster than after the Kellwasser
Crisis, probably because the Annulata Event caused less profound eco-
logical changes. Diversity data of the complete invertebrate associa-
tions are missing from the overlying middle Famennian interval.
However, three ammonoid-based samples show that at least in this
group, no major changes were occurring (five to seven genera are
present) and therefore, environmental conditions might have stayed
similar.
In the late Fammenian parts of our section at Madène el Mrakib, we
did not find any black shales corresponding to the Dasberg Crisis at the
transition of the Lower/Middle expansa conodont Zone, although it has
been documented from the Maïder Basin (Becker, 1993; Kaiser et al.,
2008; Hartenfels and Becker, 2009).
4.1.4. Latest Famennian and Hangenberg black shale equivalent
The uppermost Famennian sedimentary succession at Madène el
Mrakib is largely covered by the scree of massive sandstone blocks of
the Fezzou Formation (Hangenberg Sandstone equivalent). In the scree,
we found material of several ammonoid species and only few benthic
organisms. Ammonoid samples (benthos is underrepresented with very
few specimens of nuculid bivalves, rhynchonellid and chonetid bra-
chiopods as well as crinoids) from Madène el Mrakib do not show any
major changes in the Gonioclymenia horizon (seven genera are present
like in the preceding, i.e., slightly older, late Famennian strata; Korn
et al., 2015a; Korn et al., 2016a, b; Table S3). However, only one am-
monoid genus is present in the Kalloclymenia toWocklumeria horizons of
Madène el Mrakib. When comparing collections from other localities in
the Maïder (Lambidia, Tourirt and Bou Tlidat), these comprise seven
ammonoid genera and therefore, some species might have been missed
at Madène el Mrakib due to insufficient sampling effort and the spatial
variation of the fossil record.
The associations of Hangenberg Black Shale equivalent contain a
higher overall diversity including more benthos represented by bivalves
(especially Guerichia elliptica) and bryozoans (but possibly as epizoans
on ammonoids) as well as bioturbation (small and ubiquitous
Chondrites) compared with the Annulata Black Shales (Fig. 4: associa-
tions P–Q; Fig. 9C). The abundance of bioturbation indicates that the
Hangenberg Black Shale equivalent was deposited under hypoxic rather
than entirely anoxic conditions, or at least with varying levels of oxygen
(Klug et al., 2016) at Madène el Mrakib. This finding does not contra-
dict results of geochemical analyses of sections in localities of Morocco
and southern Europe that revealed evidence for anoxia during the de-
position of the Hangenberg Black Shale (Kaiser, 2005, Kaiser et al.,
2006, 2008), because all these benthic organisms (reflected also in the
trace fossils) were likely tolerant towards low oxygen levels at the sea-
floor. Sea-level curves for the Devonian of Morocco show a transgres-
sion during the deposition of the Hangenberg Black Shales followed by
a regression in the overlying Hangenberg Sandstone equivalent (Kaiser,
2005; Kaiser et al., 2011, 2015). Similarly, the global sea level curve
shows a transgression followed by a regression during the Hangenberg
Crisis (Haq and Schutter, 2008).
4.1.5. Early and middle Tournaisian
During the early to middle Tournaisian of Aguelmous, nektonic
cephalopods were flourishing while benthic organisms were rare (bi-
valves, tabulate and rugose corals, gastropods, bellerophontids, bra-
chiopods, spiriferids; Fig. 6, Table S3, association R–U) with some ex-
ceptions in the Maïder and Tafilalt. This is reflected in the scarcity of
strata with abundant bioturbation, but this might be a wrong im-
pression rooting in the fact that the fine-grained siliciclastic sediments
(claystones, siltstones and fine-grained sandstones) are deeply weath-
ered and often covered by scree (personal observation by CK). How-
ever, the samples are biased (sampling) towards ammonoids what is
reflected by the almost parallel curves of the ammonoid genera and
total species richness. Haq and Schutter (2008) reported a sea-level rise
followed by a drop in the sandbergi Zone which could have decreased
the ammonoid diversity at Aguelmous. But the regional sea level (Bou
Tlidat, Kaiser et al., 2011) remained high during this interval and from
several localities of the Tafilalt, a second eustatic transgression was
reported (Lower Alum Shale Event, early/middle Tournaisian
boundary; crenulata biozone), that favored pelagic life (Kaiser et al.,
2008, 2011, 2015). The Lower Alum Shale Event caused extinction in
several groups, however in ammonoids probably only at species level
(Kaiser et al., 2011, 2015; see ammonoid record in Ebbighausen and
Bockwinkel, 2007).
4.2. Diversity and palaeoecology of gnathostomes
Similar to the invertebrates, the Famennian vertebrate diversity of
the Maïder Basin was depleted (placoderms: Dunkleosteus, Titanichthys,
Driscollaspis sp. nov., an undescribed placoderm; chondrichthyans:
Phoebodus sp., two undescribed cladodonts; sarcopterygian:
Onychodontidae; actinopterygian: aff. Moythomasia) (Figs. 4C, 8, 9B).
Previously reported microremains of chondrichthyans from the middle
Famennian (Palmatolepis trachytera and Pa. postera zones) of the Maïder
include similar faunal components (Thrinacodus tranquillus, Stetha-
canthus, possibly Cobelodus, Denaea, undetermined cladodonts) and
pointed at a low diversity as well (Derycke et al., 2008; Derycke et al.,
2014, 2017). The pelagic and highly to moderately mobile predators
(except for the supposedly filter feeding placoderm Titanichthys) pre-
ferably preyed on other pelagic organisms such as cephalopods, fishes
and phyllocarids (Williams, 1990; Mapes et al., 1995) this might ex-
plain the high abundance of gnathostomes (especially chondrichthyans:
23 individuals) in the phyllocarid layer. A co-occurrence of crustaceans
and gnathostomes is known from Frasnian rocks of the Gogo-Formation
of Australia (Briggs et al., 2011) as well as the Cleveland Shale in the
USA (Williams, 1990) and indicates that crustaceans could have been a
nutritive food source for early vertebrates. However, it has to be con-
sidered that the preservational probability was higher in these layers at
these localities as even small phyllocarids have been preserved. The
deposition of the Moroccan phyllocarid layer coincides with a global
regressive cycle showing that the gnathostome preferred an environ-
ment that was shallower and better ventilated. However, when com-
pared to the regional sea-level curve (Fig. 9B), these correlations are not
evident.
Gnathostome abundance and diversity is much lower (one to two
species of placoderms) in the upper parts of the middle and upper
Famennian sedimentary rocks where cephalopods and brachiopods are
most common. Last occurrences of vertebrates, namely two teeth of
ischnacanthid acanthodians, were found in the Hangenberg Black Shale
equivalent of Madène el Mrakib, although the potential for the pre-
servation of vertebrate macroremains is high in these shales (Klug et al.,
2016). Nevertheless, the upper Famennian rocks (Pa. expansa Zone) of
the adjacent Tafilalt region (northeastern Anti-Atlas, Morocco) are rich
in gnathostome microremains (Ginter et al., 2002). Generally, the
middle and upper Famennian carbonates of the Tafilalt region are more
Fig. 8. Species abundance of Famennian gnathostomes in the phyllocarid layer of the
southern Maïder region (northeastern Anti-Atlas, Morocco).
L. Frey et al.
41
Chapter I: Alpha Diversity and Palaeoecology
Fig. 9. Conodont zones (after Ziegler and Sandberg, 1984), ammonoid horizons (after Becker et al., 2002, Korn et al., 2014) and eustatic sea levels of the Famennian and Early
Tournaisian according to Haq and Schutter (2008). Regional sea level is adopted from Wendt and Belka (1991) for the Famennian and from Kaiser et al. (2011) for the Tournaisian.
Arrows mark regional fluctuations proposed by this work here. A – Changes in diversity: invertebrates of Madène el Mrakib and Aguelmous (brown); number of ammonoid genera (blue) B
– Gnathostome diversity of the Maïder (light purple); microremains of the Maïder from Derycke et al. (2008) (dark purple); gnathostomes of the Tafilalt according to Ginter et al. (2002)
and Rücklin and Clément (2017) (orange). Exact positions of vertebrate assemblages within the conodont zones are unknown. C – Changes in pelagic-to-benthic lifestyle ratio within
ecospace at Madène el Mrakib and Aguelmous. Dashed lines: sufficient samples are missing.
L. Frey et al.
42
Chapter I: Alpha Diversity and Palaeoecology
diverse compared to the Maïder Basin in yielding about 17 pelagic and
benthic species of the chondrichthyan genera Jalodus, Thrinacodus,
Phoebodus, Ctenacanthus, Stethacanthus, Symmorium, Cobelodus, Denaea,
Protacrodus, Siamodus, Clairina (Derycke, 1992, 2017; Ginter et al.,
2002). There is a clear difference in preservation of cartilaginous fishes:
more or less complete skeletons in the Maïder versus exclusively mi-
croremains in the Tafilalt. These differences in gnathostome ecology,
diversity and preservation likely resulted from different environmental
conditions between the two regions. The Maïder Basin was deeper than
the Tafilalt pelagic ridge and the western part of the Tafilalt Basin and
was isolated from the open ocean by land and shallow marine areas
(Wendt, 1985, 1995; Wendt et al., 2006; Fröhlich, 2004; Lubeseder
et al., 2010) and therefore, the Maïder Basin and especially its bottom
waters were not well ventilated at all times. These conditions could
explain the poor diversity in invertebrates (especially benthos) and
vertebrates. Additionally, this partially explains the preservation of
articulated vertebrate skeletons as strong currents and scavengers were
rare or absent close to the sediment surface.
In the Tournaisian (Early Carboniferous), neither the Maïder nor the
Tafilalt was rich in vertebrates. This is in accordance with the global
fossil record of vertebrates. With a few exceptions (Alekseev et al.,
1994), early Tournaisian vertebrates are globally rare and even the
extremely diverse late Famennian gnathostome fauna of the Cleveland
Shales vanished entirely (Hansen, 1996; Friedman and Sallan, 2012).
Environmental perturbations during the late Famennian might have
strongly affected the ecosystem but the environment in the Tournaisian
itself was probably not suitable for a diverse gnathostome ecosystem.
Living conditions were probably suitable for some pelagic but not for
benthic gnathostomes due to high sea levels, and an environment
dominated by pelagic cephalopods.
It has to be considered that the biota reacted not only to abiotic but
indirectly also to biotic changes. Biotic factors as causes for changes in
ancient ecosystem are often dismissed because direct evidence of botic
interactions (e.g. stomach contents) are rarely preserved (Williams,
1990; Martill et al., 1994; Cavin, 1996; Richter and Baszio, 2001;
McAllister, 2003; Kriwet et al., 2008; Sallan et al., 2011; Zatoń et al.,
2017; Chevrinais et al., 2017).
In the case of the Famennian and Tournaisian of the Maïder, pre-
vailing anoxic to dysoxic conditions at the seafloor likely limited ben-
thonic life (primary consumers), important food source for small fishes
(secondary consumers), which, in turn, represent prey for bigger fishes
such as predatory placoderms and chondrichthyans (third level con-
sumers). Moreover, the missing predation pressure by gnathostomes on
the ammonoids during the early Tournaisian might have fostered the
rapid re-diversification of ammonoid taxa. Patterns like this were de-
scribed from early Carboniferous crinoids that diversified after the ex-
tinction of their predators (Sallan et al., 2011). However, work on
higher stratigraphic resolution and comparisons among different lo-
calities have to be carried out in order to test the assumed relationship
between extinction of predators and a subsequent radiation of ammo-
noids.
Moreover it is hardly assessable to what extend regional migration
patterns influenced the biota of the Maïder and therefore, if the regional
diversity and ecological trends can be fully assigned to the global
ecosystem.
5. Conclusions
Quantitative analyses of 21 invertebrate associations from the
Famennian to middle Tournaisian sedimentary rocks of the Maïder
Basin document an ecosystem mostly dominated by pelagic in-
vertebrates (particularly cephalopods) and gnathostomes (phoebodont
and cladodont chondrichthyans, placoderm such as Dunkleosteus and
Titanichthys). The ecospace extension of invertebrates reacted to eu-
static and/or regional sea-level changes that caused fluctuations in
ventilation and thus, oxygenation of the seafloor. Based on the variable
occurrence of benthic lifestyles, we propose that changes in regional
sea-level and their effects were stronger than previously thought; this
applies in particular to the beginning of the middle Famennian and
around the Annulata Black Shales. A fluctuating sea level is also sup-
ported by changes in sedimentological composition (alternating clay,
marls and nodular limestone) in the Maïder.
Reduction of ecospace occupation (especially in benthic lifestyles)
occurred after and during bio-events: The slightly recovered biota after
the Kellwasser crises was strongly affected during the late Famennian,
which is reflected in a low ecological diversity (two modes of life)
during the deposition of the Annulata Black Shales. Although the biota
recovered rapidly from this bio-event (seven modes of life), the ecolo-
gical diversity declined again during the Wocklumeria horizon and the
Hangenberg Crisis (five and two modes of life). The biota did not re-
cover very quickly from these crises and ecological depletion persisted
during the early Tournaisian.
Attention should not solely be paid to big events (Kellwasser and
Hangenberg crises) but also to small-scale environmental changes (e.g.
Condroz, Annulata and Dasberg events) as well as other environmental
and ecological changes during the Famennian. Unstable biota fluctu-
ating in numbers of species and modes of life might have been affected
even more strongly by mass-extinctions than biota in stable ecosystems.
It is hardly assessable how the changes in environmental conditions and
invertebrate ecology affected the accompanying vertebrates due to the
comparably low diversity and abundance of gnathostomes in the
Maïder Basin (except for the phyllocarid layer where phyllocarids were
abundant and likely a suitable prey). Nevertheless, biotic interactions
are probable and strong fluctuations in the abundance and diversity of
primary consumers (invertebrates) disturbed the local food web and
represent the likely explanation for the limited abundance and diversity
of secondary and third level consumers (gnathostomes). In order to
obtain more information about the impact of small-scale events and
environmental changes on regional and global biota of the end-
Devonian, it is necessary to examine ecospace occupation of in-
vertebrates as well as vertebrates in other localities during this time
interval.
Acknowledgments
We thank the Swiss National Fond for supporting this project (S-
74602-11-01) and the NWO, VIDI 864.14.009 to support the colla-
boration of Martin Rücklin. The Ministère de l'Energie, des Mines, de
l'Eau et de l'Environnement (Rabat, Morocco) kindly provided permis-
sions for fieldwork and sampling. We thank the excellent preparators
Christina Brühwiler (University of Zurich), Ben Pabst (Zürich) and
Claudine Misérez (Neuchâtel) for their careful work. Many thanks to
René Kindlimann (Aathal), Michael Coates (University of Chicago) and
Michał Ginter for the instructive discussions about Paleozoic and
modern chondrichthyans. We also would like to thank Michael Amler
(Köln) for the kind help with the determination of bivalves. We also
thank the reviewers (Sandra Kaiser, State Museum of Natural History of
Stuttgart; Thomas Becker, University of Münster) who helped to im-
prove this manuscript.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.palaeo.2017.12.028.
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Supplementary material
Table S1. Primary data of invertebrate associations found in the Famennian at Madène el
Mrakib.
Association
Source of data Stratigraphic age Number of all species; only ammonoids genera
Groups in trophic nucleus
Modes of life
A (Fig. 4A-B, 5A)
Newly collected at Madène el Mrakib, housed at PIM
-lower Famennian -Ammonoids: Ammonoidea indet. 1 → Cheiloceras horizon
3; 1 -Brachiopods (1 taxa)
- Pelagic, slow-motile, predator - Surficial, non-motile attached,
suspension feeder
B (Fig. 4A-B, 5B)
Newly collected at Madène el Mrakib, housed at PIM
-lower Famennian -Ammonoids: Ch. (Staffites) afrispina → Cheiloceras horizone
4; 1 -Ammonoids (1 taxa) -Brachiopods (1 taxa)
-Pelagic, slow-motile, predator -Surficial, non-motile attached, suspension feeder -Semi-infaunal or surficial, non-motile, unattached, suspension feeder
C (Fig. 4A-B, 5C)
Newly collected at Madène el Mrakib, housed at PIM
-lower Famennian -Ammonoids: Ch. (Staffites) afrispina Armatites beatus Aulatornoceras sp. Torleyoceras sp. Falcitornoceras bilobatum falciculum → Cheiloceras horizon
12; 5 -Ammonoids (3 taxa) -Orthocerids (1 taxa)
-Pelagic, slow-motile, predator -Surficial, non-motile attached, suspension feeder -Benthic, no further details known
D (Fig. 4A-B, 5D)
Newly collected at Madène el Mrakib, housed at PIM
-middle Famennian -Ammonoids : Tornoceratidae → horizon ?
5; 2 -Orthocerids (1 taxa)
-Pelagic, slow-motile, predator -Surficial, non-motile attached, suspension feeder -Semi-infaunal or surficial, non-motile, unattached, suspension feeder
E (Fig. 4A-B, 5E)
Newly collected at Madène el Mrakib, housed at PIM
-middle Famennian -Ammonoids: Maeneceras acutolaterale → Maeneceras horizon
8; 2 -Phyllocarids (1 taxa)
-Pelagic, fast-motile, deposit feeder -Pelagic, slow-motile, predator -Surficial, facultatively motile, unattached, suspension feeder -Semi-infaunal or surficial, non-motile, unattached, suspension feeder -Benthic, no further details known
F (Fig. 4A-B, 5F)
Newly collected at Madène el Mrakib, housed at PIM
-middle Famennian -Ammonoids : Sporadoceras sp. → horizon?
11; 1 -Brachiopods (1 taxa) -Bivalves (1 taxa) -Orthocerids (1 taxa)
-Pelagic, slow-motile, predator -Erected, non-motile attached, suspension feeder -Surficial, facultatively motile, attached, suspension feeder -Surficial, non-motile attached, suspension feeder -Semi-infaunal or surficial, non-motile, unattached, suspension feeder -Shallow infaunal, facultatively motile, unattached, suspension feeder -Benthic, no further details known
G (Fig. 4A-B, 5G)
Newly collected at Madène el Mrakib, housed at PIM
-middle Famennian -Ammonoids : Planitornoceras pugnax Erfoudites sp. → Planitornoceras horizon
9; 2 -Ammonoids (1 taxa) -Orthocerids (1 taxa)
-Pelagic, slow-motile, predator -Surficial, slow-motile, grazer -Surficial, facultatively motile, unattached, suspension feeder -Surficial, non-motile attached, suspension feeder -Semi-infaunal or surficial, non-motle, unattached, suspension feeder -Benthic, no further details known
47
Chapter I: Alpha Diversity and Palaeoecology
Association
Source of data Stratigraphic age Number of all species; only ammonoids genera
Groups in trophic nucleus
Modes of life
H (Fig. 4A-B, 5H)
Newly collected at Madène el Mrakib, housed at PIM
-middle Famennian -Ammonoids: Planitornoceras pugnax Erfoudites spiriferus Pseudoclymenia sp. → Planitornoceras horizon
14; 4
-Ammonoids (1 taxa) -Orthocerids (1 taxa) -Brachiopods (2 taxa)
-Pelagic, slow-motile, predator -Surficial, non-motile attached, predator -Surficial, non-motile attached, suspension feeder -Semi-infaunal or surficial, facultatively motile, unattached, suspension feeder -Semi-infaunal, non-motile, unattached, suspension feeder -Shallow infaunal, facultatively motile, unattached, suspension feeder
I (Fig. 4A-B, 5I)
Newly collected at Madène el Mrakib, housed at PIM
-Upper Famennian (Annulata Black Shales) -Ammonoids : Platyclymenia annulata → Platyclymenia horizon
2; 1
-Ammonoids (1 taxa)
-Pelagic, slow-motile, predator
J (Fig. 7, Table S3)
Madène el Mrakib, partially published in Korn et al. (2014, 2015a) housed at MNB
-Upper Famennian
-Ammonoids: → Platyclymenia horizon
NA; 5
-Ammonoids (2 taxa)
-Pelagic, slow-motile, predator
K (Fig. 4A-B, 5J)
Newly collected at Madène el Mrakib, housed at PIM
-Upper Famennian -Ammonoids : Playtclymenia sp. Prionoceras lamellosum and lentis Cyrtoclymenia sp. Procymaclymenia ebbighauseni Erfoudites rherisensis Sporadocers cf. muensteri → Platyclymenia/ Procymaclymenia horizon
22; 6 -Ammonoids (7 taxa) -Orthocerids (1 taxa)
-Pelagic, slow-motile, predator -Surficial, slow-motile, grazer -Surficial, facultatively motile, unattached, suspension feeder -Surficial, non-motile attached, suspension feeder -Semi-infaunal or surficial, non-motile, unattached, suspension feeder -Shallow infaunal, facultatively motile, unattached, suspension feeder
L (Fig. 7, Table S3)
Madène el Mrakib, partially published in Korn et al. (2014, 2015a), housed at MNB
-Upper Famennian - Ammonoids: → Platyclymenia/ Procymaclymenia horizon
NA; 7 -Ammonoids (5 taxa)
-Pelagic, slow-motile, predator
M (Fig. 7, Table S3)
Madène el Mrakib, partially published in Korn et al. (2014, 2015a), housed at MNB
-Upper Famennian -Ammonoids: →Platyclymenia/ Procymaclymenia horizon
NA; 7 -Ammonoids (4 taxa)
-Pelagic, slow-motile, predator
N (Fig. 7, Table S3)
Madène el Mrakib, partially published in Korn et al. 2014, 2015a), housed at MNB
-Uppermost Famennian -Ammonoids : → Gonioclymenia horizon
NA; 7 -Ammonoids (7 taxa)
-Pelagic, slow-motile, predator
O (Fig. 7. Table S3)
Madène el Mrakib, partially published in Korn et al. (2014, 2015a), housed at MNB
-Uppermost Famennian -Ammonoids: → Kalloclymenia to Wocklumeria horizon
NA; 1 -Ammonoids (6 taxa)
-Pelagic, slow-motile, predator
P (Fig. 4A-B, 5K)
Newly collected at Madène el Mrakib, housed at PIM
-Uppermost Famennian -Ammonoids: → Wocklumeria horizon
7; 1? -Ammonoids (1 taxa) -Orthocerids (1 taxa) -Trilobites (1 taxa)
-Pelagic, slow-motile, predator -Surficial, fast-motile, suspension feeder/predators -Surficial, slow-motile -Surficial, non-motile attached, suspension feeder
Q (Fig. 4A-B, 5L)
Newly collected at Madène el Mrakib, housed at PIM
-Uppermost Famennian (Hangenberg Black Shales); -Ammonoids: Postclymenia calceola Mimimitoceras sp. Acutimitoceras sp. Tornoceratoidea → Postclymenia horizon
11; 4
-Bivalves (1 taxa) - Cephalopods (2 taxa)
-Pelagic, slow-motile, predator -Surficial, non-motile attached, suspension feeder
48
Chapter I: Alpha Diversity and Palaeoecology
Table S2. Primary data of invertebrate associations found in the Tournaisian at Aguelmous
(according to Ebbighausen and Bockwinkel, 2007).
Association
Source of data Stratigraphic age Number of all species; only ammonoids genera
Groups in the trophic nucleus
Modes of life
R (Fig. 6A) Aguelmous, Bed 2 in Ebbighausen and Bockwinkel (2007), housed at MNB
-Lower Tournaisian -Ammonoids: Acutimitoceras intermedium Acutimitoceras sarahae Acutimitoceras endoserpens Acutimitoceras algeriense Acutimitoceras posterum Acutimitoceras pentaconstrictum Acutimitoceras hollardi Acutimitoceras depressum Acutimitoceras occidentale Acutimitoceras mfisense Costimitoceras aitouamar Imitoceras oxydentale Weyerella sp. Eocanites simplex Kazakhstania nitida Kazakhstania evoluta Kornia citrus Gattendorfia jacquelinae → Gattendorfia/ Kahlacanites horizon
32; 8 -Ammonoids (4 taxa) -Gastropods (1 taxa)
-Pelagic, slow-motile, predator -Surficial, slow-motile, grazer -Surficial, non-motile attached, predator -Surficial, non-motile attached, suspension feeder -Benthic, no further details known
S (Fig. 6B) Aguelmous, Bed 12 in Ebbighausen and Bockwinkel (2007), housed at MNB
-Lower Tournaisian -Ammonoids: Acutimitoceras algeriense Gattendorfia ihceni Gattendorfia jacquelina → Gattendorfia/ Kahlacanites horizon
8; 2 -Ammonoids (3 taxa)
-Pelagic, slow-motile, predator -Surficial, slow-motile, grazer -Benthic, no further details known
T (Fig. 6C) Aguelmous, Bed 16 in Ebbighausen and Bockwinkel (2007), housed at MNB
-Lower Tournaisian -Ammonoids: Kahlacanites mariae Kahlacanites meyendorffi Gattendorfia debouaaensis Gattendorfia gisae Gattendorfia jacquelinae Hasselbachia arca Hassdelbachia gourara Acutimitoceras algeriense Eocanites sp. Becanites sp. → Gattendorfia/ Kahlacanites horizon
15; 6 -Ammonoids (6 taxa)
-Pelagic, slow-motile, predator
U (Fig. 6D) Aguelmous, Bed 18 in Ebbighausen and Bockwinkel (2007), housed at MNB
-middle Tournaisian -Ammonoids: Acutimitoceras sp. Protocanites hollardi Globimitoceras rharrizense Imitoceras sp. Gattendorfia sp. Goniocyclus elatrous Eocanites → Goniocyclus horizon
9; 7 -Ammonoids (4 taxa)
-Pelagic, slow-motile, predator
49
Chapter I: Alpha Diversity and Palaeoecology
Figure S1. Relative abundances of species occurring in the Maïder region (Morocco); red
bars represent the dominant species of the association. Diversity corresponding with the
Wocklumeria Stage of Madène el Mrakib, 7 taxa (excluding crinoids and bioturbation) are
depicted.
Figure S2. Rarefaction tests of Famennian and Tournaisian associations including all
invertebrate groups; blue lines represent confidential intervals; red lines show how many taxa
would have been theoretically sampled with further collection of specimens; green line: how
many taxa would have been theoretically sampled within 90 specimens.
50
Chapter I: Alpha Diversity and Palaeoecology
51
Chapter I: Alpha Diversity and Palaeoecology
Figure S3. Rarefaction tests of Famennian and Tournaisian ammonoid associations
containing at least three taxa; blue lines represent confidential intervals; red lines show how
many taxa would have been theoretically sampled with further collection of specimens.
52
Chapter I: Alpha Diversity and Palaeoecology
53
Chapter I: Alpha Diversity and Palaeoecology
Tab
le S3. R
aw data of F
amennian invertebrate sam
ples collected at Madène el M
rakib (northeastern Anti-A
tlas, Morocco).
Class
Species
Mode of life
Association A
Association B
Association C
Association D
Association E
Association F
Association G
Association H
Association I
Association J
Association K
Association L
Association M
Association N
Association O
Association P
Association Q
Association R
Association S
Association T
Association U
Cephalo
poda
Orth
oce
rida in
det. 1
p, fs
, pr
3
47
38
86
14
15
67
31
2
19
3
Orth
oce
rida in
det. 2
p, fs
, pr
1
Orth
oce
rida in
det. 3
(Murc
his
onic
era
s)
p, fs
, pr
2
Orth
occe
rida in
det. 4
p, fs
, pr
49
14
9
Orth
oce
rida in
det. 5
p, fs
, pr
4
Orth
oce
rida in
det. 6
p, fs
, pr
3
Spyro
cera
s s
p.
p, fs
, pr
3
Ba
ctritid
ae
ind
et.
p, fs
, pr
1
2
1
Am
monoid
ea in
det. 1
p, fs
, pr
2
Am
monoid
ea in
det. 2
p, fs
, pr
3
Am
monoid
ea in
det. 3
p, fs
, pr
2
Am
monoid
ea in
det. 4
p, fs
, pr
1
Am
monoid
ea in
det. 5
p, fs
, pr
7
Am
monoid
ea in
det. 6
p, fs
, pr
Torn
ocera
toid
ea
p, fs
, pr
1
5
Falc
itorn
ocera
s fa
lcic
ulu
m
p, fs
, pr
2
Falc
itorn
ocera
s b
ilobatu
m
p, fs
, pr
6
Au
lato
rno
cera
s s
p.
p, fs
, pr
16
Pla
nito
rnocera
s p
ugnax
p, fs
, pr
231
36
Arm
atite
s b
eatu
s
p, fs
, pr
21
54
Chapter I: Alpha Diversity and Palaeoecology
Pse
ud
ocly
me
nia
sp.
p, fs
, pr
1
Pro
cym
acly
menia
ebbig
hauseni
p, fs
, pr
6
Torle
yocera
s s
p.
p, fs
, pr
1
Ch. (S
taffite
s) a
frispin
a
p, fs
, pr
160
56
Mae
ne
ce
ras a
cu
tola
tera
le
p, fs
, pr
1
Spora
docera
s s
p.
p, fs
, pr
1
Sp
ora
doce
ras m
uenste
ri p, fs
, pr
1
58
Sp
ora
doce
ras g
lobu
losu
m
p, fs
, pr
11
Spora
docera
s c
onfo
rme
p, fs
, pr
1
Erfo
ud
ites rh
eris
ensis
p, fs
, pr
2
210
10
Erfo
ud
ites s
pirife
rus
p, fs
, pr
2
Erfo
ud
ites s
p.
p, fs
, pr
1
Prio
nocera
s le
ntis
p, fs
, pr
356
37
Prio
nocera
s la
mello
sum
p, fs
, pr
1752
17
Prio
nocera
s v
etu
s
p, fs
, pr
34
Prio
nocera
s ta
khbtite
nse
p, fs
, pr
16
Prio
nocera
s m
rakib
ense
p, fs
, pr
138
Prio
nocera
s o
uaro
uro
ute
nse
p, fs
, pr
61
Prio
nocera
s s
ubtu
m
p, fs
, pr
3
Pro
tacto
cly
me
nia
sp. 2
p, fs
, pr
1
3
Pro
tacto
cly
me
nia
di
p, fs
, pr
10
Pro
tacto
cly
me
nia
du
p, fs
, pr
3
11
Cyrto
cly
menia
sp. 1
p, fs
, pr
6
Pla
tycly
me
nia
an
nula
ta
p, fs
, pr
100
Pla
tycly
me
nia
sp
. 2
p, fs
, pr
74
38
Pla
tycly
me
nia
sp
. p, fs
, pr
6
Pla
tycly
me
nia
ibnsin
ai
p, fs
, pr
5
Pla
tycly
me
nia
xxP
ls
p, fs
, pr
30
55
Chapter I: Alpha Diversity and Palaeoecology
Pla
tycly
me
nia
xxP
li p, fs
, pr
23
49
Pla
tycly
me
nia
xxP
lv
p, fs
, pr
4
Pla
tycly
me
nia
xxP
lg
p, fs
, pr
6
8
Pla
tycly
me
nia
a-i
p, fs
, pr
28
4
Pla
tycly
me
nia
inv
p, fs
, pr
24
31
Pla
tycly
me
nia
evo
p, fs
, pr
6
Pla
tycly
me
nia
um
b
p, fs
, pr
3
Po
stc
lym
en
ia c
alc
eo
la
p, fs
, pr
33
Cym
acly
en
ia s
ub
vexa
p, fs
, pr
79
Cym
acly
en
ia fo
rmosa
p, fs
, pr
16
Cym
acly
en
ia la
mb
idia
p, fs
, pr
15
Cym
acly
en
ia c
arn
ata
p, fs
, pr
1
Mim
imito
cera
s s
p.
p, fs
, pr
22
Mim
imito
cera
s c
arn
atu
m
p, fs
, pr
78
Mim
imito
cera
s c
om
tum
p, fs
, pr
59
Acutim
itoce
ras s
p. 3
p, fs
, pr
2
Acutim
itoce
ras s
p. 4
p, fs
, pr
1084
73
17
83
Acutim
itoce
ras s
p. A
p, fs
, pr
19
Acutim
itoce
ras h
olla
rdi
p, fs
, pr
18
Acutim
itoce
ras in
term
ed
ium
p, fs
, pr
292
Acutim
itoce
ras o
ccid
en
tale
p, fs
, pr
43
Acutim
itocera
s d
epre
ssum
p, fs
, pr
16
Acutim
itoce
ras s
ara
ha
e
p, fs
, pr
171
Acutim
itoce
ras m
fise
nse
p, fs
, pr
9
Acutim
itoce
ras e
ndose
rpe
ns
p, fs
, pr
119
Acutim
itoce
ras a
lgerie
nse
p, fs
, pr
1
17
5
Acutim
itocera
s p
oste
rum
p, fs
, pr
1
Acutim
itoce
ras p
enta
constric
tum
p, fs
, pr
1
56
Chapter I: Alpha Diversity and Palaeoecology
lmito
cera
s o
xydenta
le
p, fs
, pr
32
lmito
cera
s s
p.
p, fs
, pr
21
Gatte
ndorfia
jacquelin
ae
p, fs
, pr
5
2
9
Gatte
ndorfia
debouaaensis
p, fs
, pr
35
Gatte
ndorfia
lhceni
p, fs
, pr
28
Gatte
ndorfia
gis
ae
p, fs
, pr
21
Ga
tten
do
rfia s
p. 1
p, fs
, pr
10
Ga
tten
do
rfia s
p. 2
p, fs
, pr
18
21
Eo
ca
nite
s s
imp
lex
p, fs
, pr
14
Eo
ca
nite
s s
p. 1
p, fs
, pr
2
Eo
ca
nite
s s
p. 2
p, fs
, pr
1
3
1
Glo
bim
itoce
ras rh
arrh
izen
se
p, fs
, pr
32
Costim
itocera
s a
itouam
ar
p, fs
, pr
49
Ha
sse
lba
chia
gou
rara
p, fs
, pr
2
Ha
sse
lba
chia
arc
a
p, fs
, pr
25
Hasselb
achia
sp.
p, fs
, pr
3
Ko
rnia
citru
s
p, fs
, pr
7
Ka
zakh
sta
nia
evo
luta
p, fs
, pr
5
Ka
zakh
sta
nia
nitid
a
p, fs
, pr
13
Go
nio
cyclu
s e
latro
us
p, fs
, pr
9
Be
ca
nite
s s
p.
p, fs
, pr
1
Ka
hla
can
ites m
aria
e
p, fs
, pr
52
Ka
hla
can
ites m
eyen
do
rffi p, fs
, pr
1
Ka
hla
can
ites s
p.
p, fs
, pr
55
Pro
toca
nite
s h
olla
rdi
p, fs
, pr
64
Weyere
lla s
p.
p, fs
, pr
24
Trig
onocly
menia
sp.
p, fs
, pr
5
Pro
toxycly
me
nia
we
nd
ti p, fs
, pr
9
Nanocly
menia
sp.
p, fs
, pr
10
57
Chapter I: Alpha Diversity and Palaeoecology
Pro
cym
acly
menia
ebbig
hauseni
p, fs
, pr
98
Unguspora
docera
s u
nguifo
rme
p, fs
, pr
8
Gundolfic
era
s v
escum
p, fs
, pr
3
Po
stto
rno
cera
s e
ega
ntu
m
p, fs
, pr
3
Alp
inite
s s
ch
ultze
i p, fs
, pr
1
Ebbig
hausenite
s w
eyeri
p, fs
, pr
1
Dis
cocly
me
nia
atla
nte
a
p, fs
, pr
2
Alp
inite
s zig
zag
p, fs
, pr
1
Gonio
cly
menia
wendti
p, fs
, pr
17
Gonio
cly
menia
ali
p, fs
, pr
10
Gonio
cly
menia
spin
iger
p, fs
, pr
1
Kosm
ocly
meniid
ae in
det.
p, fs
, pr
26
Kosm
ocly
menia
sp.
p, fs
, pr
1
Biv
alv
ia
Biv
alv
ia in
det. 1
benth
ic
1
Biv
alv
ia in
det. 2
benth
ic
2
Biv
alv
ia in
det. 3
benth
ic
1
Biv
alv
ia in
det. 4
benth
ic
1
2
Biv
alv
ia in
det. 5
benth
ic
1
Biv
alv
ia in
det. 6
benth
ic
1
Biv
alv
ia in
det. 7
benth
ic
2
Biv
alv
ia in
det.8
benth
ic
1
Biv
alv
ia in
det. 9
benth
ic
3
Biv
alv
ia in
de
t. 11 (n
ucu
lid)
benth
ic
6
Biv
alv
ia in
det. 1
2
benth
ic
1
Biv
alv
ia in
det. 1
0
benth
ic
3
Biv
alv
ia in
det. 1
3
benth
ic
1
Bu
ch
iola
(Bu
ch
iola
) sp.
sm
i/su,n
u, s
f 2
8
3
2
1
Gly
pto
ha
llica
rdia
sp.
sm
i/su, n
u, s
f 3
3
Gueric
hia
cf. v
enusta
su
, na, s
f 3
5
4
1
3
58
Chapter I: Alpha Diversity and Palaeoecology
Gueric
hia
ellip
tica
su
, na, s
f
280
Pro
soch
asm
a s
p.
su, fa
, sf
34
Op
isth
oco
elu
s s
p.
su, fa
, sf
1
1
?M
etro
ca
rdia
sp.
si, fu
, sf
3
Lo
xo
pte
ria s
p.
su, fu
, sf
1
?P
tych
opte
ria s
p.
su, fa
, sf
3
?S
treb
lop
teria
sp.
su, fa
, sf
3
Pala
eoneilo
sp
. si, fu
, df
2
3
Am
phig
astro
poda
Belle
rophon (A
gla
ogly
pta
) su
, fs, g
2
Belle
rophontid
ae in
det.
su
, fs, g
7
Gastro
poda
Gastro
poda in
det. 1
su
, fs, g
3
Gastro
poda in
det. 2
su
, fs, g
2
6
Gastro
poda in
det. 3
su
, fs, g
60
Gastro
poda in
det. 4
su
, fs, g
9
Gastro
poda in
det. 5
su
, fs, g
58
Gastro
poda in
det. 6
su
, fs, g
2
Gastro
poda in
det. 7
su
, fs, g
1
Macro
ch
ilina s
p.
su
, fs, g
1
Rhynchonella
ta
Rhynchonella
ta in
det. 1
su
, na, s
f 1700
Rhynchonella
ta in
det. 2
su
, na, s
f 122
1
Rhynchonella
ta in
det. 3
su
, na, s
f 5
39
12
3
4
Rhynchonella
ta in
det. 4
su
, na, s
f 3
3
Rhynchonella
ta in
det. 5
4
Phacoid
erh
ynchus a
ntia
tlasic
us
su
, na, s
f 4
Au
lace
lla s
p.
su
, na, s
f 1
Sp
iriferid
a
Spirife
rida in
det.
su
, na, s
f
1
Lin
gula
ta
Lin
gula
ta in
det.
si, n
a, s
f 3
Bra
ch
iop
od
a
Bra
ch
iop
od
a in
det. 1
13
59
Chapter I: Alpha Diversity and Palaeoecology
Ph
yllo
ca
rida
Ph
yllo
ca
rida
inde
t p, ff, d
f 151
Trilo
bita
T
rilobita
indet.
su
, ff, pr/d
f 7
Crin
oid
ea
Crin
oid
ea in
det.
er, n
a, s
f 1
Tabula
ta
Tabula
ta in
det.
su
, na, s
f
1
Rugosa
Rugosa in
det. 1
su
, na, p
r 2
Rugosa in
det. 2
su
, na, p
r
6
Rugosa in
det. 3
su
, na, p
r 1
Bry
ozo
a
Bry
ozo
a in
det
su
, na, s
f 5
CHAPTER II
Fossil-Lagerstätten and preservation of invertebrates and vertebrates from the Devonian in the eastern Anti-Atlas
(Morocco)
Linda Frey, Alexander Pohle, Martin Rücklin and Christian Klug
Submitted to : Lethaia
63
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Fossil-Lagerstätten and preservation of invertebrates and vertebrates from the Devonian in the eastern Anti-Atlas (Morocco)
LINDA FREY, ALEXANDER POHLE, MARTIN RÜCKLIN and CHRISTIAN KLUG
Frey, L., Pohle, A., Rücklin, M. & Klug, C. 20XX. Fossil-Lagerstätten and preservation of vertebrates and invertebrates from the Moroccan Devonian (eastern Anti-Atlas). Lethaia.
Throughout the Devonian, fossil invertebrates are abundant in the eastern Anti-Atlas and depending on the strata, they display a high taxonomic diversity. Fossils of jawed vertebrates have been recorded after the early Lochkovian so far and are relatively common with their abundance and diversity increasing towards the Late Devonian. Fossil preservation varies strongly, partially refl ecting the disintegration of the continental shelf of Gondwana in this region in three epicontinental basins and pelagic ridges during the Devonian and fl uctuations of the regional sea-level. We analyzed the mineral composition of several invertebrate and vertebrate samples of Devonian and Early Carboniferous age by Raman spectroscopy and X-ray diffraction. We use the results of these analyses combined with palaeogeographic and palaeoecological data to interpret the genesis of Devonian Fossil-Lagerstätten of this region. Accordingly, we list eight examples of the numerous Devonian Konzentrat-Lagerstätten and two examples of Konservat-Lagerstätten with soft-tissue preservation (the Famennian Thylacocephalan Layer and the Hangenberg Black Shale of the southern Maïder). The latter are the fi rst two of this kind of Fossil-Lagerstätte from the Devonian of North Africa. The taphonomic and oceanic settings suggest that these Konservat-Lagerstätten formed due to stagnation (perhaps related to vertical restriction of water exchange and water depth rather than limited spatial water exchange and a lateral restriction) in the relatively small Maïder Basin with limited water exchange with the neighboring Tafi lalt Basin. The poor lateral or vertical water exchange could also explain the reduced chondrichthyan diversity compared to the Tafi lalt Platform, where the water was shallower and probably better oxygenated at depth. □ Exceptional preservation, Raman-spectroscopy, X-ray Diffraction, mineralogy, weathering, Chondrichthyes, Placodermi, Ammonoidea.
Linda Frey [[email protected]], Alexander Pohle [[email protected]], Christian Klug [[email protected]], Paläontologisches Institut und Museum, University of Zurich, Karl Schmid-Strasse 4, CH-8006 Zürich, Switzerland; Martin Rücklin [[email protected]], Naturalis Biodiversity Center, Postbus 9517, NL-2300 RA Leiden, the Netherlands.
Two fi elds of research concerning the palaeontology of the Devonian in Morocco have been explored only rarely yet: Fossil-Lagerstätten and taphonomy. The term Fossil-Lagerstätten (Seilacher 1970) applies to deposits where fossils occur either in a very high abundance or in exceptional preservation including soft tissues and articulated skeletons; both cases occur in the eastern Anti-Atlas as we demonstrate here, although the former kind is much more common than the latter. Therefore, we put a special emphasis on two poorly documented Famennian cases of the latter kind (Konservat-Lagerstätten). In order to understand the formation of Fossil-Lagerstätten, we follow three approaches: it is essential to examine and understand the taphonomic processes that are involved (approach 1), the palaeogeographic setting (approach 2) and the palaeo-environmental conditions (approach 3).
Taphonomic processes (approach 1) can partially be reconstructed using information from the mode of preservation and also the mineralogy
of the fossils under consideration. Based on the colour, host sediments and surface patterns, preservation in a series of different minerals is inferred for vertebrate and invertebrate fossils from the arid eastern Anti-Atlas (Fig. 1). Although their actual mineralogical composition was rarely tested (e.g., Klug et al. 2009, 2016), the mineralogy of the respective fossil is inferred commonly based rather on speculation than actual mineralogical examinations (e.g., Pohle & Klug 2018). Consequently, the analysis of the mineral composition of fossils of various ages and localities from the Devonian of the Anti-Atlas is crucial. Here, we discuss possible implications of fossil preservation for palaeoenvironment reconstruction and interpretations of the taphonomy and consider possible secondary alteration due to weathering. Based on taphonomic, palaeogeographic and facies data, palaeoenvironment and palaeoecology are reconstructed and the infl uence on the vertebrate diversity is analysed.
The study of taphonomy is of interest because only in the Maïder Basin, chondrichthyans
64
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
preserving cartilaginous body parts as well as soft tissues have been discovered. Hence, the new data on preservation will shed light on how the Konservat-Lagerstätten of the Maïder region formed (Klug et al. 2016; Frey et al. 2018).
The second approach to understand the formation of Fossil-Lagerstätten is the study of the palaeogeographic setting and facies. Fortunately, the arid climate keeps vegetation to a minimum in the Moroccan pre-Sahara, thus creating formidable outcrops. Therefore, facies changes can be examined in space and through geologic time in order to reconstruct the arrangement of basins and carbonate ramps with ridge and swell topography, and the approximate situation of coastlines throughout the Devonian (e.g., Hollard 1974; Wendt 1985, 1988; Wendt and Belka 1991; Kaufmann 1998; Döring and Kazmierczak 2001; Lubeseder et al. 2010). Since the required palaeogeographic data are readily available from
the literature, we do not add new details to this aspect, but provide a brief review necessary for the interpretation of the Lagerstätten type.
In our third approach, we qualitatively assess the palaeo-environment and palaeoecology through the Devonian of the eastern Anti-Atlas. Devonian sedimentary sequences of this region contain numerous different facies types and thus also various kinds of sediments with a broad range of vertebrate, invertebrate and plant fossils (e.g., Clariond 1936; Termier and Termier 1950; Lehman 1956, 1964, 1976, 1977; Lelièvre and Janvier 1986, 1988; Belka et al. 1999; Derycke 1992; Becker et al. 2000; Rücklin 2010, 2011; Frey et al. 2014; Rücklin et al. 2015; Korn et al. 2016a, b; Rücklin and Clément 2017). In the Famennian of the eastern Anti-Atlas, fossil invertebrates but also vertebrates can be found in sometimes impressive numbers. As far as vertebrates are concerned, microremains of gnathostomes are quite common
Fig. 1. Geologic map of the eastern Anti-Atlas of the Maïder and Tafi lalt Basins as well as the Tafi lalt Platform. Only some examples of vertebrate occurrences of the Famennian are given: arthodire remains can be found in almost every larger outcrop of the Famennian in this region.
65
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
in some strata (Derycke 1992; Ginter et al. 2002; Derycke et al. 2008) due to condensed sedimentation, particularly in the Tafi lalt. In the latter region, chondrichthyan diversity can be reasonably high (up to nine species in one layer). By contrast, in the Famennian of the southern Maïder Basin, chondrichthyan diversity appears to be lower (four to fi ve species) and some genera have not been found there yet although they are documented from the neighbouring Tafi lalt Basin (Ginter et al. 2002; Derycke et al. 2008).
Invertebrates, however, can usually deliver more detailed information on palaeoecology, partially because they often occur in statistically relevant numbers to carry out quantitative analyses. Several groups of invertebrates are very common in Devonian strata of the eastern Anti-Atlas. It is thus not surprising that some of the carbonate build-ups contain abundant corals (e.g., Kaufmann 1998; Berkowski 2006) and brachiopods (Halamski and Baliński 2013; Tessitore et al. 2013). Similarly, ammonoids are common from the Emsian to the Visean (e.g., Klug 2001; De Baets et al. 2013; Korn et al. 2007, 2016a, b) and occur in an impressive diversity, but their modes of preservation are almost as diverse. Other groups such as trilobites, crinoids, bivalves etc. occur as well, sometimes in vast numbers, but these were examined only in the palaeoecological context and not for their preservation. In this approach, we also rely on published data, which are briefl y summarized.
In this article, we address the following questions: (1) What is the mineral composition of invertebrate and vertebrate fossils in the Devonian of the eastern Anti-Atlas? (2) Is this composition primary or altered by taphonomic or weathering processes? (3) What can we deduce from the palaeogeographic setting for the formation of Fossil-Lagerstätten? (4) What are the implications derived from the preservational mode for the palaeoenvironment and the according differences in faunal composition? (5) What kinds of Fossil-Lagerstätten occur in the Anti-Atlas?
Material and methods
Material
All specimens (except one) were collected by the authors in the eastern Anti-Atlas. We chose the samples with the intention to include a broad range of different preservations in order to cover the main minerals occurring in fossils of the eastern Anti-Atlas. Most of these specimens are kept at the Paläontologisches Institut und Museum of the University of Zurich with numbers with the abbreviation PIMUZ. Some specimens are
stored at the Institut für Geowissenschften at the University of Tübingen with the abbreviation GPIT.
Mineral analyses
We analysed 30 samples (Tab. 1, 2) taken from invertebrates and vertebrates of mostly Devonian age (two from the Early Carboniferous) from the Maïder and the Tafi lalt (eastern Anti-Atlas). Table 1 and 2 show details and the mineral composition. Fossil preservation was examined by analysing their mineral composition using Raman spectroscopy and XRD (X-ray Diffraction) at the Swiss Federal Institute of Technology in Zurich (ETHZ).
Raman spectroscopy was performed with a DILOR LabRam (with built-in Olympus BX 40 microscope); grating was 600 or 1800 grooves/ mm, CCD sensor resolution 1152*298 pixels spectral resolution 1.3 – 1.5 cm-1 (for 1800 grating). Laser wavelength was 532.14 nm (with max. 500 mW laser power at the source) generated by a DPSS laser (Diode-pumped solid-state lasers). Measurements of laser Power were performed with a COHERENT LaserCheck hand-held device at 40% (Laser power: 195 mW at source, 19.7 mW with 100x, 26 mW with 50x on the sample). For the analyses of the spectra, we used the software CrystalSleuth (Laetsch & Downs 2006) and the American Mineralogist Crystal Structure Database (Downs & Hall-Wallace 2003). Some of the minerals rich in iron could not be measured properly, because the laser in use is red and too close in wavelength to that refl ected by these minerals.
For the XRD, we used a D8-advance (Bruker AXS) diffractometer in the Geochemistry and Petrology Laboratories of the ETHZ. All samples were crushed in an Agate bowl prior to analysis and the resulting fi ne powder was then prepared on sample holders. The diffractometer operated at 40 mA and 40 kV with Cu Kα radiation at room temperature (25°C). A scintillation counter with secondary monochromator was used to identify the minerals. The scans were performed as θ-2θ locked with a step size of 0.02° and step time of 1.0 s between 5°-90°2θ. In several cases of the minerals rich in iron, crystal-size was possibly too small to be well-analyzed by XRD, hence the often noisy signal seen in the analyses.
Comparison of Konservat-Lagerstätten
In order to better classify the Konservat-Lagerstätten of the Maïder (Thylacocephalan Layer, erroneously dubbed Phyllocarid Layer before, Hangenberg Black Shale), we used the questionnaire proposed by Seilacher et al.
66
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
(1985). This questionnaire represents a list of characteristics grouped into aspects of the sedimentary basin, stratigraphy, sedimentology, geochemistry (here, we excluded some characteristics because of missing data from most Konservat-Lagerstätten), taxonomic composition,
ecology, taphonomy, and diagenesis. We did not code (1) the setting, because all are marine, (2) the origin, because all are sedimentary, (3) the isotopy, because of missing data from many of the localities, (4) terrestrial organisms, because of the marine setting, and (5) articulation, because
Tab. 1. Results of Raman-analyses of various Devonian and Carboniferous fossils from the eastern Anti-Atlas.
Tab. 2. Results of XRD-analyses of various Devonian fossils from the eastern Anti-Atlas. Samples kept under the number PIMUZ 36879.
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
all localities yielded articulated specimens. We slightly reduced their list to 31 characters. The completed questionnaire for both Konservat-Lagerstätten of the eastern Anti-Atlas (Appendix 1) and for 19 well-known marine Konservat-Lagerstätten (Tab. 3) are added. Characters were coded as follows:Marine basin size: 0 ‒ ≤ 1 km2; 0.5 ‒ 1 to 10 km2; 1 ‒ ≥ 10 km2 Facies: 0 ‒ limestone; 1 ‒ clastics Palaeolatitude: 0 ‒ tropical; 1 ‒ moderateThickness: 0 ‒ ≥ 1 m; 0.5 ‒ 1 to 10 m; 1 ‒ ≤ 10 mDuration: 0 ‒ ≥ 1 Ma; 0.5 ‒ 1 to 10 Ma; 1 ‒ ≤ 10 MaSea-level: 0 ‒ ≥ 10 m; 0.5 ‒ 10 to 100 m; 1 ‒ ≤ 100 mSediment structures: 0 ‒ lamination; 1 ‒ ripple marksFauna: 0 ‒ invertebrates dominant; 1 ‒ vertebrates common;Pelagics (macrofossils): 0 ‒ mostly nekton; 1‒ mostly plankton.The following characters were coded as 0 when absent and as 1 when present:Pyrite in sediment; trace fossils; infauna; epibenthos; death marches; landing marks; soft tissue preservation; cuticles; roll marks; current alignment of fossils; aragonite preservation; pyrite internal moulds; concretions; deformation (compaction); carbonization; phosphatisation; pyritisation of tissues; tissues replaced by clay minerals; silicifi cation; obrution (tempestites or turbidites etc.); stagnation (phases of low oxygen); bacterial/ algal mats preserving fossils. The matrix was analysed in PAST (Hammer et al. 2001) by a Principal Component Analysis on the correlation matrix.
Mineralogy of fossil groups
All analyses are shown in Tab. 1 and 2. Correspondingly the method used for each analysis is indicated there. Therefore, no individual indication whether the mineral content was determined by XRD or Raman is given.
Invertebrates
In the Devonian limestones of the eastern Anti-Atlas, cephalopod remains usually occur as limestone internal moulds and occasionally shells are replaced with calcite. Near faults and the angular disconformity contact of the Cenomanian transgression, the fossils are often slightly dolomitized (Fig. 2L). Many clayey intervals yield internal moulds of cephalopods that are preserved in iron oxides and hydroxides (Fig. 2B, C, J). Their reddish colour made the determination
of the mineral content by Raman-spectroscopy impossible, but the XRD-analyses (Tab. 2) proved that particularly the black internal moulds of cephalopods are composed predominantly of goethite. More reddish specimens contain additionally haematite. These goethitic internal moulds sometimes contain remains of a pyritic core. This indicated already, that all these goethitic internal moulds derive from pyritic specimens (this is corroborated by pseudomorphoses of goethite after pyrite), where the iron of the pyrite was slowly oxidized in the course of the deep weathering of the clay sediments. Further corroboration of this scenario is provided by a specimen of Cymaclymenia (Fig. 2A), which was found in a depth of about ten meters in a well. Its pyritic composition was determined by Raman spectroscopy (Tab. 1).
The late Famennian of the Jebel El Mrakib, Jebel Krabis and Lambidia region (Aguelmous syncline; Becker et al. 2018) has stratigraphic intervals rich in Cymaclymenia (Klein & Korn 2014). Claystones, marls and thin nodular limestones characterized these intervals. These nodules and their fossil content usually carry a dessert varnish giving them a shiny surface. We analysed one specimen each from the Rich Chouiref and Jebel El Krabis, both of calcitic composition.
In the Visean concretion containing the ammonoid Entogonites (C10), quartz and calcite occur. Other Tournaisian and Visean goniatites collected in proximity of Erg Chebbi are comparable in their quartz and calcite composition (Tab. 1, 2). The inner whorls of the phragmocone of goniatites from the Visean of the southeastern Tafi lalt (Fig. 2I) and other faunas are preserved in baryte. This preservation is also known from roughly coeval strata of the Rhenish Massif (Germany: Korn 1988) and some Jurassic sites (Blum 1843; Wenk 1967).
The highly abundant thylacocephalans from the Famennian Thylacocephalan Layer of Madene El Mrakib (Fig. 3) have a hydroxypatite composition in the greyish to bluish remains of the carapace, while the sparitic fi lling of the carapace is calcitic. The surrounding concretions are occasionally greenish, where they consist of calcite. The reddish concretions are rich in haematite.
Vertebrates
Since actinopterygians and sarcopterygians play a subordinate role in the Famennian faunas of the eastern Anti-Atlas, we analysed the mineral content of remains of chondrichthyans and placoderms (Table 1, 2, Fig. 3, 4), both of which occur abundantly in some Late Devonian strata (Lehman 1956, 1964, 1976, 1977; Frey et al. 2018).
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
The vertebrate remains are usually contained in nodules of varying colours suggesting a carbonatic or iron-rich composition, respectively. Mineral analyses of greyish to greenish nodules contain calcite and perhaps siderite matching with presumed carbonatic composition (Tab. 1, 2). Several nodules with chondrichthyan or thylacocephalan remains share an orange, red to yellowish colour. Composed of calcite, haematite (causing the colour), and goethite (and possibly other hydroxides).
Hydroxyapatite is measured as expected in placoderm bones, chondrichthyan cartilage, teeth and in the thylacocephalan carapaces (Tab. 1, 2). The cartilaginous branchial arches of a small chondrichthyan are preserved in hydroxyapatite and calcite, while in the body, there is mainly calcite, perhaps combined with siderite and
subordinate haematite. Anterior to the pelvic girdle a pyrite nodule is preserved with the characteristic cubic crystals, surrounded by a crust of iron minerals (haematite, goethite).
Palaeogeography and facies
Palaeogeography
The palaeogeographical setting of the eastern Anti-Atlas was published in a series of articles (for more details, see Wendt 1985, 1988; Wendt and Belka 1991; Kaufmann 1998; Klug and Korn 2002). The interpretation of a homocline carbonate ramp in the Early Devonian that disintegrated and developed into three small epicontinental marine basins during the Middle Devonian in the eastern
Tab. 3. Characterization of marine Konservatlagerstätten based on the “questionnaire” of Seilacher et al. (1985). Character coding is explained in the material and methods chapter (where only 0 and 1 is coded, 0 means absence and 1 means presence).
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Anti-Atlas is widely accepted (Fig. 5). For the Late Devonian a nearly rectangular western basin, the so-called Maïder Basin is described. It has a width (E-W) of about 70 km in longitude and a length (N-S) of about 80 km in latitude. Hiatuses spanning the Devonian or more refl ect the approximate limits of the basin to the south and north. In the west, outcrops of Devonian sediments represent a strongly reduced thickness, thus documenting
the presence of the Maïder Platform. Eastern areas are covered and therefore lack outcrops of Devonian sediments. Further east series of E-W trending synclines with exposures of more or less strongly condensed carbonatic sediments in the Eifelian and Famennian. Wendt (1985, 1988) and Kaufmann (1998) suggested that these sediments were laid down in a continuously submerged area of reduced water depth, the Tafi lalt Platform.
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Probably, this palaeogeographic setting reduced the water exchange with the surrounding basins and the open ocean towards the north. Additionally, there are indications for a water depth exceeding 200 metres in the Maïder Basin: In the Givetian, a large reef mound formed on the southern slope of the basin (Kaufmann 1998). This mound was about 200 to 300 m high (Kaufmann 1998, Tessitore et al. 2016). It is unknown, how much sediment accumulated around the mound during the time of its growth, but it is well conceivable that the water depth was around 200 m, because indications for subaerial exposure are missing and the mound slopes appear rather steep today. With the cessation of mound growth, sea-level was rising, as suggested by the very thick overlying sequence of clayey sediments of late Givetian to middle Famennian age. Consequently, the water was possibly over 200, maybe 300 or even 400 metres deep in the depocentre (Tessitore et al. 2016). It is thus well conceivable that, during the Middle and Late Devonian, water exchange was low between the Tafi lalt Basin in the East and the very distant Tindouf Basin in the Southwest and the Maïder Basin, especially with the deeper parts of the Maïder Basin.
Facies
In the eastern Anti-Atlas, the Devonian succession starts with a thick sequence of clayey sediments, usually poor in fossils of benthic organisms and dark in colour. This suggests anoxic to hypoxic conditions during most of the Lochkovian (Belka et al. 1999; Dopieralska et al. 2006; Frey et al. 2014). Pragian sediments contain more carbonate and marls as well as marly limestones. Some of these layers contain rich benthonic as well as planktonic assemblages, indicating increased oxygen levels (Frey et al. 2014; Klug
et al. 2018). At the onset of the Emsian, nodular marls occur in the Tafi lalt, followed by fi ne claystones (weathering to a greenish scree) that yielded the largely haematitic Faunule 1 (Klug et al. 2008). During a short regression, the Deiroceras Limestone (Kröger 2008) was laid down; these carbonates commonly form a 50 to 100 cm thick limestone bed that can be easily recognized in the Tafi lalt. This dacryoconarid wackestone to packstone contains abundant large nautiloids of the genus Deiroceras, hence the name (see also Pohle and Klug 2018). Above, claystones follow that contain the predominantly haematitic Faunule 2 (Klug et al. 2008; De Baets et al. 2010); this sedimentary unit was dubbed Metabactrites-Erbenoceras Shale by Becker and Aboussalam (2011; see also Aboussalam et al. 2015). The Erbenoceras Limestone (Klug 2001; = Anetoceras Limestone of Bultynck and Walliser 2000; see also De Baets et al. 2010) varies in thickness and facies. In the northern Maïder, the Erbenoceras Limestone consists of an over 40 m thick sequence of moderately thin-bedded mudstones and wackestones (Döring 2002). At Jebel Mdouar (= Gara Mdouara, Klug 2017), the Erbenoceras Limestone (Units D and E of Klug 2001) is only 5 m thick and three fossiliferous massive limestone beds (mostly dacryoconarid packstones, sometimes with great amounts of crinoids; Klug 2001), each about one meter thick, dominate the sequence. The Daleje Shales were laid down during a global transgression (Haq and Schutter 2008); their carbonate content is usually low and thickness varies between over 160 m southeast of Tazoulait in the Maïder Basin and less than 40 m at the northern and southern limits of the basin (Döring 2002).
Both thickness and facies variation increase throughout the Devonian (Hollard 1974; Wendt 1985; Kaufmann 1998; Döring and Kazmierczak
↑ Fig. 2. Ammonoids from the eastern Anti-Atlas in different modes of preservation. Scale bar (1 cm) applies to all materials except H (ruler with millimetre scale at the bottom right). A to G, Cymaclymenia spp., Famennian, Maïder. A, PIMUZ 36863, pyritic internal mould, found in a depth of ca. 10 m in a well near Tafraoute (analysis in Tab. 1, Fig. 4). B, C, PIMUZ 36864 and PIMUZ 36865, surface collected specimens, pyrite entirely replaced by goethite with some iron hydroxides. D, PIMUZ 36866, calcium carbonatic internal mould with collapsed body chamber; Lambidia. E, PIMUZ 36867, calcium carbonatic specimen with replacement shell (also calcite) showing growth lines, Lambidia. F, PIMUZ 36868, calcium carbonatic internal mould with dessert varnish, Chouiref (analysis in Tab. 1, Fig. 4). G, PIMUZ 36869, calcium carbonatic internal mould with growth lines on replacement shell and collapsed phragmocone. H, Postclymenia evoluta, PIMUZ 31561, Hangenberg Black Shale, Madene El Mrakib; fl attened internal mould preserving fi ne shell structures (wrinkle layer, sutures, growth lines) and carbonatic remains of the formerly chitinous lower jaw (also fi gured in Klug et al. 2016, fi g. 3I). I, Neogoniatites delicatus, GPIT 1851-101, Viséan-Namurian boundary, E of Taouz; baritic internal mould of the phragmocone. J, typical surface-collected Famennian ammonoids, mostly goethitic internal moulds, Filon Douze. K, Gonioclymenia cf. inornata, PIMUZ 36870, Famennian, Madene El Mrakib; external mould of the umbilicus with collapsed replacement shell and internal mould of the thick dorsal siphuncle. L, Sobolewia nuciformis, GPIT 1871-245, Eifelian, Richt Tamirant; dolomitized internal mould (also fi gured in Klug 2002, pl. 13, fi g. 5). M, Ponticeras kayseri, GPIT 1849-388, late Givetian, Ouidane Chebbi (also fi gured in Belka et al. 1999, pl. 4, fi g. 12); chambers fi lled by white sparitic calcite, septa replaced by black calcite.
71
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
2001; Döring 2002; Lubeseder et al. 2010). The maximum thickness of the Middle Devonian sedimentary succession in this small basin can be found east of Tazoulait and reaches over 700 m (Fig. 1; Döring and Kazmierczak 2001). The corresponding sequence in the Tafi lalt is much thinner and varies mostly between 30 m on the Tafi lalt Platform (e.g., at Bou Tchrafi ne, Hamar Laghdad or Filon Douze) and over 220 m at Ottara, which was probably situated on the slope
towards the Maïder Basin (Kaufmann 1998; Lubeseder et al. 2010). Throughout most of the eastern Anti-Atlas, the Middle Devonian sequence is dominated by limestone, marl and claystone alternations. The closer to the depocentre in the Maïder Basin, the greater gets the proportion of mudstones and the thicker the argillaceous proportion of the sequences (Kaufmann 1998; Lubeseder et al. 2010). On the Tafi lalt Platform, condensed sedimentation prevailed; cephalopod
Fig. 3. XRD-spectra of various fossils from the eastern Anti-Atlas. For additional results see Tab. 1. Samples kept with the number PIMUZ 36879.
72
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
limestones (dacryoconarid wackestones and packstones) are common and macrofossils occur in great numbers (Wendt 1988; Kaufmann 1998; Döring and Kazmierczak 2001). In the late Givetian, the clay content increases and thick claystone sequences were laid down particularly in the southern Maïder Basin while on the Tafi lalt Platform, sometimes carbonate sedimentation continued into the Frasnian (e.g., Ouidane Chebbi: Belka et al. 1999).
During the Late Devonian, synsedimentary tectonics intensifi ed in the eastern Anti-Atlas,
which is refl ected in extreme differences in facies and thickness (Hollard 1974; Wendt 1985, 1988; Wendt and Belka 1991; Belka et al. 1999). In the Maïder and Tafi lalt Basins, sedimentation was dominated by claystones with sideritic and a few carbonatic levels (often nodular such as the Thylacocephalan Layer). Simultaneously, cephalopod limestones, sandy limestones and thick-bedded crinoid or cephalopod limestones (wackestones and packstones) were laid down on the Tafi lalt Platform (Wendt 1985). The terminal Devonian sedimentary sequence of the
Fig. 4. Raman-spectra of Devonian invertebrates and vertebrates from the eastern Anti-Atlas. For additional results see Tab. 1. A, Cymaclymenia sp., PIMUZ 36863, Tafraoute. B, Cymaclymenia sp., PIMUZ 36868, Chouiref. C, Maxigoniatites sp., PIMUZ 36871, 12 km S of Dar Kaoua. D, Thylacocephala gen. et sp. indet., PIMUZ 36873, Madene El Mrakib. E, F, large chondrichthyan, PIMUZ 36881, Madene El Mrakib. G, arthrodire, PIMUZ 36877, Ouidane Chebbi. H, small chondrichthyan, PIMUZ XX, Madene El Mrakib.
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Hangenberg Black Shale is composed of fi ne-grained clastics in most sections (Kaiser et al. 2011; Klug et al. 2016). In the southern Tafi lalt, the correlate of the Hangenberg Sandstone is rather fi ne-grained and between 3 m and 28 m thick, while in the Maïder, the 5 m to 15 m thick massive sandstone beds form a high cliff in most of the region (Kaiser et al. 2011). The Hangenberg Sandstone is overlain by a several hundred meter thick clastic sequence of fi ne-grained sandstones, siltstones and claystones (latest Famennian to Viséan) with abundant trace fossils, occasional plant remains and very few thin shell beds (Kaiser et al. 2011), some containing ammonoids (e.g., Korn et al. 1999, 2002; Klug et al. 2006) and other
shelled fauna (benthic, nektonic and planktonic). Occasional wave ripples document rather shallow water.
Palaeoecology
In spite of the proximity of the Maïder and the Tafi lalt Basins, ecological differences are evident not only from sediment thickness and facies (Massa 1965; Hollard 1974; Kaufmann 1998) but also from the faunal composition of coeval strata, especially in the Middle and Late Devonian. Regional palaeoecology was examined by Frey et al. (2014, 2018) for the Early Devonian of the
Fig. 5. Geologic map of the eastern Anti-Atlas showing the supposed outlines of the Maïder and Tafi lalt Basins as well as the Tafi lalt Platform in the Late Devonian (modifi ed after Wendt & Belka 1991). We indicated the occurrences of cephalopod-bearing Konzentrat-Lagerstätten as well as of gnathostome-bearing Konservat-Lagerstätten. Note that the indicated Konzentrat-Lagerstätten represent only some examples of a much greater number of such Lagerstätten. The various shades of blue suggest differences in water depth in the Late Devonian with darker blue indicating greater depth.
74
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
southern Tafi lalt and the Famennian to Tournaisian and locally for the Pragian to Eifelian by Klug et al. (2018). The differences in palaeoecological dynamic shifts through the Devonian in the two basins refl ects the special position and palaeo-environment of the Maïder Basin and is required for the explanation of the Famennian Konservat-Lagerstätten in the southern Maïder.
Lochkovian and Pragian
In the Lochkovian of Tafi lalt and Maïder, fossiliferous layers are rare and usually dominated by remains of nektonic to planktonic organisms like cephalopods with orthoconic conchs and graptolites (Frey et al. 2014). In the Maïder, the Lochkovian is not so well exposed because its sediments are mostly argillaceous with little carbonate. The high clay-content indicates moderately deep water with low oxygen conditions near the sediment surface.
Towards the top of the Lochkovian sequence, the carbonate content rises, fossils become more abundant and some bivalves as well as gastropods are present. This suggests an increasing oxygenation of the water column during the Pragian and early Emsian (as refl ected by high invertebrate diversities in the Tafi lalt and highly diverse trilobite faunas in the Maïder; Morzadec 2001; Frey et al. 2014; Klug et al. 2018). The increasing oxygenation eventually reached the top centimetres of the sediment (refl ected in occurrences of trace fossils: e.g., Klug & Hoffmann 2018), possibly in correlation with a reduced water depth. Vertebrate remains are rare in the Lochkovian and Pragian; some pectoral fi n spines of Machaeracanthus are found (Frey et al. 2014).
Emsian
Oxygen content continued to fl uctuate in the Emsian of the eastern Anti-Atlas, probably controlled by sea-level to some extent (Klug et al. 2008; De Baets et al. 2010; Frey et al. 2014; Aboussalam et al. 2015; Klug et al. 2018). Facies changes in the Tafi lalt and Maïder are rather uniform in the sense that changes from argillaceous to carbonate sedimentation occurred roughly synchronously in the Emsian (Massa 1965; Hollard 1974; Kaufmann 1998). In the Emsian sediments, geographical differences in facies, sediment thickness and fossil content are still low and correspondingly, the marine basins of the eastern Anti-Atlas did not change ecologically very much geographically. Although the oxygen content was likely varying, both benthic and non-benthic diversity stayed reasonably high until the end of the Zlíchovian (early Emsian; Massa 1965;
Frey et al. 2013, 2018). With the Daleje-transgression (basal Late
Emsian), overall diversity was reduced (but this might also be an effect of increased sediment accumulation rates) and benthics are much less abundant (Frey et al. 2014; Klug et al. 2018). Occasionally, trilobites, tabulate and rugose corals occur as well as small orthocerids and ammonoids, mostly preserved in goethite. It is well conceivable that the oxygen content of the lower part of the water column was low again linked to the transgression (Haq and Schutter 2008). During the latest Emsian, carbonate deposition resumed and diversity increased markedly including benthos (trilobites, gastropods, bivalves etc.), plankton (mostly dacryoconarids and orthocerids) and nekton (several ammonoid taxa, rare gnathostomes), refl ecting both a lower sea-level and improved sea-fl oor oxygenation (Frey et al. 2014; Klug et al. 2018). Particularly in the Maïder, late Emsian strata yielded several highly spinose trilobite taxa (e.g., Morzadec 2001; Chatterton and Gibb 2010).
The demersal acanthodian Machaeracanthus can locally be very abundant in the early Emsian (Klug et al. 2008; De Baets et al. 2010) and various placoderm taxa occur: remains of large arthrodires can be found in the late Zlíchovian (early Emsian) and the Dalejan (late Emsian) yielded remains of Atlantidosteus hollardi and Antineosteus lehmani in various localities of the Tafi lalt (Klug et al. 2008; Lelièvre 1984, 1995; Lelièvre et al. 1993, Rücklin and Clément 2017 ; Rücklin et al. 2018). The wealth of –sometimes large- invertebrate prey organisms represented the trophic base to sustain such large predators, which reached body lengths exceeding one meter.
Eifelian and Givetian
At the beginning of the Eifelian, the carbonate production increased further and some massive limestone beds were deposited, interrupted only by the Choteč-transgression. On the Tafi lalt Platform, the carbonates overlying the dark sediments of this transgression show many indications for condensed sedimentation such as eroded fossils, iron oxide-stained layers, high abundance of more or less fragmented mollusc conchs etc. The fauna is dominated by cephalopods (ammonoids, orthocerids, oncocerids, bactritids) and dacryoconarids, but bivalves (abundant), crinoids, trilobites, brachiopods and gastropods also occur. Overall, benthos plays a subordinate role, while nektonic and planktonic organisms are both diverse and abundant.
In the Maïder, carbonates prevail as well, but the sequences are much thicker and less fossiliferous (e.g., Jebel El Otfal, eastern Jebel El Mrakib,
75
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Jebel Issoumour), thus suggesting a greater water depth. Until the end of the Eifelian, the carbonate and fossil content fl uctuated gently (Massa 1965), likely refl ecting a mix of eustatic and regional sea-level changes (cf. Kaufmann 1998; Haq and Schutter 2008). Following the early Eifelian Choteč-Event and the late Eifelian Kačák-Event, the clay and organic content increased and locally, fossils are preserved in iron oxides.
On the Tafi lalt Platform, carbonate deposition lasted through the entire or at least parts of the Givetian. In the basal Givetian, ammonoids and other cephalopods occur in a moderate abundance and diversity. Especially in the northern Tafi lalt, the sometimes massive limestone beds are full of trace fossils, indicating a good oxygenation of the sea-fl oor. In the southern Tafi lalt, the early Givetian contains allochthonous sediments full of corals and brachiopods; these organisms possibly lived in somewhat shallower water.
From the Tafi lalt Platform towards the Tafi lalt and Maïder Basin, the Givetian sections become marly or clayey close to the base of the Frasnian. As far as invertebrate fossil preservation is concerned, it changes accordingly from carbonatic internal moulds (sometimes with calcitic shell; e.g., Bockwinkel et al. 2009) to goethite where the clay content reaches higher levels (e.g., at Hassi Nebech; Bensaïd 1974; Bockwinkel et al. 2013). Cephalopod diversity became rather high towards the end of the Givetian with tens of ammonoid species (Bockwinkel et al. 2015, 2017) as well as other cephalopods and only rare benthics. On the slope from the Tafi lalt to the Maïder Basin (Jebel Amessoui, Ottara), allochthonous layers rich in corals, stromatoporoids, crinoids and brachiopods alternate with argillaceous layers, yielding a more pelagic fauna. This documents an increase in water depth (Lubeseder et al. 2010).
The light grey Eifelian to early Givetian carbonates and claystones of the Maïder do yield occasional invertebrate remains such as corals, crinoids, brachiopods, trilobites, etc. Particularly at Jebel Rheris, Jebel Issoumour, Jebel Oufatene, Madene El Mrakib and around the reef-mound Aferdou El Mrakib, reef fauna occurs in more or less rock-forming amounts, sometimes in the form of biostromes or carbonate build-ups (Kaufmann 1998; Fröhlich 2006; Tessitore et al. 2013, 2016). Towards the end of the Givetian, carbonate production decreased and locally (particularly in the depocentre), ammonoid associations occur that show the same goethite-preservation as in the Tafi lalt Basin (Bockwinkel et al. 2015).
Machaeracanthus cf. peracutus continues into the Eifelian of Tafi lalt and Maïder, but it is less abundant than in the Emsian. From the Tafi lalt and Maïder, Lelièvre et al. (1993) and Rücklin and Clément (2017) further report the
placoderms Maideria falipoui Eastmanosteus sp. and Hollardosteus marocanus. Remains of large arthrodires possibly belonging to Eastmanosteus were found both in the strata following the Choteč- and Kačák-Events of Filon Douze and Ouidane Chebbi. Chondrichthyan teeth of Omalodus schultzei and Phoebodus fastigatus from the Givetian of the southern Tafi lalt Platform were also reported (Hampe et al. 2004; Kaufmann 1998). Additionally, the dipnoan Dipnotuberculus gnathodus was described from the Maïder (Campbell et al. 2002). In any case, this moderate diversity of vertebrate predators of varying size suggests that the invertebrate fauna provided enough prey organisms for these predators to thrive.
Frasnian
As mentioned above, lateral and vertical facies changes are more pronounced than during the Early and Middle Devonian. This suggests an increasing ecological differentiation of the region.
At the latest with the beginning of the Frasnian, argillaceous sedimentation began in most parts of the Tafi lalt Basin, the Maïder Basin and even on parts of the Tafi lalt Platform, refl ecting rising sea-levels (e.g., Wendt 1988; Kaufmann 1998; Lubeseder et al. 2010). At the same time, strongly condensed sedimentation happened in the Frasnian in the southwestern Maïder and on the northern Tafi lalt Platform (e.g., Wendt 1988; Wendt and Belka 1991; Hüneke 2006). Therefore, there was likely a stronger differentiation in both water depth and oxygen availability.
Frasnian to early Famennian sediments often display dark colours and have a high organic content with abundant iron-bearing minerals (‘Kellwasser Facies’ sensu Wendt and Belka 1991), refl ecting the high organic productivity on land (abundant wood fragments) and in the sea as well as the low oxygen of the lower water layers. This is corroborated by the facts that these sediments are rather poor in benthic fauna. In spite of the widespread low oxygen content, there still was enough oxygen for some organisms as documented in local trace fossil assemblages (e.g., Filon Douze; own fi eld data).
In the central Tafi lalt Platform, carbonate sedimentation persisted throughout much of the Late Devonian (Wendt 1985) and brachiopods, crinoids, bivalves, gastropods, as well as small rugose corals occur in a mostly low diversity and moderate to low abundance (own observations; compare, e.g., Massa 1965). The Kellwasser Limestone as well as some early and middle Famennian limestones can be very rich in fossils, but mostly cephalopods (occasionally, brachiopods, gastropods, bivalves, trilobites and
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solitary corals also occur in low to moderate numbers).
Although the early Frasnian deposits are rather poor in vertebrates, the late Frasnian sediments yielded a rich vertebrate assemblage. For example, Rücklin and Clément (2017) listed the genera Enseosteus, Walterosteus, Rhinosteus, Draconichthys, Erromenosteus, Brachyosteus, Brachydeirus, Oxyosteus, Dinomylostoma, Holonema, and Aspidichthys. As far as chondrichthyans are concerned, Derycke (2017) reported fi n spines of Ctenacanthus sp.
In the southeastern of the Maïder Basin (Madene El Mrakib, Rich Bel Ras), the Kellwasser levels are represented by dark and massive cephalopod limestones (Wendt and Belka 1991). These sediments are rich in Archaeopteris-wood (Meyer-Berthaud et al. 1999), sometimes overgrown by holdfasts of some of the oldest pseudoplanktonic crinoids (Klug et al. 2003).
Famennian
Much of the Famennian succession is argillaceous in the Maïder and condensed carbonatic on the Tafi lalt Platform. In both regions, the Famennian is rich in diverse cephalopod associations (e.g., Korn and Bockwinkel 2017 and references therein); these fossils are preserved either in goethite or in carbonates (based on comparisons with our analysed samples; see Tab. 1). In combination with the mostly scarce benthic fauna, this suggests low oxygen levels of the bottom waters. In the middle and late Famennian of the Tafi lalt, limestones of locally strongly fl uctuating thickness occur, which also vary strongly in their fossil content (cephalopods, crinoids, brachiopods), documenting phases of moderate to good aeration in more or less shallow water conditions (e.g., Wendt et al. 1984; Wendt 1988).
Remarkably, the sediments of the Hangenberg Black Shale contain abundant ammonoids, occasionally orthocerids, small trace fossils, abundant bivalves and other fossils (Klug et al. 2016). The massive sandstones above indicate a regressive regime and likely were deposited during the end-Famennian regression (Kaiser et al. 2011; Becker et al. 2018). Palaeoecological changes throughout the Famennian and Tournaisian of the southern Maïder were studied by Frey et al. (2018).
Around the Devonian/ Carboniferous boundary, palaeobiodiversity is usually low. Some silt- and sandstone beds contain abundant brachiopods and there are also some layers rich in cephalopods. Starting from the latest Devonian into the Viséan, trace fossils can be diverse and abundant (Cruziana-like and Rusophycos-like traces, Diplichnites, Asteriacites etc.).
In spite of the great end-Frasnian mass extinction, which left its impressive traces also in Morocco (Buggisch 1991; Wendt and Belka 1991; Rücklin 2010, 2011), the Famennian vertebrate diversity is even higher than that of the Frasnian. Apparently, vertebrate assemblages recovered during the early Famennian. Accordingly, a great number of placoderm taxa were found in the Tafi lalt: Selenosteidae gen. et sp. indet., Dunkleosteus marsaisi, D. terrelli, Tafi lalichthys lavocati, Mylostomidae gen. et sp. indet., Titanichthys termieri and Alienacanthus sp. (Lehman 1956, 1964, 1967; Frey et al. 2018). Rücklin and Clément (2017) also report sarcopterygians of the families Actinistia and Tristichopteridae (Lehman 1977, 1978; Lelièvre and Janvier 1986). The number of chondrichthyan taxa is even more impressive. Derycke (1992, 2017) as well as Ginter et al. (2002) listed numerous taxa from the Tafi lalt.
In the Maïder, oxygen-depleted conditions recurred repeatedly in the lower part of the water column, which were not suited for such more demersal durophagous chondrichthyans to survive over a prolonged time. By contrast, chondrichthyans with grasping dentition such as the phoebodontids and cladodonts were probably living in the water column (Ginter et al. 2010) and thus, oxygen-poor conditions in the bottom water represented only a minor problem for them. Following Ginter (2000, 2001), we thus interpret the Maïder chondrichthyan assemblage as belonging to the “intermediate Phoebodus-Thrinacodus biofacies […] of moderately deep shelves”. In addition to the vertebrates listed above, we found skulls of onychodontids in the middle Famennian, which await their description. According to these published occurrences, the palaeobiodiversity of chondrichthyans surpassed that of placoderms following the Kellwasser Facies in the Tafi lalt.
Exceptional preservation and Fossil-Lagerstätten
Already in 1970, Seilacher coined the term “Fossil-Lagerstätte”, which is widely used today (Seilacher et al. 1985; Bottjer et al. 2002). He sub-classifi ed Fossil-Lagerstätten into Konservat-Lagerstätten and Konzentrat-Lagerstätten.
Konzentrat-Lagerstätten of the eastern Anti-Atlas
This kind of Fossil-Lagerstätte is characterized by a vast amount of specimens that do not necessarily have to be particularly well-preserved (e.g., Seilacher et al. 1985; Seilacher 1990; Bottjer et al. 2002). In the eastern Anti-Atlas, this kind of
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Fossil-Lagerstätte is quite common. Thus, it is impossible to provide a comprehensive list. We are focusing here on cephalopods, although there are also Konservat-Lagerstätten of, e.g., crinoids (e.g., Scyphocrinites/ Camarocrinus, Silurian/ Devonian boundary), brachiopods (e.g., Ivdelinia and Devonogypa, Middle Devonian), corals (e.g., Phillippsastrea, Middle Devonian), mixed benthic communities (e.g., Red Fauna; Klug et al. 2018) and other invertebrates in the eastern Anti-Atlas. Some conspicuous examples of cephalopod mass occurrences (Fig. 5, 6) are listed below:
1. Low diversity mass occurrences of the orthocerid Temperoceras ludense and other cephalopods in the late Silurian (Polygnathoides siluricus conodont Zone) and late Lochkovian (Kröger 2008);
2. High diversity cephalopod accumulations (Fidelites spp., Subanarcestes marhoumensis, Pinacites jugleri, Crispoceras spp., Lobobactrites sp., Oncocerida, Orthocerida) in the early Eifelian (Pinacites jugleri ammonoid Zone) of the southern Tafi lalt Platform (e.g., Filon Douze/ Jebel Ouaoufi lal; Klug 2002; Kröger 2008);
3. High diversity cephalopod accumulations (many species of Allopharciceras, Extropharciceras, Petteroceras, Pharciceras, Pseudoprobeloceras, Oxypharciceras, Sympharciceras, Tornoceras, Orthocerida, Oncocerida) in the late Givetian (e.g., Synpharciceras clavilobum ammonoid Zone) of the northern Tafi lalt Platform (Bockwinkel et al. 2009, 2017);
4. Moderate diversity cephalopod accumulations (several species of Archoceras Beloceras, Carinoceras, Crickites, Manticoceras, Tornoceratidae, Orthocerida, Oncocerida) occur in several layers, some of which associated with remains of arthrodires (upper Palmatolepis rhenana – Pa. linguiformis conodont Zones; Rücklin 2010, 2011) and Archaeopteris wood fragments in the Kellwasser Limestone of the Tafi lalt Platform and the southeastern Maïder (Wendt and Belka 1991);
5. Moderate diversity cephalopod accumulations (several species of Armatites, Cheiloceras, Falcitornoceras, Maeneceras, Paratorleyoceras, Polonoceras, Orthocerida, Oncocerida, Brachiopoda) in the early Famennian (Cheiloceras subpartitum to Paratorleyoceras globosum ammonoid Zones) of the Tafi lalt Platform and the southeastern Maïder (Becker 2002).
6. Low diversity cephalopod accumulations (several species of Platyclymenia, Prionoceras, Orthocerida) in the middle Famennian (Platyclymenia annulata Zone) of the Tafi lalt Platform and the southeastern Maïder region (Korn 1999). This stratigraphic interval often also yields placoderm remains of Dunkleosteus, in the Maïder even complete skeletons in huge nodules up to 4 m long (Lehman 1956, 1964, 1976).
7. Moderate diversity cephalopod accumulations (several species of Alpinites, Cymaclymenia, Cyrtoclymenia, Discoclymenia, Endosiphonites, Erfoudites, Falciclymenia, Gundolfi ceras, Mimimitoceras, Platyclymenia, Posttornoceras, Praeglyphioceras, Prionoceras, Orthocerida) of the late Famennian Clymenia Stufe (Gonioclymenia ammonoid genozone; e.g., Korn 1999). This interval contains also abundant microremains of chondrichthyans in the southern Tafi lalt (Ginter et al. 2002).
In the Middle Devonian, there are numerous localities with Konzentrat-Lagerstätten of more or less allochthonous reefal faunal assemblages; true reefs and biostromes are rare in the eastern Anti-Atlas (Fröhlich 2003). These moderate diversity accumulations of reef fauna may contain the following taxa: Phillipsastrea sp., Xystriphyllum sp., Heliophyllum halli moghrabiense, Cystiphylloides sp., Acanthophyllum sp., Thamnopora spp., auloporids, favositids, heliolitids, brachiopods, crinoids, stromatoporoids (e.g., Kaufmann 1998).
Konservat-Lagerstätten of the eastern Anti-Atlas
Also called conservation lagerstätten, these deposits received their name from their unusual preservation of animals or body parts that are normally not preserved (Seilacher 1970, 1990). The most famous Palaeozoic Konservat-Lagerstätte of Morocco occurs undoubtedly in the Fezouata Formation, which was compared to the classical Konservat-Lagerstätte of the Burgess Shale (van Roy et al. 2010). The term Konservat-Lagerstätte implies exceptional preservation of soft tissues, be they part of an organism with or without hard parts. The Devonian of Morocco is known for localities yielding articulated skeletons of various organisms such as trilobites, crinoids and also fi shes, but soft parts were not documented previously and thus, Konservat-Lagerstätten in a stricter sense were also unknown.
Recently, we described a fauna from the latest Famennian Hangenberg Black Shale of
78
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Fig. 6. Examples of Konzentrat-Lagerstätten (concentration lagerstätten) in the eastern Anti-Atlas. A, Mass occurrences of Temperoceras ludense and other cephalopods in the late Silurian, Ouidane Chebbi. Width about 1.5 m. B, High diversity cephalopod accumulation in the Eifelian of Filon Douze. C, Moderate diversity cephalopod accumulations (mainly Gephuroceratidae) in the Frasnian Kellwasser Limestone of Jebel Amelane. Width ca. 0.5 m. D, Moderate diversity reef fauna assemblage dominated by thamnoporids, Eifelian, Madene El Mrakib. E, F, Moderate diversity cephalopod accumulations (mainly cheiloceratids, orthocerids and brachiopods) in the early Famennian of Taouz (E) and Madene El Mrakib (F). G, H, Low diversity cephalopod accumulations (mainly Platyclymenia) in the middle Famennian (Platyclymenia annulata Zone) of Tachbit/ Mkarig (G) and Madene El Mrakib (H); width (in H) ca. 0.7 m.
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the southern Maïder (Klug et al. 2016). These deposits yielded abundant non-mineralized cephalopod jaws, a few carbonized plant remains (algae), articulated arthropod remains lacking mineralized cuticles and also organic parts inside ammonoid body chambers that likely represent soft part remains. Accordingly, this deposit could be considered a Konservat-Lagerstätte because of articulated remains of skeletons and the preservation of abundant non-mineralized tissues.
Near the early to middle Famennian boundary (probably Palmatolepis rhomboidea or Pa. marginifera conodont Zone), we discovered a reddish argillaceous layer a few tens of centimeters thick and rich in iron oxides in the southern Maïder (Frey et al. 2018). This layer is characterized by abundant fl at nodules, mostly 50 to 100 mm in diameter and usually containing the carapaces and sometimes (primarily chitinous) appendages, eyes, gills, and possibly other organs (ongoing research) of thylacocephalans (Fig. 7, 8). This Thylacocephalan Layer (Frey et al. 2018) also yields articulated gnathostome remains, mostly of chondrichthyans, especially cladoselachian-like forms, symmoriids and phoebodontids as well as sarcopterygians and various arthrodires (Fig. 9, 10). Placoderms are commonly preserved in huge nodules, which likely refl ect the outline of the entire body (Fig. 9). As far as the chondrichthyans are concerned, we found remains of musculature, liver, digestive tract with prey remains, lateral lines, body outline, integument and cartilage (the latter being calcifi ed primarily, but still having a low preservation potential; Fig. 10). The preservation of such structures in articulated skeletons are classical characters of a Konservat-Lagerstätte (e.g., Seilacher et al. 1985).
Seilacher et al. (1985: fi g. 11) further refi ned the classifi cation of Konservat-Lagerstätten in a triangle (Fig. 12). Its corners are labelled ‘obrution’ (sedimentational régime; organic remains quickly
covered by sediment), ‘stagnation’ (hydrographic régime; organic remains preserved due to low oxygen levels) and ‘bacterial sealing’ (early diagenetic régime; bacterial fi lms replace or surround soft tissues, sometimes also fostering rapid phosphatisation; e.g., Kear et al. 1995).
The fossils of the Thylacocephalan Layer are preserved in a set of minerals including mainly hydroxyapatite, haematite, iron hydroxides, pyrite, siderite and quartz (Tab. 1). As discussed above, the iron oxides and hydroxides likely are products of slow weathering of primary pyrite in both the vertebrates and invertebrates (rarely, remains of which are preserved). This reduces the list of primary (now altered) minerals to phosphates and pyrite. Other Konservat-Lagerstätten with fossils preserved in pyrite and phosphates are the famous Early Devonian Hunsrück Slate and the Early Jurassic Posidonia Slate (Seilacher et al. 1985). Seilacher et al. (1985) somewhat arbitrarily placed these two Konservat-Lagerstätten in two different parts of the proposed ternary diagram of Konservat-Lagerstätten. While the Posidonia Slate is placed in the stagnation corner, the Hunsrück Slate (and also Solnhofen) are half way between the stagnation corner and the obrution corner, because post mortem transport and mass fl ows rapidly covering organic remains played an important role. In the case of Solnhofen, bacterial mats were also important, shifting its position towards the ‘bacterial sealing’ corner. Evidence for transport, obrution and bacterial mats have not been detected in the Devonian Thylacocephalan Layer. In combination with the facts that the Maïder Basin was a restricted basin with water exchange being limited by the Tafi lalt Platform and the scarcity of benthic organisms in the Thylacocephalan Layer, the Konservat-Lagerstätte of the Thylacocephalan Layer and other fossiliferous layers of the Famennian in that region are here assigned to
Fig. 7. The Thylacocephalan Layer (early middle Famennian) in the southern Maïder (Madene El Mrakib). A, thylacocephalan-bearing concretions in situ. B, surface accumulation of thylacocephalan-bearing nodules.
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
Fig. 8. Phosphatic preservation of thylacocephalans from the Thylacocephalan Layer (early middle Famennian) in the southern Maïder (the orange-coloured sparitic fi lling is calcitic), PIMUZ 36872. A, lateral view of a carapace. B, broken specimen showing parts of the appendages preserved in apatite (Tab. 1).
Fig. 9. Preservation of gnathostomes from the Thylacocephalan Layer (early middle Famennian) in the southern Maïder. A, undescribed placoderm (? Driscollaspis sp.), PIMUZ 36882, Rich Bel Ras; note the preserved dorsal fi n and the caudal fi n (the concretion traced the body outline). B, cladoselachid chondrichthyan, PIMUZ 36883, Madene El Mrakib; preserved with several haematitic soft parts; note the ridge around the body that likely formed when the carcass sank into the mud ‒ the body itself collapsed later due to decay and sediment compaction, leaving a shallow depression.
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Chapter II: Fossil-Lagerstätten and Preservation of Fossils
the stagnation corner. Another shared character underlining the taphonomic similarity to the Posidonia Slate is the stratigraphically (much of the early and middle Famennian; Webster et al. 2005) and geographically widespread occurrence of pseudoplanktonic crinoids in the middle Famennian of both the Maïder and the southern Tafi lalt Platform (Klug et al. 2003; Webster et al. 2005; own unpublished fi eld data; Fig. 11).
In the attempt to classify marine Konservat-Lagerstätten in a more coherent way we use 31
characters predominantly based on Seilacher (1985). 19 well-known Konservat-Lagerstätten and the two herein described ones of the Devonian of Morocco were coded accordingly and analyzed in a Principal Component Analysis (Fig. 13). Remarkably, the Burgess-type Lagerstätten plotted in a fi eld well separated from the black shales and the Plattenkalke plotted again in a distinct fi eld. A black shale fi eld contains both Moroccan Konservat-Lagerstätten at opposite ends with the Thylacocephalan Layer being
Fig. 10. Soft-tissue preservation of a cladoselachid chondrichthyan, PIMUZ 36884, Thylacocephalan Layer (early middle Famennian), Madene El Mrakib (same specimen as in Fig. 12B. A, thoracal region directly anterior to the pelvic fi n with mineralized soft parts (muscles, neural arch cartilage, liver). B, detail of A showing muscle fi bres.
Fig. 11. Detail of a huge colony (1.10 m long with over 70 calyces) of the pseudoplanktonic crinoid Moroccocrinus ebbinghauseni from the late early Famennian of Jebel Ouaoufi lal. The Archaeopteris log is not preserved but was likely at the top of the image (note the difference in stem alignment on top and in the lower three quarters), running parallel to the hammer, and burying some of the crinoids below it. The colony was already excavated and is seen from below; on the other side, the degree of articulation is much lower.
82
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
close to La Voulte (which share the abundance of echinoderms, arthropods and ammonoids) and the Hangenberg Black Shale being close to Mazon Creek. This underlines the important role of low oxygen levels in the Maïder Basin during the Famennian, as proposed already by Frey et al. (2018).
Conclusions
We chemically analysed various Devonian and Early Carboniferous fossils from the eastern Anti-Atlas. Ammonoids and other cephalopods from this region and time interval are preserved in calcite, goethite (sometimes with haematite), quartz, baryte (only in the Early Carboniferous; Korn 1988), and clay minerals. As far as vertebrates and the thylacocephalansare concerned, we found the same minerals except baryte but with hydroxyapatite. In particular, the results show that the chondrichthyan musculature is now predominantly preserved in goethite and haematite. Both placoderm bones and chondrichthyan cartilage are preserved in apatite (mainly hydroxyapatite and probably also francolite). Especially the abundance of iron oxides and hydroxides suggest that some of these fossils were originally preserved in pyrite (at least partially), which was altered due to deep
weathering in the desert environment. This is corroborated by rare fi nds of completely pyritized fossils from the same strata in depths of over 10 m below today’s surface and by pyrite remains in the centre of some only partially oxidized fossils.
In turn, this primary abundance of pyrite (now goethite and iron hydroxides) in combination with the clayey facies and the scarcity of benthos in some strata suggest that the Thylacocephalan Layer containing exceptionally preserved gnathostomes was deposited under oxygen-poor conditions (Klug et al. 2016, Frey et al. 2018). This is supported by the palaeogeographical situation of the Maïder Basin (Fig. 4) that was closed to the south and north by land, while to the east and west, the shallower regions of the Tafi lalt Platform and the Maïder Platform limited water exchange (Wendt 1988; Kaufmann 1998).
Hypoxic to anoxic conditions in the bottom waters explain the absence of protacrodontids, which mainly occur in shallower, better oxygenated waters (Ginter 2000). Clairina and Jalodus likely preferred deeper environments than the one in the Maïder Basin. Following Ginter (2000), the taxa present in the Maïder (Phoebodus and cladodonts) point at an intermediate water depth.
Taking the exceptional fossil preservation (soft-tissue preservation), composition of the fossil assemblages (scarcity of benthos and demersal forms), the mineralogic composition of the fossils (primary pyrite, phosphates) and
Fig. 12. Ternary diagram of the three main types of conservation deposits of Seilacher et al. (1985). Some of the most famous examples are indicated by circles; note that the positions of the circles are somewhat arbitrary, partially because the respective roles of the main factors like, e.g., obrution and stagnation, change within these deposits and across the sedimentary basins. Also, there is no quantitative measure yet to place Lagerstätten within this diagram. In any case, obrution plays a much larger role in the famous Cambrian deposits compared to the Mesozoic black shales as well as the here portrayed Late Devonian Konservatlagerstätten from the eastern Anti-Atlas.
83
Chapter II: Fossil-Lagerstätten and Preservation of Fossils
the palaeogeographic setting into account, the Famennian Thylacocephalan Layer is a Konservat-Lagerstätte. Since indications for mass movements, current alignment and traces of microbial activity sealing organismic remains have not been found, the Thylacocephalan Layer and the Hangenberg Black Shale are here considered as two examples of stagnation Lagerstätten sensu Seilacher et al. (1985) and thus the fi rst two of this kind from the Devonian of northern Africa (Fig. 12, 13). In our Principal Component Analysis of marine Konservat-Lagerstätten, these two Moroccan Lagerstätten plotted in the fi eld with of the black shales such as, e.g. the Triassic ones of Austria, Switzerland and China, the Jurassic ones of Europe etc. This new approach, based on the questionnaire by Seilacher et al. (1985), allows a more objective classifi cation of Konservat-Lagerstätten.
Acknowledgements. ‒ We greatly appreciate the support of the Swiss National Science Foundation for fi nancial support of our research projects (Project Numbers 200020_132870, 200020_149120, 200021_156105). We thank the colleagues of the Ministère de l’Energie, des Mines, de l’Eau et de l’Environnement (Direction du Développement Minier, Division du Patrimoine, Rabat, Morocco) who provided working and sample export permits. Saïd
Oukherbouch (Tafraoute) and René Kindlimann (Aathal, Switzerland) helped in the fi eld. Lydia Zehnder and Sebastian Cionoiu (both Earth Sciences Department, ETH Zürich) are thanked for their generous help with the XRD- and Raman-analyses. We acknowledge the constructive reviews of XX and XX.
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Fig. 13. Principal Component Analysis of some marine Konservat-Lagerstätten. Classifi cation based on Tab. 3, which is based on the questionnaire by Seilacher et al. (1985). Note the perfect grouping of early Palaeozoic Burgess type Lagerstätten, Black Shale Lagerstätten and the Plattenkalke. Also note that the two Famennian Lagerstätten from Morocco plot at the limits of the Black Shale Lagerstätten.
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Appendix I
Tab. 4. Tübingen questionnaires Fossil-Lagerstätten (after Seilacher et al. 1985).
CHAPTER III
Morphology, phylogenetic relationships and ecomorphology
of the early elasmobranch Phoebodus
Linda Frey, Michael Coates, Michal Ginter, Vachik Hairapetian, Martin Rücklin und Christian Klug
In preparation, formatted for Proceedings B
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Morphology, phylogenetic relationships and ecomorphology of the
early elasmobranch Phoebodus
Linda Frey1, Michael Coates2, Michał Ginter3, Vachik Hairapetian4, Martin Rücklin5, Iwan Jerjen6 and Christian Klug1
1Paläontologisches Institut und Museum, University of Zurich, Karl-Schmid-Strasse 4, CH-8006 Zürich ([email protected]; [email protected]) 2Department of Organismal Biology and Anatomy, University of Chicago, 1027 E. 57th St., USA-60637 Chicago3Faculty of Geology, University of Warsaw, al. Żwirki i Wigury 93, PL-02-089 Warszawa4Department of Geology, Khorasgan Branch, Islamic Azad University, PO Box 81595-158, Esfahan, Iran5Naturalis Biodiversity Center, Postbus 9517, 2300 RA, Leiden, The Netherlands6Institute for Biomedical Engineering, ETH Zürich, Gloriastrasse 35, CH- 8092 Zürich
Although the anatomical knowledge of early chondrichthyans and thus their phylogeny is constantly im-proving, some taxa are still known only by microremains. Assumptions about the ecomorphology of the nearly cosmopolitan and regionally abundant Devonian chondrichthyan genus Phoebodus and the phy-logenetic relations to other phoebodontids were solely based on teeth and fi n spines. Here, we report the fi rst body remains and braincases of Phoebodus from the Famennian (Late Devonian) of the Maïder re-gion of Morocco. Phoebodus differs from other phoebodontids such as Thrinacodus in following features: an anguilliform but less slender body, a short otic process on the palatoquadrate, a derived shape of the ceratohyals and the presence of two dorsal fi n spines. Our phylogenetic analyses confi rm phoebodontids (Phoebodus and Thrinacodus) as stem elasmobranchs (crown Chondrichthyes). Phoebodontids form a polytomy together with Cladodoides, Tamiobatis, xenacanthids and hybodontids. They represent the earli-est anguilliform chondrichthyans in the fossil record and therefore underline the Devonian morphological disparity and ecological diversity of early gnathostomes.
Keywords: Gnathostomes, Chondrichthyes, neurocranium, homoplasy, Devonian, Morocco
1. Introduction
During the last decades, new records of ear-ly chondrichthyans ameliorated our anatomical knowledge of these jawed fi sh[1-15]. Although occasionally, articulated and complete skeletons of Palaeozoic chondrichthyans were discovered, some groups of early chondrichthyans are still exclusively known from microremains or mac-roscopic isolated hard parts such as teeth and fi n spines [16-18]. Accordingly, the skeletal anatomy of phoebodontids was entirely unknown until the discovery and description of Thrinacodus gra-cia [19] from the Serpukhovian locality of Bear Gulch, Montana. Thrinacodus gracia shows a highly derived body plan compared to other early chondrichthyans in having an extremely slender and elongate body as well as asymmetric tricus-pid teeth with a recurved crown [19-20]. Howev-er, complete crania or other skeletal remains of the common phoebodontid Phoebodus were un-known, even though their characteristic tricuspid
teeth (and tentatively, isolated fi n spines [Maisey in 18]) were recovered from numerous localities of Middle Devonian to Early Carboniferous age worldwide [18, 21-29].
Based on their abundant teeth, evolution-ary scenarios of members of the Phoebodontidae were postulated from symmetric teeth with broad bases (Ph. fastigatus [23], Ph. latus [24], Ph. bi-furcatus [23]) of Frasnian and earliest Famennian age to asymmetric tricuspid teeth with narrow bases of late Famennian age (Thrinacodus tran-quillus [30], Th. ferox [31]) [18]. The early/ mid-dle Famennian Phoebodus gothicus transitans already displays some asymmetry in base and crown and therefore, this species was inferred to represent a phylogenetic link between Phoebodus and Thrinacodus [26].
Here, we describe one nearly complete skel-eton and several three-dimensionally preserved skulls of Phoebodus that were discovered in the
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middle Famennian of the Maïder Basin of Moroc-co. We discuss the morphological similarities to the phoebodontid Thrinacodus gracia and its phy-logeny as well as ecology. We also discuss which impact the new morphological data of Phoebodus has on the ecomorphological diversity of Devoni-an chondrichthyans.
2. Material and methods
a) Specimens
The material includes visceral and postcranial re-mains of a skeleton of Phoebodus saidselachus sp. nov. (PIMUZ A/I 4712) as well as four three-di-mensionally preserved cranial remains (PIMUZ A/I 4656, 4710, 4711, 4713) that are housed at the Palaeontological Institute and Museum of the University of Zurich, Switzerland. Over the last decades, the material was collected from Madene El Mrakib, which is situated in the southern Maïder region of the eastern Anti-Atlas of Moroc-co (Fig. S1). The skeletal remains are preserved in ferruginous nodules of reddish colour found in the Thylacocephalan Layer (formerly described as Phyllocarid Layer; [32]) in which thylacoceph-alan arthropods are highly abundant. Dating of the host rocks by index ammonoids (Maeneceras horizon) suggest an early to middle Famennian age [33, 34].
(b) Anatomy inferred from CT-data
Computed tomograms of the three-dimensionally preserved skulls were acquired using a Nikon XT H 225 ST industrial CT-scanner at the University of Zurich, Switzerland. The braincase of PIMUZ A/I 4711 preserving parts of the otic and occiput yielded an image stack with good contrast be-tween matrix and fossil. Data acquisition and im-age reconstruction parameters: 221 kV, 349 mA; fi lter: 2 mm of copper; voxel sizes in mm: 0.0776 in each direction; the data was exported as a raw volume.
The volume was manually segmented and anatomical reconstructions were performed using the software Mimics v.17 (http://www.biomedi-cal.materialise.com/mimics; Materialise, Leuven, Belgium). Smoothing, colours and lighting were edited in MeshLab v. 2016 (http://www.meshlab.net; [35]) and blender v2.79b (https://www.blend-er.org; Amsterdam, Netherlands).
(c) Phylogenetic analyses
Our phylogenetic data matrix is based on those of Coates et al. [5] and Brazeau [36]. Data on ac-anthodian stem chondrichthyans are from Davis et al. [37] and Burrow et al. [38] while Zhu et al. [39] and Qiao et al. [40] provide data from the out-group. We updated the character matrix by adding character 58 (ceratohyal anteriorly blade-shaped) and by excluding 35 uninformative characters, which is the result of the adapted taxa list (22 taxa of stem gnathostomes were excluded; see supple-mentary material: chapter 3). The updated data matrix contains now 228 characters, 65 in-group taxa (including Phoebodus and Thrinacodus) and one out-group taxon (Entelognathus). Phyloge-netic analyses were performed in TNT 1.5 (Tree Analysis Using New Technology [41]) via heuris-tic parsimony analysis (traditional search in TNT) using 10000 multiple random addition sequences. Swapping algorithm is tree bisection reconnection (TBR) with 10 trees saved per replication. For the nodal support, we resampled the data using 1000 bootstrap replicants (standard bootstrap and tra-ditional search options in TNT 1.5) and we per-formed Bremer support retaining trees suboptimal by 5 steps (Fig. S9).
3. Results
a) Genus and species diagnosis and description
For some of the material (PIMUZA/I 4656, 4710, 4712), we introduce the species Phoebodus said-selachus sp. nov. because it combines characters of previously known microremains such as mul-ticuspid body scales (Fig. S8), ctenacanthid fi n spines (resembling Amelacanthus sp., Fig. S6; [16]) and teeth intermediate between Phoebodus typicus [24] and Phoebodus politus [42]. Two specimens (PIMUZ A/I 4711, 4713) were deter-mined as Phoebodus sp. because they preserve neither diagnostic teeth nor fi n spines. The new fossils yield important novel anatomical informa-tion about Phoebodus concerning body parts such as the mandibular and branchial arches, shoulder girdle and neural arches (Fig. 1). Additionally, computer tomographs revealed details of the otic and occipital regions of the braincase, endocast and brachial arches (Fig. 2-3, S5). Using this ad-ditional anatomical data, we emend the genus di-agnosis of Phoebodus (previously based on teeth only).
The current genus defi nition of Phoebodus
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Figure 1. Phoebodus saidselachus sp. nov., (a – d) PIMUZ A/I 4712, (e) PIMUZA/I 4656. (a) ferruginous nodule containing cranial and postcranial remains; (b) drawing, scale bar = 200 mm; (c) detail of visceral skeleton, scale bar 100 mm; (d) tooth, scale bar = 5 mm (e) tooth in labial, aboral, baso-lateral and linguo-basal views, scale bar = 10 mm. adbc: anterior dorsal basal cartilage; bh, basihyal; cb, ceratobranchial; ch, ceratohyal; col, cololite; fs, fi n spine; mc, Meckel`s cartilage; mpt, metapterygium; n, neurocranium; na, neural arches; pdbc: posterior dorsal basal carti-lage; pq, palatoquadrate; rad, radials; sc, scapulacoracoid.
based on teeth [18] is as follows: crown with three long main cusps equally sized or median cusps slightly shorter; sigmoid outline of main cusps; intermediate cusplets absent or present, if present then short and thin; base is symmetric, extending lingually, a single orolingual button on lingual to-rus for articulation with the overlying tooth, arcu-ate basolabial projection; two openings for basal canal: one aborally and one lingually.
With the new material of Phoebodus (notes in electronic supplementary material), the follow-ing characters are now added to the genus defi -nition: Skeleton consisting of tesselate calcifi ed
cartilage, jaws amphystylic with tooth fi les sep-arated by gaps, multicuspid trunk scales; pharyn-geal teeth present; otico-occipital fi ssure present, two dorsal fi n spines with ctenacanthid ornamen-tation; dorsal fi ns with calcifi ed base plate; high supraoccipital crest; dorsal otic ridge forming crests posteriorly; elongate endolymphatic fossa; occipital arch deeply wedged between otic cap-sule; massive hypotic lamina; external opening for endolymphatic ducts anterior to a crus com-mune; elongate and narrow body (eel-like shape) and mandibular arches; long occipital region, ap-proximately 75 % of the otic length; ceratohyal anteriorly blade-shaped; otic process of the pala-
94
Chapter III: Phoebodontid Chondrichthyans of the Maider
Figure 2. Otic and occipital region of Phoebodus saidselachus sp. nov., PIMUZ A/I 4711, reconstructed on the basis of CT-scans: (a) anterior; (b) ventral; (c) dorsal; (d) lateral; (e) posterior view. Braincase and articulated branchial arches: (f) ventral view of braincase and ceratohyals, (g) anterior aspect of ceratohyal, (h) lateral view of ceratohyal, (i) dorsolateral view on hyomandibula-braincase articulation. Scale bars = 30 mm. Abbreviations: chy, ceratohyal; dor, dorsal otic ridge; endf, endolymphatic foramen; esc, external semicircular canal; fm, foramen magnum; glc, glossopharyngeal canal; hl, hypotic lamina; hym, hyomandibula; lda, lateral dorsal aorta; lof, lateral otic fossa; nc, notochordal canal; oc cot, occipital condyle; occr, occipital crest; psc, posterior semicircular canal; sac, sacculum.
toquadrate is dorsoventrally short.
The dentition of Phoebodus appears to be ho-modont. However, most teeth are broken and the diagnostic tooth bases are usually poorly visible, hard to prepare or lack resolution in the CT-imag-ery (Fig. S2c, S3c, S7). Therefore, we could not
verify if only one or several tooth forms [e.g. 18, 26, 28-29] are present in the jaws. The homodonty has to be confi rmed with further fi ndings or higher resolved tomographies in the future.
95
Chapter III: Phoebodontid Chondrichthyans of the Maider
Figure 3. Otic and occipital region of the endocast of Phoebodus saidselachus sp. nov., (PIMUZ A/I 4711): (a) dorsal, (b) ventral, (c) lateral, (d) anterior and (e) posterior views. Scale bar = 30 mm. Abbreviations: esc, external semicircu-lar canal; med, medulla; pa, posterior ampulla; psc, posterior semicircular canal; sac, sacculum; socc, spino-occipital.
b) Phylogenetic analyses
Our phylogenetic analyses are based on a matrix with 228 characters, 65 ingroup taxa and one out-group taxon (Entelognathus), which resulted in 720 most parsimonious trees of 543 steps. The strict consensus tree places Phoebodus and Thri-nacodus on the elasmobranch branch of the chon-drichthyan group (Fig. 4). Both taxa form part of a polytomy together with Cladodoides and the Ta-miobatis-xenacanth (Diplodoselache, Triodus and Orthacanthus) branch.
4. Discussion
(a) Phylogenetic relationships
Based on dental characters, it is widely accepted that thrinacodontids derived from phoebodontids during the Famennian [e.g., 18, 26]. The skeletal material of Phoebodus described here corrobo-rates the close phylogenetic relationship to Thr-inacodus. Both taxa are characterised by elon-gate body morphologies with long and slender heads including elongated mandibles with teeth with three main cusps of similar size. However, as already suggested by tooth morphology, Thr-inacodus is indeed more derived in some cranial and postcranial characters than Phoebodus. Thr-inacodus has a lower body height; in Thrinaco-dus, the body is only 20 mm high (body height to length ratio c. 0.02) while in Phoebodus it is 140 mm high (body height to length ratio c. 0.13), i.e.
almost one order of magnitude higher in propor-tions. The dorsal fi ns as well as their fi n spines are completely reduced in Thrinacodus [19; Fig. 5]. They also differ in the shape of their palatoquad-rates; the quadrate region is higher in Thrinaco-dus and offers a larger attachment surface for the adductor muscles. In contrast to Thrinacodus, the palatoquadrate as well as Meckel`s cartilage are elongated in Phoebodus. More differences be-tween Thrinacodus and Phoebodus are present in their visceral skeletons. From Thrinacodus, hy-pohyals and a simple rod-shaped ceratohyal was described by Grogan and Lund [19: Fig. 10C]. Remarkably, the branchial skeleton of Phoebodus challenges previous interpretations of phoebodon-tid branchial anatomy: In Phoebodus, the derived blade-shaped ceratohyal articulates anteriorly directly to the basihyal and hypohals are absent (Fig. 1a, b, 2f-h). Due to the imperfect preserva-tion in Phoebodus, pectoral, pelvic and caudal fi ns cannot be compared adequately between the two phoebodontids and thus hamper the discussion of differences in locomotion and manoeuvrability.
Our phylogenetic analyses revealed that Phoebodus is a stem elasmobranch. In the clado-gram (strict consenus tree in Fig. 4), this genus is situated in a polytomy together with Clado-doides, Tamiobatis-xenacanthids branch and hy-bodontids. Phoebodus, Tamiobatis, Orthacanthus and Tristychius share characters in the braincase such as the elongated endolymphatic fossa later-ally fl anked by prominent dorsal otic ridges [Fig. 2a-e; 6, 43, 44]. Moreover, a prominent supraoc-cipital crest is a common feature in Phoebodus,
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Entelognathus
Youngolepis
Guiyu
Psarolepis
Cheirolepis
Mimipiscis
Raynerius
Moythomasia
Culmacanthus
Ischnacanthus
Nerepisacanthus
Poracanthodes
Tetanopsyrus
Uraniacanthus
Diplacanthus
Rhadinacanthus
Cassidiceps
Mesacanthus
Promesacanthus
Cheiracanthus
Acanthodes
Homalacanthus
Halimacanthodes
Gladbachus
Brachyacanthus
Brochoadmones
Climatius
Parexus
Ptomacanthus
V waynensis
Gyracanthides
Latviacanthus
Pucapampella
Kathemacanthus
Lupopsyrus
Obtusacanthus
Doliodus
Acronemus
Egertonodus
Hamiltonichthys
Onychoselache
Tribodus
Squalus
Synechodus
Tristychius
Homalodontus
Cladodoides
Phoebodus
Thrinacodus
Diplodoselache
Orthacanthus
Triodus
Tamiobatis
Dwykaselachus
Ozarcus
Cladoselache
Cobelodus
Akmonistion
Damocles
Falcatus
Debeerius
Chimaeroidei
Chondrenchelys
Helodus
Iniopera
Kawichthys
Fig
ure 4
. Cladogram
(strict consensus tree) showing the placem
ent of Phoebodus and T
hrinacodus within the elasm
obranchs. Colour coding: black, stem
group gnathostome (out-
group); green, Osteichthyes; red, A
canthodii (stem C
hondrichthyes); orange, stem C
hondrichthyes excluding Acanthodii; blue, E
lasmobranchii (crow
n Chondrichthyes); purple,
Holocephali (crow
n Chondrichthyes). W
hite circles: bootstrap support of knot > 50%
and/ or Brem
er decay values > 1; black circles: bootstrap support >
75% and/or B
remer decay
values > 3.
97
Chapter III: Phoebodontid Chondrichthyans of the Maider
Figure 5. Possible body reconstruction of (a) Phoebodus saidselachus sp. nov., Late Devonian, (b) Thrinacodus gracia (Grogan & Lund, 2008), Early Carboniferous, and (c) picture of Chlamydoselachus anguineus Garman, 1884, Recent.
Tristychius, and xenacanthids [Fig. 2a, e; 6, 44]. In both Tristychius and Phoebodus, the dorsal and occipital crests are arranged similarly relative to each other and the ceratohyal that anterolaterally expands forming a medially directed blade (Fig. 2g,h). However, the semicircular canals form a crus commune unlike in Tristychius, which indi-cates that Phoebodus did not have any phonore-ception. Moreover, the arrangement of the semi-circular canals and the massive hypotic lamina with two openings for the lateral aortae in com-bination with the large diameter of the occipital condyle are characters shared with Cladodoides and Orthacanthus [9,44]. Compared to other ear-ly groups of elasmobranchs, phoebodontid elas-mobranchs have a very elongate occipital region (Phoebodus: Fig. 1B, S4; Thrinacodus: see [19]:
?occipital elements in fi g. 10C, 12C). The low otic process on the palatoquadrate (Fig. 1c) separates Phoebodus from all other early elasmobranchs.
The phylogenetic results corroborate the pro-posed close relationship between phoebodontid and xenacanthid taxa based on tooth morphology [18,45]. However, more morphological data of phoebodontids is necessary to get a better reso-lution of the phylogenetic relationship between these two groups.
(b) Palaeoecology
The skeletal material of Phoebodus was found in the Maïder basin, which is a small epicontinental
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Chapter III: Phoebodontid Chondrichthyans of the Maider
marine basin at the southern margin of the Palae-otethys [46-50]. Rough estimation of the palae-odepth of the Maïder basin suggested depths of maximally 400 meters in the depocentre and about 100 to 300 m at Madene el Mrakib [51]. Teeth of Phoebodus were mainly found in localities where moderately deep to moderately shallow water conditions prevailed during the Late Devonian; this taxon was proposed to live in the middle parts of the water column [18]. This coincides with the environmental conditions of the Maïder basin, where hypoxic to dysoxic conditions occurred repeatedly at the sea fl oor during the Famennian [32]; therefore, benthic life was rare and its diver-sity was correspondingly low in this region during much of the Famennian.
Among early chondrichthyans, phoebodon-tids are the fi rst taxa with an anguilliform body. Permian xenacanthid elasmobranchs also have a rather eel-like body but with several differences in anatomy [52-55]. Therefore, the discovery of skeletons of phoebodontids shows that the mor-phological disparity and ecological diversity of Devonian chondrichthyans was higher than pre-viously assumed.
The anguilliform body of phoebodontids is remarkably similar to that of the very distantly related modern neoselachian Chlamydoselachus. The length-to-height proportion of the body rather resembles Phoebodus, while dorsal fi n spines and dorsal fi ns are absent as in Thrinacodus except for a small second dorsal fi n in Chlamydoselachus. Because of these similarities in morphology and the absence of calcifi ed vertebrae centrae, we sug-gest that undulation was the mode of locomotion in phoebodontids (likely representing the plesio-morphic state of stem elasmobranchs).
The quadrate region of the palatoquadrate of both Phoebodus and Chlamydoselachus is dor-soventrally only slightly higher than the palatine ramus (Fig. 1a-c). Related to the function of the jaws, this implies that the surface for the attach-ment of the adductor muscle is reduced and that the bite was probably weaker than in other Palae-ozoic (e.g., xenacanthids, symmoriids) and mod-ern chondrichthyans.
Due to the similarities in body outline and tooth shape, Phoebodus probably pursued a feed-ing strategy comparable to chlamydoselachids al-though it is still unknown how the slow moving chlamydoselachids are capable of catching prey. Ram-feeding or lurking in combination with sud-denly snatching the prey are proposed feeding
behaviours [56, 57]. Because of the grasping den-tition of Phoebodus, they were unable to cut prey and only prey much smaller than their own body (which they could swallow whole) is feasible. Ad-ditionally, the morphology of the ceratohyal may inform about feeding mechanisms. Similarly to the ceratohyals of hybodontid Tristychius, those of Phoebodus are large and broad with a medial-ly directed anterior blade. Therefore, Phoebodus might have been a suction-feeder like hybodonts.
Stomach contents of phoebodontids were only found in Thrinacodus so far and they include remains of small chondrichthyans (Falcatus falca-tus [58], Harpagofututor volsellorhinus [59]) and crustaceans [19]. In recent frilled sharks, epipe-lagic squids, scyliorhinid and squaloid sharks [57, 60] were reported as stomach content. Possible prey for Phoebodus could have been thylacoceph-alan arthropods, which occur in great numbers in the host rocks of the Moroccan phoebodontids [32].
(c) Macroevolutionary implications
Based on the identifi cation of phoebodontids as stem elasmobranchs, an important macroevolu-tionary trend is emphasized. Generally, the Han-genberg Crisis is interpreted as a phase of a major turnover among vertebrates forming a bottleneck in their evolutionary history [61,62]. The pattern for Actinopterygii indicates a low diversity and disparity in the Devonian followed by an increase of morphological and taxonomic diversity after the Hangenberg Event [63]. Our new data about phoebodontids and thus the earliest anguiliform chondrichthyans emphasizes the morphological and taxonomic diversity of stem elasmobranchs during the Devonian. Remains of phoebodontids were reported from the Givetian (Middle Devo-nian; [18, 23]), which shows that stem elasmo-branchs were probably ecologically diverse long before the Hangenberg Event. This suggested disparate pattern for stem elasmobranchs and stem actinopterygians needs further analyses of the comparative anatomy of organ systems, their functional morphology and ecological interpreta-tion.
4. Conclusions
The fi rst anatomical information of the very com-mon genus Phoebodus based on the new species Ph. saidselachus sp. nov. in combination with the
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Chapter III: Phoebodontid Chondrichthyans of the Maider
knowledge of Thrinacodus gracia revealed that phoebodontids are anguiliform chondrichthyans. Our phylogenetic analyses show that phoebodon-tids are good candidates as the earliest stem elas-mobranchs exhibiting elongate bodies. Including the fact that the oldest phoebodontid remains are of Givetian age, this indicates that the root of stem elasmobranch diversifi cation temporally took place far back in the evolutionary history of chondrichthyans.
Author contributions: C.K, M. R., M.C and L.F.: developing the project; C.K, M. R. and L.F: fi eld work; I. J.: acquisition of computer tomogra-phy scans; M.G and V. H. determination of tooth material; M.C. and L.F: interpretation of fossils and 3D-models; phylogenetic analysis. L.F. illus-trations, anatomical reconstruction, drafting man-uscript.
Competing interests: The authors declare no competing interests.
Funding: The project (project number S-74602-11-01) was fi nancially supported by the Swiss Na-tional Fond. . M.R. was supported by NWO (VIDI 864.14.009).
Data accessibility: In preparation.
Acknowledgments: We greatly appreciate the help of Saïd Oukherbouch (Tafraoute, Morocco) who supported us during fi eld work and discov-ered some of the main specimens. We acknowl-edge Ben Pabst (Aathal) and Christina Brühwiler (University of Zurich) for their excellent prepara-tion work. Moreover, we thank Anita Schweizer (Zurich), Alexandra Wegmann (University of Zu-rich) for the acquisition of CT-scans. Many thanks to Thodoris Argyriou (University of Zurich), To-bias Reich (University of Zurich) and Amane Ta-jika (NHM of New York) for CT-scanning and help with segmentation. Gabriel Aguirre kindly helped with the phylogenetic analyses. We thank René Kindlimann (Aathal) for the very fruitful discussions and inputs.
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38. Burrow CJ, den Blaauwen J, Newman M, David-son R. 2016 The diplacanthid fi shes (Acanthodii, Diplacanthiformes, Diplacanthidae) from the Mid-dle Devonian of Scotland. Palaeontol. Electron. 19, 1-83.
39. Zhu M, Yu X, Ahlberg PE, Choo B, Lu J, Qiao QL, Zhao J, Blom H, Zhu Y. 2013 A Silurian placoderm with osteichthyan-like marginal jaw bones. Nature 502, 188-193. (doi:10.1038/nature12617)
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41. Goloboff PA, Catalano SA. 2016 TNT version 1.5, including a full implementation of phylogenetic morphometrics. Cladistics 32, 221-238.
42. Newberry JS. 1889 The Paleozoic fi shes of North America, Monograph of the U.S. Geological Sur-vey 16, 1-340.
43. Williams ME. 1998 A new specimen of Tamiobatis vetustus (Chondrichthyes, Ctenacanthoidea) from the Late Devonian Cleveland Shale of Ohio. J. Vert. Paleontol. 18(2), 251-260.
44. Schaeffer B. 1981 The xenacanths shark neurocra-nium, with comments on elasmobranch monophy-ly. Bull. Am. Mus. Nat. Hist.169, 1-66.
45. Ginter M. 2004 Devonian sharks and the origin of Xenacanthiformes. In Recent advances in the ori-gin and early radiation of vertebrates (eds. G Ar-
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ratia, MVH Wilson, R Cloutier). p. 473-486. Mün-chen, Friedrich Pfeil.
46. Wendt J. 1985 Disintegration of the continental margin of northwestern Gondwana: Late Devonian of the eastern Anti-Atlas (Morocco). Geology 13, 815-818.
47. Wendt J.1995 Shell directions as a tool in palae-ocurrent analysis. Sediment. Geol. 95, 161-186.
48. Wendt J, Kaufmann B, Belka Z, Klug C, Lubeseder S. 2006 Sedimentary evolution of a Palaeozoic ba-sin and ridge system: the Middle and Upper Devo-nian of the Ahnet and Mouydir (Algerian Sahara). Geol. Mag. 143(3), 269-299.
49. Fröhlich S. 2004 Evolution of a Devonian carbon-ate shelf at the northern margin of Gondwana (Jebel Rheris,eastern Anti-Atlas, Morocco). Unpublished PhD Thesis, University of Tübingen, Germany.
50. Lubeseder S, Rath J, Rücklin M, Messbacher R. 2010 Controls on Devonian hemi-pelagic lime-stone deposition analyzed on cephalopod ridge to slope sections, Eastern Anti-Atlas, Morocco. Fa-cies 56, 295-315.
51. Tessitore L, Naglik C, De Baets K, Galfetti T, and Klug C. 2016 Neptunian dykes in the Devonian carbonate buildup Aferdou El Mrakib (eastern An-ti-Atlas, Morocco) and implications for its growth. Neues Jahrb. Geol. Paläontol. Abhl. 281(3), 247-266.
52. Heidtke UHJ. 1982 Der Xenacanthide Orthacant-hus senckenbergianus aus dem pfälzischen Rotlie-genden (Unter-Perm). Pollichia 70, 65-86.
53. Heidtke UHJ. 1999 Orthacanthus (Lebachacant-hus) senckenbergianus Fritsch 1889 (Xenacanthi-da: Chondrichthyes): revision, organisation und phylogenie. Freiberger Forschungsheft 481, 63-106.
54. Heidtke UHJ, Schwind C. 2004 Über die Organisa-tion des Skelettes der Gattung Xenacanthus (Elas-mobranchii: Xenacanthida) aus dem Unterperm des südwestdeutschen Saar-Nahe-Beckens. Neues Jahrb. Geol. Paläontol. Abhl. 231(1), 85-117.
55. Heidtke UHJ, Schwind C, Krätschmer K. 2004 Über die Organisation des Skelettes und die ver-wandschaftlichen Beziehungen der Gattung Trio-dus Jordan 1849 (Elasmobranchii: Xenacanthida). Mainzer geowiss. Mitt. 32, 9-54.
56. Smith BG. 1937 The Anatomy of the Frilled Shark, Chlamydoselachus anguineus Garman. Bashford Dean Memorial Volume: Archaic Fishes Article 6, 333-506. American Museum of Natural History, N.Y.
57. Ebert DA, Compagno LJV. 2009 Chlamydosela-chus africana, a new species of frilled shark from southern Africa (Chondrichthyes, Hexanchiformes, Chlamydoselachidae). Zootaxa 2173, 1-18.
58. Lund R. 1985 The morphology of Falcatus falcatus St. John & Worthen, a Mississippian stethacanthid chondrichthyan from the Bear Gulch Limestone of Montana. J. Vert. Paleontol. 5, 1-19.
59. Lund R. 1982 Harpagofututor volsellorhinus new genus and species (Chondrichthyes, Chondrenche-lyiformes) from the Namurian Bear Gulch Lime-stone, Chondrenchelys problematica Traquair (Visean), and their sexual dimorphism. J. Vert. Pa-leontol. 56, 938-958.
60. Kubota T, Shiobara Y, Kubodera, T. 1991 Food habits of the Frilled Shark Chlamydoselachus an-guineus Collected from Suruga Bay, Central Japan. Nippon Suisan Gakk. 57(1), 15-20.
61. Sallan LC, Coates MI. 2010 End Devonian ex-tinction and a bottleneck in the early evolution of modern jawed vertebrates. Proc. Natl. Acad. Sci. 107(22), 1013110135.
62. Friedman M, Sallan LC. 2012 Five hundred mil-lion years of extinction and recovery: a Phanerozo-ic survey of large-scale diversity patterns in fi shes. Palaeontology, 55(4), 707-742.
63. Giles S, Xu GH, Near TJ, Friedman M. 2017 Early members of ‘living fossil’lineage imply later origin of modern ray-fi nned fi shes. Nature, 549(7671), 265.
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Fig. S1. Geological map of the southeastern Anti-Atlas of Morocco. The Thylacocephalan Layer with gnathostomes crops out in the Maïder region. Remains of Phoebodus were collected from the Famennian (Late Devonian) of Madene (30°44`407`` N, 4°42`899``W; 30°47`188`` N, 004°40`965`` W).
SUPPLEMENTARY FIGURES
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Fig. S2. Phoebodus saidselachus sp. nov. (PIMUZ A/I 4659), neurocranium and jaw fragments with mandibular teeth. (a) dorsal and (b) lateral aspects, scale bar = 100 mm. (c) ventral aspect of the anterior part of the snout and jaws with exposed tooth families, scale bar = 50 mm. j. frag, jaw fragments; n, neurocranium; pq, palatoquadrate; ros, rostrum; t, teeth.
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Fig. S3. Phoebodus saidselachus sp. nov. (PIMUZ A/I 4710), Meckel`s cartilages (mc) with intact anterior tooth whorls in situ (t). (a) ventral view, scale bar =100 mm. (b) detail and (c) drawing of the at least six most anterior tooth families of the right ramus of the lower jaw, scale bar = 10 mm. mc, Meckel`s cartilage; t, teeth.
Fig. S4. Braincase of Phoebodus sp. (PIMUZ A/I 4713). (a) Weathered specimen and (b) illustration in dorsal view; scale bar = 100 mm. asc, anterior semicircular canal; end.d, endolymphatic ducts; end.f, endolymphatic fossa; into, interorbital space; occ, occipital cotylus; psc, posterior semicircular canal; pop, postorbital process; soc, spino-oc-cipital canal.
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Fig. S5. Reconstructed braincase, mandibular and visceral arches of Phoebodus sp. (PIMUZ A/I 4711): (a) anterior, (b) posterior, (c) lateral, (e) dorsal and (f) ventral view. Colour coding: grey, braincase; orange, ceratohyal; blue, hy-omandibulare; turquoise, palatoquadrate; yellow, Meckel`s cartilage; light blue, fragments of ?epibranchials; purple, branchial elements; red, ?ceratobranchial; green, part of ?palatoquadrate.
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Fig. S6. Phoebodus saidselachus sp. nov. (PIMUZ A/I 4712), dorsal fi n spines. Lateral view of (a) anterior and (b) posterior dorsal fi n spines, scale bar = 50 mm. (c) detail showing ctenacanthid ornamentation, scale bar = 10 mm.
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Fig. S7. Phoebodus saidselachus sp. nov. (PIMUZ A/I 4712), mandibular teeth. Photo of the dentition with explana-tory drawing (a); scale bar = 10 mm. (b - e) detail of the dentition, photo with explanatory drawing, (b,c) oral views of teeth, (d) teeth in aborolateral view, (e) lateral cross-section of teeth in a row. Scale bars in (b-e) = 5 mm.
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Chapter III: Phoebodontid Chondrichthyans of the Maider
Fig. S8. Scales in the cranial region of Phoebodus sp. (PIMUZ A/I 4713). Scale bar = 5 mm.
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Chapter III: Phoebodontid Chondrichthyans of the Maider
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110
Chapter III: Phoebodontid chondrichthyans of the Maider
SUPPLEMENTARY NOTES
1) Devonian gnathostomes of Morocco
Morocco is famous for its often highly fossiliferous Devonian outcrops, which bear sometimes abundant invertebrates but also, somewhat rarer, inarticulated as well as articulated remains of vertebrates. Concern-ing vertebrates, macro- and microremains of placoderms and sarcopterygians are locally abundant in some strata and they were repeatedly reported from the Tafi lalt and Maïder regions of the southeastern Anti-Atlas (Lehmann 1956, 1964, 1976, 1977, 1978; Lelièvre & Janvier 1986, 1988; Lelièvre et al. 1993; Rücklin 2010, 2011; Rücklin et al. 2015, Rücklin & Clément 2017). Many taxa of Devonian chondrichthyans (e.g. Jalodus, Thrinacodus, Phoebodus, Ctenacanthus, Stethacanthus, Symmorium, Cobelodus, Denaea, Oro-dus, Protacrodus, Siamodus, Clairina) are documented by abundant isolated teeth and fi n spines, while cartilaginous structures such as a jaw were documented only once thus far (Lehman 1976; Derycke, 1992; Hampe et al. 2004; Derycke et al. 2008; Ginter et al. 2002; Derycke 2017). Only recently, more or less complete skeletons and braincases of chondrichthyans were found in the southern Maïder Basin (Fig. S1). The skeletal remains are preserved in ferruginous clayey nodules of reddish color found in the early/ mid-dle Famennian Thylacocephalan Layer in which thylacocephalans are highly abundant (Frey et al. 2018). Phoebodus is accompanied by numerous haematitic internal molds of cephalopods and phosphatised thyla-cocephalan as well as a few benthic invertebrates (Buchiola, Guerichia, ostracods and brachiopods). Con-cerning other gnathostomes, several species of well-preserved placoderms, sarcopterygians and cladodont chondrichthyans were found in and above the Thylacocephalan Layer. The palaeoenvironment at Madene el Mrakib was, during much of the Famennian stage, characterized by well-oxagenated waters in much of the water column while deeper water levels near the sea fl oor were oxygen-depleted, as inferred from the scarcity and low diversity of benthic invertebrates and the absence of bottom dwelling vertebrates (Frey et al. 2018). Taxa of invertebrates and vertebrates inhabiting higher water levels were more common and diverse, thus suggesting a better oxygenated water column.
2) Systematic Paleontology and specimen description
Class Chondrichthyes Huxley, 1880B
Subclass Elasmobranchii Bonaparte, 1838B
Family Phoebodontidae Williams in Zangerl, 1981
Included genera – Phoebodus St. John & Worthen, 1875A; Thrinacodus St. John & Worthen, 1875A; tentatively Diademodus Harris, 1951.
Family defi nition – Multicuspid teeth; three long main cusps intercalated by two small intermediate cus-plets; main cusps are sigmoidal; modestly ornamented cusps showing subparallel cristae; basis with lingual torus containing a single button for articulation; arcuate basolabial projection.
Remarks – The family Phoebodontidae includes the genera Diademodus, Phoebodus and Thrinacodus. While Phoebodus was only known from teeth for a long time, skeletal remains of Diademodus hydei Harris, 1951were found in the Devonian Cleveland Shales of Ohio, USA and complete skeletons of Thri-nacodus gracia (Grogan & Lund, 2008) were described from the Carboniferous of Bear Gulch, Montana. However, the inclusion of Diademodus in the Phoebodontidae is arguable as its teeth show multiple small cusps in contrast to the three large main cusps in Phoebodus (Ginter et al. 2010). Thrinacodus was as-signed to the family Thrinacodontidae by Grogan & Lund (2008) due to differences in tooth and base shape compared to Phoebodus. However, the differences are too weak to keep Thrinacodus in a separate family and therefore, it was suggested to place Thrinacodus together with Phoebodus within the Phoebodontidae (Long 1990; Ginter & Turner 2010).
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Chapter III: Phoebodontid chondrichthyans of the Maider
Genus Phoebodus St. John & Worthen, 1875A
Type species – Bathycheilodus macisaacsi St. John & Worthen, 1875A, later named Phoebodus macisaa-csi Wells, 1944C and fi nally Phoebodus sophiae Ginter et al., 2010.
Stratigraphical and geographical distribution– Givetian to Famennian; nearly cosmopolitan.
Diagnosis – emended genus diagnosis, see main article.
Phoebodus saidselachus sp. nov.
Holotype – PIMUZ A/I 4712
Stratigraphic and geographic occurrences – early to middle Famennian of the Madene (30°44`407`` N, 4°42`899``W) and Aguelmous, Maïder region, Anti-Atlas, Morocco.
Material – One nodule with cranial and postcranial material (PIMUZ A/I 4712) and two braincases (PIMUZA/I 4656, PIMUZ A/I 4710).
Derivation of name – After Said Oukherbouch (Tafraoute), the fi rst name of our Moroccan collaborator in the fi eld (the Arabic word ديعس means ‘happy’), and the Latin word selachus (shark).
1. Specimen PIMUZA/I 4656 and PIMUZ A/I 4710
Mandibular dentition and tooth morphology – Several mandibular tooth fi les are exposed in specimen PIMUZ A/I 4656 and PIMUZ A/I 4710 (Fig. S2c; S3b-c). The teeth are weathered, very soft and encrusted by a hard ferruginous layer. Removing these crusts by preparation results in destruction of the fossil ma-terial with its structure. Therefore, very little of the fi ner morphological details is visible. PIMUZ A/I 4656 bears six, probably seven tooth fi les separated by gaps in the anterior parts of the upper jaws and in PIMUZ A/I 4710, six tooth fi les are countable in the anterior region of the lower jaws.
Tooth fi les 1 to 3 of the upper left and fi les 1 to 2 of the upper right jaw in PIMUZ A/I 4656 contain three teeth, which are exposed from mostly labial and orolabial aspects (Fig. S2c). In PIMUZ A/I 4710, between two and six teeth are countable within the tooth fi les and several views are exposed (1A-D: labial; 2B: aborolabial; 3A-B: lingual; 4A-F: aboral and orolateral; 5A-C:?; 6A-B: oral and labial; Fig. S3b,c). PIMUZ A/I 4656 shows a single tooth that is well-preserved and which is exposed from labial, lateral and oral sides (Fig. S2c: tooth 4A; Fig. 1e). Labially, there is a large median cusp and two large lateral cusps of nearly identical length, but the lateral cusps appear to be more massive and broader in diameter than the median cusp (Fig. 1e). All main cusps are lingually recurved and show a sigmoid outline in lateral view. Between the large central and lateral cusps, there are two minute intermediate cusplets reaching maximally half of the length and thickness of the central cusp. Each main cusp shows an ornamentation consisting of two distinct striae forming rather sharp edges. The tooth base is squarish with rounded angles in ab-oral view and is 5.2 mm wide and 4.5 mm long. From labial, aboral and lateral aspects, the base shows a concave outline. The basolabial projection is wider than the median cusp and consists of a labiolingually narrow and slightly arcuate prominence. A large aboral foramen of the main basal canal lays lingually to the basolabial projection. In PIMUZ A/I 4710, a single tooth (Fig. S3b-c, 2b) with a well-preserved base of the same morphology is present, which shows that the two specimens are conspecifi c.
The dentition of Phoebodus saidselachus sp. nov. is homodont when size and shape of all preserved teeth are compared among each other. Size appears to differ hardly among teeth of the same tooth fi le, but this might be a view biased by the insuffi cient preservation or exposure of only parts of each tooth whorl. Grogan & Lund (2008) reported a homodont dentition from Thrinacodus gracia, while Ginter & Turner (2010) described a minor heterodonty (teeth between lower and upper jaw and between anterior and poste-rior positions differ in size and symmetry) based on unarticulated teeth of Thrinacodus ferox.
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Chapter III: Phoebodontid chondrichthyans of the Maider
Neurocranium and mandibular arches - Neurocranial and mandibular remains of Phoebodus saidse-lachus sp. nov. are three-dimensionally preserved but embedded in ferruginous rocks or covered by fer-ruginous crusts and therefore, anatomical details are hardly exposed. Internal structures of the braincase are recognizable in some cross-sections. Computer tomography scanning and neutron scanning resulted in image stacks of insuffi cient contrast because of hydroxyl-rich compounds in the host rocks. Thus, the morphology of the cranial region of the specimens is here described only superfi cially.
In PIMUZ A/I 4656, a ferruginous crust revealed the outline of the braincase, palatoquadrates and Meckel`s cartilages (the rock containing all these elements measures 0.33 m in length). In dorsal and ventral view, the skull becomes increasingly slender from posterior to anterior and anteriorly ends in a rounded and somewhat blunt snout that is much less pointed than in Thrinacodus gracia (Fig. S2a, c). The overall shape of the skull is elongated and slender compared to most Palaeozoic chondrichthyans but less slender than in the more derived phoebodont Thrinacodus gracia. Laterally, fragments of the long jaws are present that fl ank the entire specimen (Fig. S2b, c). In PIMUZ A/I 4710, parts of both Meckel`s cartilages are exposed and show no symphysial fusion anteriorly, which is the common condition in Palaeozoic chon-drichthyans (Fig. S2c, S3a). Anterior to the lower jaws, teeth are present whose sizes are small compared to jaw dimensions. These proportions appear to correspond well with the reconstructions of Thrinacodus (Grogan & Lund, 2008).
Remarks - Quite a few species of Phoebodus based on teeth with almost identical crowns and only minor differences in the bases were described from the Famennian. These are: Ph. rayi (Ginter & Turner, 1999), Ph. typicus (Ginter & Ivanov, 1995), Ph. turnerae (Ginter & Ivanov, 1992), Ph. gothicus (Ginter, 1990), and Ph. politus (Newberry, 1889). Ph. rayi (Ginter & Turner, 1999) and Ph. turnerae (Ginter & Ivanov, 1992) can easily be removed from the comparison with Ph. saidselachus sp. nov., because their orolingual button is not situated in the centre of the base, but at the lingual rim. Most specimens of Ph. gothicus have much longer bases, which are lingually rounded or end with an angle. However, the teeth of Ph. typicus and Ph. politus are very similar to those of Ph. saidselachus sp. nov. and in fact, they can easily be confused among each other. Tooth bases of Ph. typicus are more rectangular and wider than in Ph. saidselachus sp. nov., while the tooth bases are more circular in Ph. politus. The published teeth of the latter species (New-berry 1889, pl. 27, fi gs 27, 28; Eastman 1907, pl. 7, fi g. 5; 1908, pl. 1, fi g. 9) are relatively large and about the same size as Ph. saidselachus sp. nov. (base width about 7-8 mm), whereas all the known teeth of Ph. typicus do not exceed 2 mm. As far as the tooth morphology is concerned, Ph. saidselachus sp. nov. is situated between the older species (Ph. typicus, early-middle Famennian) and the younger one (Ph. politus, late Famennian).
2. Specimen PIMUZ A/I 4712
Mandibular dentition and tooth morphology - Remains of small partially articulated teeth lie in the space between the right upper and lower jaw (Fig. 1a,c). All teeth are extremely fragile and it is not possi-ble to extract one without damaging it signifi cantly. The diagnostic morphological details of the tooth base is often not exposed or not preserved. However, some bases show a rounded outline lingually similar to specimen PIMUZA/I 4656 and PIMUZ A/I 4710. Therefore, we assign all three specimens to Phoebodus saidselachus sp. nov.
In labial aspects, the teeth show the characteristic crown shape of phoebodontids with three long main cusps (one median and two laterals) of similar length. In oral view, the cusps appear to recurve subtly lin-gually (Fig. S7c). Very faint traces of cross-sections of minute intermediate cusplets between the central and lateral cusps are present in two teeth (Fig. S7b,c). Cusp ornamentation is either not preserved or not present. In oral and aborolateral aspects, the preserved remains of the tooth bases show a rather subcircular or probably slightly rectangular outline. Lingually and close to the crown, a single orolingual button of oval shape is visible. This protrusion is wider than the central cusp and covers around half of the labiolin-gual length of the base (Fig. S7b). Posterior to the orolingual button, the lingual opening of the main basal canal is situated. In aborolateral view, the base shows remains of an elliptical concavity in the center, which serves as an articulation surface for the orolingual button of a former tooth (Fig. S7d). Cross-sections of lateral aspects of tightly packed teeth are visible in some jaw regions (Fig. S7a, e). The articulated teeth do
113
Chapter III: Phoebodontid chondrichthyans of the Maider
not differ measurably in size among each other. In lateral view, the base shows sometimes an aborolingual concavity, which fi ts to the orolingual convexity of the former tooth.
The preserved teeth let assume that the dentition of the described specimen of Phoebodus was homo-dont: its teeth do not signifi cantly differ in size or shape within or between jaw types. There are few teeth that look slightly different: the most posterior tooth (marked with an asterisk in Fig. S7a) appears to have a stouter crown with median and lateral cusps showing a wider diameter compared to the other teeth. A second tooth shows a much bigger base from the oral aspect (marked with asterisk in around the middle of Fig. S7a). However, mostly the crowns are exposed or preserved, which are less diagnostic on the species level than the tooth bases.
Body form and proportions - In PIMUZ A/I 4712, the right and left Meckel`s cartilage, the right pala-toquadrate, some parts of the branchial and postcranial skeleton (shoulder girdles, pelvic fi n remains, dorsal fi n spines, neural arches) and traces of the body outline are present (Fig. 1a,b). The caudal region is largely eroded. According to this specimen, Phoebodus had an elongated, anguilliform body shape similar to Thrinacodus, but less slender. The entire specimen measures 0.98 m from the preserved anterior edge of the jaws to the most posterior fragment of cartilage. However, this specimen was longer; based on the length of the nodule, which usually corresponds roughly to the shape of the incorporated carcass, we esti-mate that the complete animal was at least 1.2 m long. The jaws are long and delicate measuring 0.18 m, although the anterior ends of the jaws are missing. The distance between the anterior end of jaws to the fi rst dorsal fi n spine measure 0.38 m and the distance between the fi rst and second dorsal fi n spines is 0.4 m. The body height of Phoebodus is low but both relatively and absolutely higher than in Thrinacodus (only 20 mm high): In PIMUZ A/I 4712, the anterior part of the lower and upper jaws together is around 0.05 m high, the branchial arch region around 0.11 m and the thoracic region around 0.14 m high. Estimated body proportions are as follows: jaw length to body length maximal 15% (Thrinacodus: head length to body length 8.5%) and body height to body length maximal 11% (Thrinacodus: 3%).
Mandibular arches - The right and left Meckel`s cartilage (mc) as well as the right palatoquadrate (pq) are exposed from the lateral and slightly ventral view (Fig. 1c). Anteriorly, the tips of the lower jaws and palatine rami are missing. Estimation of the missing nodule part is approximately 50 mm in anteroposterior length. Like in Thrinacodus gracia, there are no traces of labial cartilages that are a common feature in hybodonts and recent chondrichthyans.
All jaw elements are elongated, which contrasts the mandibular conditions in many other Palaeozoic chondrichthyans (xenacanthids, cladoselachians, symmoriids and hybodontids). This morphological trait segregates Phoebodus from Heslerodus that was previously described as Ph. heslerorum (Zangerl 1981; Stahl 1988) and therefore supports the teeth-based revision of Ginter (2002). In contrast to Thrinacodus gracia, where the palatoquadrate is much shorter than Meckel`s cartilage, both upper and lower jaws are elongated to roughly the same extend in Phoebodus. In Ph. saidelachus sp. nov. (PIMUZ A/I 4656) de-scribed in this work, the upper jaw appears to reach some millimeters anterior of the lower jaw (Fig. S2c).
Both Meckel`s cartilages are exposed from lateral and slightly ventral aspects and show an anteriopos-teriorly elongation. The overall slender shape resembles the lower jaws of chlamydoselachids, xenacan-thids and Thrinacodus gracia. The posterior half is dorsoventrally about the same height as the quadrate re-gion of the palatoquadrate. Towards the anterior end of the nodule, Meckel`s cartilage is slightly narrowing dorsoventrally. Posteriorly, the dorsoventral outline thins out and forms an amphistylic articulation with the palatoquadrate. The dorsal edge of the right lower jaw is slightly concave anterior to the articulation; it is also rather straight along the rest of the jaw. Posteroventrally, the edge of the right jaw fl ips laterally forming a rim.
The ventral edge of the right palatoquadrate is covered anteriorly by teeth and posteriorly by Meckel`s cartilage. A little dorsal to the ventral edge and anterior to the articulation of the jaws, a prominent lateral ridge (80 mm long and 10 mm high) extends from the quadrate region and runs in parallels across two thirds of its anteroposterior length (Fig. 5, 7a-c; mcr). However, this ridge might have formed due to ta-phonomic alteration such as compcation. The quadrate region is dorsoventrally only slightly broader than the suborbital palatine, which differs from the condition in Thrinacodus gracia, the xenacanthids and the symmoriiforms. Similar conditions with a dorsoventrally relatively short quadrate region are known from
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recent Chlamydoselachus and hybodontids, although in latter one the quadrate region is laterally expanded forming a quadrate fl ange (Smith 1937; Maisey 1982, 1986). In Phoebodus, the posterodorsal edge of the quadrate region is fl ipped laterally, thus forming a strong posterolateral rim where the adductor muscles are inserted. The remains of the suborbital palatine ramus are slightly narrower dorsoventrally than the quadrate region.
Hyoid and gill arches - The basihyal (bh), a ceratohyal (ch) and two ceratobranchials (cb) are preserved (Fig. 1c). Additional branchial arches might be preserved, but they are hardly distinguishable from each other due to its mode of preservation. Branchial rays are either not present or not preserved and were also not described from Thrinacodus gracia (Grogan & Lund 2008).
A long triangular cartilage lies posterior to the point where the lower jaws meet. This cartilage proba-bly represents the basihyal in ventral aspect. A comparable structure was not described from Thrinacodus (Grogan & Lund 2008) but the position of the cartilage corresponds to the subtriangular anteriormost ba-sibranchial documented for Akmonistion and Stethacanthus (Coates & Sequeira 2001; Lund 1985a). Other basibranchial elements such as those described from Cobelodus (Zangerl & Case 1976) and Heslerodus (Williams 1985) were not found in Phoebodus.
The left ceratohyal articulates posteriorly to the basihyal and it parallels the left Meckel`s cartilage. It is exposed from its lateral aspect posteriorly and from the ventrolateral aspect anteriorly. The ceratohyal mea-sures between around 1/2 and 1/3 of the mandibular length and posteriorly, it curves to the same degree as the posteroventral edge of the left Meckel`s cartilage. It is rather straight in profi le compared its semicres-cent shape in symmoriids, cladoselachids (Coates & Sequeira 2001) and xenacanthids (Heidtke & Schwind 2004). Moreover, unlike in Akmonistion zangerli (Coates & Sequeira 2001), the ceratohyal of Phoebodus is not uniformly thick throughout its length: its posterior edge is dorsoventrally broad but towards the ante-rior end, the cartilage is narrowing. In ventral view, the ceratohyal is narrow over around 3/4 of its length, but in its anteriormost quarter, the ventral surface is laterally expanding and forms a fl ange (anteriorly blade-like shaped) articulating anteriorly with the basihyal. A similar medial fl ange is present in Tristychius arcuatus (unpublished information M. Coates). There is no hypohyal anterior to the ceratohyal such as it is present in Thrinacodus gracia and xenacanthids (Triodus and Xenacanthus; Heidtke et al. 2004).
Remains of ceratobranchials are preserved dorsal to the left ceratohyal. There is a rod-shaped rest of a ceratobranchial of slightly shorter length than the ceratohyal. Weak traces of two additional ceratobranchi-als are exposed above the relatively well-preserved ceratobranchial. Other elements such as epibranchials, hypobranchials and pharyngobranchials cannot be determined with certainty, although the body outline adumbrates the presence of more branchial elements.
Pectoral girdle and fi ns - The scapulacoracoid (sc) is partially preserved in PIMUZ A/I 4712. From the pectoral fi n, fragments of the metapterygium and remains of fi ve tightly packed radials (rad) or basals alike Thrinacodus are preserved (Fig. 1a, b). Dorsally, the scapula is broken and there is no information about anterodorsal and posterodorsal processes preserved. The scapula and coracoid are fused and their shape re-sembles the scapulacoracoids of symmoriids. The coracoid region is anteriorly convex and there is a broad ventral concavity probably serving as an articular surface for fi n radials. On the posterior edge of the cora-coid, there is a rather deep and small concavity; however, this concavity could be the result of taphonomic alteration. Coracoid plates separated from the scapula such as in Thrinacodus gracia (Grogan & Lund 2008) are absent in Phoebodus. Posterior to the coracoid, there are possible fragments of a metapterygium (mpt) that is articulated to fi ve poorly preserved radials.
Pelvic girdle and fi ns - On the ventral side of the specimen at the position of the second dorsal fi n spine, the nodule extends into a fi n-like protrusion, probably documenting the former presence of pelvic fi ns and their position (Fig. 1a, b). Below the second dorsal fi n spine, several remains of cartilage are visible. The different cartilages are hardly distinguishable from each other. Two of these cartilages may represent remains of radials (rad).
Dorsal fi n and fi n spines - Radials of dorsal fi ns are absent but faint traces of cartilage (adbc, pdbc, Fig. 1a,b) are located posterioventrally to both fi n spines. Probably, this cartilage was serving as a support for the fi n spine like the triangular basal elements in hybodonts (Maisey 1982). Two fi n spines are well exposed in association with the anterior and posterior dorsal fi ns (fs, Fig. 1a, b, Fig. S6a, b). Both spines
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Chapter III: Phoebodontid chondrichthyans of the Maider
are closely aligned to the body outline, but their orientation could have been altered taphonomically while their relative positions appear to correspond to their primary relative positions, at least with respect to their distance from each other. The anterior fi n spine is proximodistally longer and anteroposterioly thicker than the posterior one. The fi n spines are slender, slightly recurved, deeply inserted and in that respect resemble Sphenacanthus aquistriatus and Amelacanthus (Maisey 1982). Their edges are smooth and the dorsal edg-es of both fi n spines are slightly convex while the ventral spine wall is slightly sigmoidal in profi le (pos-teriorly, the last third of the spine length shows a subtle concavity). The ornamentation of the fi n spine is poorly visible because most of the spine surface is weathered. There still are some remains of ctenacanthid ornaments (Fig. S6c) consisting of regular costae intercalated by narrow intercostal grooves and transverse ridges interrupting the costae regularly, giving the ornament a zipper-like appearance.
Axial Skeleton - Ventral to the anterior dorsal fi n spine, remains of neural arches are discernible (Fig. 1a, b). Anteriorly, it is not possible to visually separate the neural arches from each other. Towards the posteri-or, the outlines of twelve neural arches of vertebrae become clearer. The dorsal edge of the closely packed, slender and rod-shaped neural arches are directed posteriorly. Among the preserved arches, the posterior arches are dorsoventrally longer than the more anterior ones forming a crest-like structure; it is not clear whether this might be due to a taphonomic alteration (e.g., compaction, collapse, etc.). Vertebral elements such as interventrals, basidorsals, basiventrals and hemal spines were described in Thrinacodus but these are not preserved in the Phoebodus specimen described here.
Remarks - In spite of its unique completeness, especially when compared to the previously known fossil record of Phoebodus consisting of countless teeth mainly, the preservation of the here described specimen is far from perfect. For example, the caudal fi n and much of both pelvic and pectoral fi ns are missing. This is quite characteristic for the taphonomy of the gnathostomes of the Thylacocephalan Layer in the southern Maïder (Frey et al. submitted). Usually, the fi sh remains are incorporated in large fl at nodules rich in hae-matite and limonite. The head and gill regions usually is encased in the thickest part of the nodule, while most of the postcranium lies on top of the nodule that thins out posteriorly. In some rare cases, the caudal fi n still rests on the nodule while in most other cases, the posterior of the skeletons is eroded, because it was embedded in the deeply weathered crumbling claystone. Nevertheless, the shape of the nodules very roughly traces the outline of the former carcass, thus documenting the overall body shape, position of fi ns and their rough dimensions. Based on this indirect evidence, we suggest that the caudal fi n resembled that of Thrinacodus in lacking strongly developed dorsal and ventral lobes as in, e.g., modern elasmobranchs like Carcharodon. Instead, the caudalis probably had a shape like that known from Thrinacodus (but less elongate) or Cladoselache.
Phoebodus sp.
Specimen PIMUZ A/I 4711 and PIMUZ A/I 4713
Neurocranium - In PIMUZ A/I 4713, the dorsal portion of the otic and occipital region and a small part of the interorbital space is preserved. In PIMUZ A/I 4711, computer tomographies provide anatomical insights into the otic region including semicircular canals and the entire occipit.
The preserved remains of the postorbital process indicate a short, anteroposteriorly narrow process (Fig. S4). In the otic region, the anterior and posterior semicircular canals dorsally unify to a crus commune such as in symmoriiforms, Cladodoides and xenacanthids. Therefore, Phoebodus likely had no for phono-reception. The endolymphatic chamber is narrow anteriorly and broadens dorsally; paired endolymphatic ducts are located anterior to the crus commune (Fig. S4). The endolymphatic fossa is narrow and laterally fl anked by prominent dorsal otic ridges (Fig. 2a-d, S5a-e), which closely resembles the condition seen in Tamiobatis, Orthacanthus, and Tristychius (Williams 1998; Schaeffer 1981; Coates & Tietjen 2018). This shape of the endolymphatic fossa is in contrast to the ovoid shape in Stethacanthus Newberry, 1889, Ak-monistion Coates & Sequeira, 2001 and Dwykaselachus Oelofsen, 1986. Similar to the condition in Clado-doides, the glossopharyngeal canals are fl oored by a massive hypotic lamina, which hosts two openings for the lateral dorsal aortae posteriorly (Fig. 2b). Therefore, the dorsal aorta splits posterior to the occipital
116
Chapter III: Phoebodontid chondrichthyans of the Maider
level like in Cladodoides, Tamiobatis, Tristychius and xenacanthids (Maisey 2005; Schaeffer 1981; Coates & Tietjen 2018).
The occipital region is elongated compared to other early and modern elasmobranchs but might be similarly elongated in the phoebodont Thrinacodus gracia (Fig. S4a-b; fi g. 10C in Grogan & Lund 2008). On the right lateral side of the occiput, traces of three canals for the spino-occipital nerves are preserved. Moreover, the prominent supraoccipital crest is a common feature of Phoebodus, Tristychius, and xenacan-thids (Schaeffer 1981; Coates & Tietjen 2018).
Branchial arches – Remains of hyoids articulate at the periotic region of the braincase (Fig. S5a, e). They are fl at, dorsoventrally broad and slightly curved. Anteriorly, the ceratohyals anteriorly have a fl ange like in PIMUZ A/I 4712 (Fig. 1c, 2i, S5a, e). Remains of mandibular and gill arches with little anatomical details are preserved (Fig. S5a-f): the palatoquadrate has fl ipped to the ventral side of the braincase and it has been recognized by the presence of the dorsal crest of the otic process (Fig. S5f).
Endocast – The reconstructed endocast (Fig. 3a-e) shows parts of the sacculum, the external and posterior semicircular canals, and the medulla. Like in symmoriids, xenacanthids and Cladodoides, the posterior semicircular canals form a wide arch each and unify with the posterior ampullae. The medulla of Phoebo-dus is anteroposteriorly long which resembles the condition in other elasmobranchs such as Cladodoides and xenacanthids (Maisey 2007; Schaeffer 1981).
Body squamation - Multicuspid scales are preserved in the head region of PIMUZ A/I 4713. Due to their poor preservation and because they are embedded in the host rock, a morphological description is impos-sible at this point (Fig. S8).
3) Taxa and sources
The taxa list was adopted from Coates et al. (2018). 22 taxa of stem gnathostomes (including Agnatha, Placodermi and some Osteichthyes) were excluded from the phylogenetic analyses as they were not rele-vant for the position of the phoebodontid chondrichthyans within the chondrichthyan phylogeny.
Acanthodes: Benznosov 2009; Brazeau & de Winter 2015; Coates 1994; Davis et al. 2012; Heidtke 1993, 2011a,b; Jarvik 1977, 1980; Miles 1968, 1973a, b; Nelson 1968; specimens AMNH 1037b, 10370, 10376, 19628; CMNH 30725b, 30726, 4591; FMNH PF2875; GM C145, 146, 180; HM V8251, 252; HU MB.F.4209, 4277, 4284, 4285, 7286, MB3b, 4a & b, 5a & b, 7a & b, 8a & b, 11a & b, 12a, 13a &b, 14a &b, 16a &b, 17a & b, 18a & b, 23 (resin copy), 24, MM L1693, 1698, 9432B, W1994; NHM P.11287, P.13139, 13140, 14558, 1728, 34912, 34914, 4057, 49941, 49944, 49959, 49967, 49979, 49980, 49990, 49995, 49996, 60928, 60939, 62138, 7335; NMS 2001.7.1, 3; UCL GM C1126; UMZC GN9, 11, 13, 14, 15a &b, 16, 39, 756.
Acronemus: Maisey 2011; Rieppel 1982.Akmonistion: Coates & Sequiera 1998, 2001a, b; Coates et al. 1998; Coates et al. 2017.Brachyacanthus: Denison 1979; Miles 1973a; Watson 1937; specimens NMS Kinnaird 88, NMS (Powrie)
1891.92.212, 213, 214, 220, 222, 224, 225, 226, 227.Brochoadmones: Bernacsek & Dineley 1977; Gagnier & Wilson 1996b; Hanke & Wilson 2006; specimens
UALVP 32672, 41487, 41493, 41494, 41495.Callorhinchus/Hydrolagus: Cole 1896; De Beer 1937; De Beer & Moy-Thomas 1935; Didier 1995; Didier
et al. 1994, 1998, 2012; Howard et al. 2013; Kesteven 1937; Patterson 1965, 1992; Pradel et al. 2013; Stahl 1999.
Cassidiceps: Gagnier & Wilson 1996a; specimen UALVP 32454.Cheiracanthus: Denison 1979; Miles 1973a; Watson 1937; specimens AMNH 317, 6929, 7082; GM C295,
296, 325, 490; HM V7614; IC 214, 215, 216, 217; UMZC GN14a &b, 19, 20, 21, 31, 50; 1131a & b, 1132a & b, 1133a & b, 1134a & b, 1135a & b, 1136a & b, 1137a & b, 1138, 1139, 1140.
Cheirolepis: Arratia & Cloutier 1996; Pearson & Westoll 1979; Giles et al. 2015a.Chondrenchelys: Finarelli & Coates 2012, 2014; Lund 1982; Moy-Thomas 1935; specimens NMS
1885.54.5/5A, 1891.53.33, 1998.35.1, 2002.68.1; BGS-GSE 13328; HM V.7173.
117
Chapter III: Phoebodontid chondrichthyans of the Maider
Cladodoides: Gross 1937, 1938; Maisey 2005.Cladoselache: Bendix-Almgreen 1975; Harris 1938a, b; Maisey 1989a, 2007; Schaeffer 1981; Williams
2001; Woodward & White 1938; specimens CMNH 8110, 8111, 8207, NHM P9273, P9285.Climatius: Miles 1973a, b; Watson 1937: specimens AMNH 7762; GSM 49785; MM L12096a & b; NMS
Kinnaird 80; NMS 1881.5.62; NMS 1887 (Peach) 35.3a, 35.5b, 35.5e; NMS 1891 (Powrie) 92.195, 204, 206, 214; NMS 1967.12.4; NMS 1973.9.4; NMS 2001.7.2.
Cobelodus: Zangerl & Case 1976; Zidek 1992.Culmacanthus: Long 1983.Damocles: Lund 1986: specimens CM 35472, 48760.Debeerius: Grogan & Lund 2000: specimens CM 35479, 35480, 48831, 62811.Diplacanthus: Gagnier 1996; Miles 1973a; Watson 1937; specimens FMNH PF11633; GM C12, 13, 148;
GM P482; MM L5503, 1609; NMS (Powrie) 1891.92.334; NMS 2001.7.4; UMZC GN17, 18, 22.Diplodoselache: Dick 1981.Doliodus: Miller et al. 2003; Maisey et al. 2009, 2013, 2017; Long et al. 2015.Dwykaselachus: Coates et al. 2017; Oelofsen 1986; specimen SAM K5840.Egertonodus: Maisey 1982, 1983; Lane, 2010.Entelognathus: Zhu et al. 2013.Falcatus: Lund 1985; Maisey 2007; specimens CM 35465, 37532Gladbachus: Heidtke & Krätschmer 2001; Heidtke 2009; Burrow & Turner 2013; specimen UMZC
2000.32.Guiyu: Zhu et al. 2009.Gyracanthides: Miles 1973a; Warren et al. 2000; Turner et al. 2005.Halimacanthodes: Burrow et al. 2012.Hamiltonichthys: Maisey 1989b.Helodus: Patterson 1965; Stahl 1999; specimens NHM P.6706, 8207, 8209, 8212, 8213.Homalacanthus: Gagnier 1996; Watson 1937; specimens FMNH PF4875; MM LL12452.Homalodontus: Mutter et al. 2007, 2008.Iniopera: Zangerl & Case 1973; Pradel et al. 2009, Pradel 2010; Pradel et al. 2010.Ischnacanthus; Miles 1973a; Watson 1937; specimens GM C3, 6, 149, 324; GM P298; MM L9522, 9431,
9432; MM STR0585; NMS (Powrie) 92.254, 258; UALVP 32401, 32405, 32414, 39060, 39075, 40478, 41491, 41861, 42201, 42215, 42660, 43245, 44048, 44049, 44091, 45014.
Kathemacanthus: Gagnier & Wilson 1996a; Hanke & Wilson 2010; specimens UALVP 32402, 42269, 43113.
Kawichthys: Pradel et al. 2011.Latviacanthus: Schultze & Zidek 1982.Lupopsyrus: Hanke & Davis 2012; Bernacsek & Dineley 1977; specimens NMC 22700B, 22700C, 22715,
22718, 22719, 22700D, 22700E, 22700F, 22701C, 22701D, 22716, 22717, 22720, 22745; UALVP 19260, 32420, 32442, 32456, 32458, 32474, 32476, 32480, 32482, 39065, 39067, 39079, 39080, 39081, 39082, 39121, 41493, 41629, 41632, 41665, 41931, 41939, 41945, 42000, 42002, 42008, 42012, 42013, 42027, 42046, 42061, 42113, 42142, 42150, 42173, 42208, 42274, 42518, 42524, 42529, 42530, 42533, 42538, 42453, 42454, 42455, 42544, 42597, 42605, 43064, 43091, 43092, 43094, 43095, 43256, 43409, 43456, 45154, 45155.
Mesacanthus: Miles 1973a; Watson 1937; specimens FMNH PF1439; GM C18, 288a &b; NMS (Powrie) 1891.92.275; UMZC GN1143.
Mimipiscis: Gardiner & Bartram 1977; Gardiner 1984; Choo 2011; Giles & Friedman 2014.Moythomasia: Gardiner & Bartram 1977; Gardiner 1984; Coates et al. 2017; specimen MV P222915.Nerepisacanthus: Burrow 2011; Burrow et al. 2014.Obtusacanthus: Hanke & Wilson 2004; specimen UALVP 41488.Onychoselache: Dick & Maisey 1980; Coates & Gess 2007.Orthacanthus: Heidtke 1982, 1999; Hotton 1952; Schaeffer 1981; Maisey 1983; Lane & Maisey 2009.Ozarcus and FMNH PF 13242: Maisey 2007; Pradel et al. 2014; Coates et al. 2017.Parexus: Watson 1937; Miles 1973a. specimens AMNH 1163, 7766; NMS Kinnaird 94; NMS (Peach)
1887.35.3a, 5e; NMS 1891 (Powrie) 92.183, 184, 186, 188, 194, 197, 207; NMS 1956.14.4.15; NMS 1977.46.3a & b.
118
Chapter III: Phoebodontid chondrichthyans of the Maider
Phoebodus: Newberry 1889; Ginter 1990; Ginter & Ivanov 1992, 1995; Ginter et al. 2002; Ginter et al. 2010; specimen PIMUZA/I 4656, PIMUZ A/I 4710, PIMUZ A/I 4712, PIMUZ A/I 4711, PIMUZ A/I 4713.
Poracanthodes: Denison 1979; Valiukevicius 1992. Promesacanthus: Hanke 2008; specimens UALVP 41672, 41859, 41860, 42652, 43027.Psarolepis: Yu 1998; Zhu & Schultze 1997; Zhu et al. 1999; Qu et al. 2013a.Ptomacanthus: Brazeau 2009, 2012; Denison 1979; Miles 1973a; specimens BM P.19999, 24919b.Pucapampella: Maisey 2001a; Maisey & Anderson 2001; Maisey & Lane 2010; Janvier & Maisey 2010.Raynerius: Giles et al. 2015b.Rhadinacanthus: Burrow et al. 2016.Squalus: Schaeffer 1981; Gans & Parsons 1964; Marinelli & Strenger 1959.Synechodus: Maisey 1985; NHM P.6135, 41675.Tamiobatis: Schaeffer 1981; Williams 1998; specimen FMNH PF5414.Tetanopsyrus: Gagnier & Wilson 1995; Gagnier et al. 1999; Hanke et al. 2001; specimens UALVP 32571,
38682, 39062, 39078, 42512, 43026, 43246, 44030, 43089.Thrinacodus: Turner 1982; Ginter 2000; Ginter & Sun 2007; Ginter & Turner 2010; Ginter et al. 2010;
Grogan & Lund 2008. Tribodus: Maisey & de Carvalho 1997; Lane 2010; Lane & Maisey 2009, 2012.Triodus: Solér-Gijon, R. & Hampe 1998; Hampe 2003; Heidtke et al. 2004.Tristychius: Dick1978; Coates & Gess 2007; Coates & Tietjen in press: specimens NMS 1972.27.455A,
1974.51.5A; HM V8299. Uraniacanthus: Bernacsek & Dineley 1977; Hanke & Davis 2008; Newman et al. 2012; Burrow et al.
2016; specimens UALVP 19259, 32448, 32469, 38679, 41669, 41857, 41858, 41862, 42095, 42095, 44046, 45366 to 45396.
Vernicomacanthus waynensis: Miles 1973a.Youngolepis: Chang & Yu 1981; Chang 1982, 1991, 2004.
4) Character listSkeletal tissues1 Tessellate calcifi ed cartilage: absent (0); present (1). Brazeau (2009); Coates & Sequeira (2001a,
b); Davis et al. (2012); Dean & Summers (2006); Dean et al. (2009); Grogan et al. (2012); Maisey (1984, 2001, 2013); Lund & Grogan (1997, 2004a, b); Seidel et al. (2016).
2 Perichondral bone: present (0); absent (1). Janvier (1996); Donoghue & Aldridge (2001); Brazeau (2009); Davis et al. (2012); Lund (1985); Coates et al. (1999).
3 Extensive endochondral ossifi cation: absent (0); present (1). Forey (1980); Gardiner (1984); Brazeau (2009); Davis et al. (2012).
4 Extensive calcifi ed cartilage: absent (0); present (1). This character refers to taxa where perichon-dral bone is absent but where cranial or postcranial skeletal parts consist of mineralized and therefore, more robust cartilage (Coates et al. 2018).
5 Dentine kind: mesodentine or semidentine (0); orthodentine (1). Donoghue et al. (2000); Brazeau (2009); Davis et al. (2012); Burrow et al. (2016). Orthodentine was coded as `non-applicable` in the data matrix of Grogan and Lund (2008). However, according to Ivanov (2000), the teeth of Thrinaco-dus contain orthodentine in the cusps and osteodentine in the base.
6 Pore canal network: absent (0); present (1). Lu et al. (2016).7 Acrodin tooth caps (enameloid cap restricted to crown apex): absent (0); present (1). Friedman
& Brazeau (2010); Zhu et al. (2013, 2009); Lu et al. (2016).
Squamation & related structures8 Trunk scales monocuspid (0); multicuspid (1). Revised after Davis et al. (2012); Burrow et al.
(2016). Scale growth differs among different groups of gnathostomes: scales of teleostomes (osteich-thyans and acanthodians) have a sustained growth whereas in non-teleostomes (chondrichthyans), the scales stop growing when reaching a determinate size (Nelson 1969; Reif 1985). However, in several Palaeozoic chondrichthyans, scales grow throughout their life (Nelson 1970; Zangerl 1981) and there-fore, limited scale growth is assumed to be a derived condition. In Phoebodus, we fi nd multicuspid scales, but their growth pattern is unkown thus far.
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Chapter III: Phoebodontid chondrichthyans of the Maider
9 Scale growth concentric: absent (0); present (1). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Burrow et al. (2016).
10 Peg-and-socket articulation: absent (0); present (1). Gardiner (1984); Coates (1999); Brazeau (2009); Davis et al. (2012).
11 Anterodorsal process on scale: absent (0); present (1). Zhu et al. (2009, 2013); Gardiner (1984); Coates (1999); Brazeau (2009); Davis et al. (2012).
12 Body scales with bulging base: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Burrow et al. (2016).
13 Body scales with fl attened base: absent (0); present (1). Brazeau (2009, 2012); Davis et al. (2012); Burrow et al. (2016).
14 Body scales with basal canal or open basal vascular cavity: absent (0); present (1). Placoid scales of both modern as well as early chondrichthyans (e.g. Akmonistion, Antarctilamna) are characterized by the presence of a basal canal (Reif 1978; Coates & Sequeira 2001a; Young 1982). Basal canals were identifi ed in disarticulated chondrichthyan scales such as Elegestolepis (Karatajūte-Talimaa 1992), Polymerolepis and Seretolepis (Hanke & Wilson 2010) as well as in a few acanthodian taxa such as Kathemacanthus, Tetanopsyrus (Hanke et al. 2001, fi g.2c), Lupopsyrus (Hanke and Davis 2012), and Ptomacanthus (Brazeau 2012, tentative identifi cation in fi g. 7D). Basal canals could not yet be identifi ed in the scales of Phoebodus.
15 Neck canal: absent (0) present (1). The presence of neck canals is a common feature in placoid scales, but neck canals were either found in scales of placoderms (Burrow & Turner 1998, 1999) and osteichthyans (Qu et al. 2013a, b).
16 Sensory line canal passes between or beneath scales (0); passes over scales and/or is partially
enclosed or surrounded by scales (1); perforates and passes through scales (2). Davis (2002); Friedman & Brazeau (2010); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014); Burrow et al. (2016). In Thrinacodus, the lateral line system of the mandibular region is enclosed by tesserate mineralized tissue.
17 Lepidotrichia or lepidotrichia-like scale alignment: present (0); absent (1). Davis et al. (2012).18 Epichordal lepidotrichia: absent (0); present (1). Zhu et al. (2009, 2013).19 Fringing fulcra: absent (0); present (1). Zhu et al. (2009, 2013); Coates (1999).20 Scute-like ridge scales (fulcra): absent (0); present (1). Giles et al. (2015c).
Cranial dermal skeleton21 Sclerotic ring: absent (0); present (1). Giles et al. (2015c); Qiao et al. (2016); Zhu et al. (2016);
Burrow et al. (2016). Sclerotic rings are present in early chondrichthyans such as Cladoselache (Lund 1986; Williams 2001; CMNH 8207 exhibits especially well preserved plates: pers. obs. MIC), Cobe-lodus (Zangerl & Case, 1976), Falcatus (Lund, 1985), Damocles (Lund, 1986), Ctenacanthus (Wil-liams, 2001), Gladbachus (Coates et al., 2018) and Iniopteryx (Zangerl & Case, 1973). No sclerotic ring is preserved in the available material of Phoebodus and Thrinacodus.
22 Number of sclerotic plates: four or less (0); more than four (1). Zhu et al. (2013, c170); Qiao et al. (2016, c.241); Zhu et al. (2016, c.239); Burrow et al. (2016).
23 Dermal ornamentation: smooth (0); parallel, vermiform ridges (1); concentric ridges (2); tuber-
culate (3). Giles et al. (2015c).24 Dermal skull roof includes large dermal plates (0); consists of undifferentiated plates, tesserae
or scales (1); naked or largely scale free (2). Forey (1980); Gardiner (1984); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).
25 Cranial tessera morphology: large interlocking plates (0); microsquamose, no larger than body
squamation (1). Brazeau (2009) through to Giles et al. (2015c).26 Anterior or mesial edge of nasal notched for anterior nostril: absent (0); present (1). Contra Zhu
et al. (2013), the anterior rim of the nasal in Cheirolepis is notched.27 Supraorbital: absent (0); present (1). Zhu et al. (2009, 2013).28 Large median bone contributes to posterior margin of skull roof: absent (0); present (1). Zhu et
al. (2016).29 Medial process of paranuchal wraps around posterolateral corners of nuchal plate: absent (0);
present (1); paranuchals precluded from nuchal by centrals (2); no median bone in posterior of
skull roof (3). Giles et al. (2015c).30 Pineal opening perforates dermal skull roof: present (0); absent (1). Davis et al. (2012); Giles et
120
Chapter III: Phoebodontid chondrichthyans of the Maider
al. (2015c).31 Consolidated cheek plates: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al.
(2012); Zhu et al. (2013); Burrow et al. (2016).32 Enlarged postorbital tessera separate from orbital series: absent (0); present (1). Brazeau (2009);
Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).33 Dermal intracranial joint: absent (0); present (1). Zhu et al. (2009, 2013)34 Foramina (similar to infradentary foramina) on cheek bones: absent (0); present (1). Zhu et al.
(2009, 2013).35 Preopercular bone: absent (0); present (1). Zhu et al. (2013).36 Maxilla expanded posteriorly: absent - splint shaped (0); present - cleaver shaped (1). Zhu et al.
(2009, 2013); Lu et al. (2016).37 Sensory line network preserved as open grooves (sulci) in dermal bones (0); sensory lines pass
through canals enclosed within dermal bones (1). (Davis 2002); Davis et al. (2012); Zhu et al. (2013).
38 Sensory canal or pit-line associated with maxilla: absent (0); present (1). Friedman (2007) 39 Jugal portion of infraorbital canal joins supramaxillary canal: present (0); absent (1). Brazeau
(2009), but see redefi nition in Davis et al. (2012); Zhu et al. (2013).40 Anterior pit line of skull roof: absent (0); present (1). Giles et al. (2015c).41 Spiracular opening in dermal skull roof bounded by bones carrying otic canal: absent (0); pres-
ent (1). Giles et al. (2015); Lu et al. (2016).42 Endolymphatic ducts open in dermal skull roof: present (0); absent (1). Janvier (1996); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013); Giles et al. (2015c). 43 Dermohyal (submarginal) ossifi cation: absent (0); present (1). 44 Dermohyal (submarginal) shape: broad plate that tapers towards its proximal end (0); narrow
plate (1). Brazeau’s (2009)45 Branchiostegal series: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).46 Opercular and subopercular bones: absent (0); present (1).
47 Branchiostegal plate series along ventral margin of lower jaw: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
48 Branchiostegal ossifi cations plate-like (0); narrow and ribbon-like (1); fi lamentous (2). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Lu et al. (2016).
49 Branchiostegal ossifi cations ornamented (0); unornamented (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
50 Branchiostegals imbricated: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
51 Opercular cover of branchial chamber complete or partial (0); separate gill covers and gill slits
(1). Lund & Grogan (1997); Hanke & Wilson (2004); Davis et al. (2012); Zhu et al. (2013). Condition ´1` is likely a synapomorphy of recent elasmobranchs although opercular covers are not present in most Paleozoic chondrichtyans (Coates et al. 2017, see data matrix discussion in Coates et al. 2018). Opercular cover in holocephalans secondarily evolved (cf. Coates et al. 2017).
52 Gular plates: absent (0); present (1). Gardiner (1984); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
53 Size of lateral gular plates: extending most of length of the lower jaw (0); restricted to the anteri-
or third of the jaw (no longer than the width of three or four branchiostegals) (1). Coates (1999); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
Hyoid and gill arches54 Gill skeleton mostly beneath otico-occipital region (0); mostly posterior to occipital region (1).
Zangerl (1981); Lund & Grogan (1997); Stahl (1999). Except for holocephalans, the gill skeleton is mostly located posteriorly to the neurocranium in chondrichthyans. In acanthodians, gill skeletons are located either beneath or posterior to the occipital region of the braincase.
55 Perforate hyomandibula: absent (0); present (1). Zhu et al. (2009, 2013); Lu et al. (2016).56 Interhyal: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013). 57 Ceratohyal smooth with posterior, lateral fossa: absent (0); present (1). Coates et al. (2018).
Characteristic feature in Recent and early elasmobranchs such as Egertonodus (Maisey 1983), Ortha-
121
Chapter III: Phoebodontid chondrichthyans of the Maider
canthus (Hotton 1952), Tristychius (Coates et al. 2018, supplementary Fig. 10e, f) and also Phoebo-dus (Fig. 1a-c).
58 Ceratohyal anteriorly blade-shaped: absent (0), present (1). The ceratohyal is a simple slightly curved, uniformely thick, rod-shaped cartilage in Recent and fossil chondrichthyans. Fossil examples are e.g. Akmonistion (Coates & Sequeira, 2001a), Denaea (Williams, 1985), Cobelodus (Zangerl & Case, 1976), Triodus (Heidtke et al., 2004) and Gladbachus (Coates et al., 2018). However, in Tristy-chius (pers. obs. MC) and Phoebodus, the ceratohyal exhibits a derived shape with the anteriormost portion laterally expanding. This is apparently not the condition in the phoebodont Thrinacodus, in which the ceratohyal shows a non-derived shape (Grogan & Lund, 2008, fi g. 10C). But because of the fl attened preservation of the Thrinacodus specimens, the character was coded as non-applicable.
59 Hypohyals: absent (0); present (1). Friedman & Brazeau (2010); Pradel et al. (2014). Present in osteichthyans and some Paleozoic chondrichthyans including Cobelodus, Akmonistion (Coates & Se-queira 2001a), Triodus (Heidtke et al. 2004; Hampe 2002, fi g. 18), Orthacanthus (Heidtke 1999, fi g. 7c) and possibly Falcatus (Lund 1985, fi g. 8b). Hypohyals were reconstructed for Thrinacodus gracia (Grogan & Lund 2008, fi g. 10C) while they are absent in Phoebodus (Fig. 1c), which corresponds to the condition in other chondrichthyans such as Gladbachus (Coates et al. 2018) and Tristychius (Coates & Tietjen 2018). In Acanthodes and stem group gnathostomes, hypohyals seem to be absent.
60 Basihyal absent, hyoid arch articulates directly with basibranchial (0); basihyal present (1).
Pradel et al. (2014); see also discussion in Carr et al. (2009); Brazeau et al. (2017). In osteichthyans, basihyals are rarely present and therefore, the hyoid arch articulates directly with basibranchials like in Acanthodes (Nelson 1968; Miles 1973b; Gardiner 1984). Basihyals are known from a variety of placoderms (Long 1997; Carr et al. 2009; Brazeau et al. 2017), and early and modern chondrichthyans (Zangerl &Case 1973, 1976; Maisey 1983; Didier 1995; see discussion in data matrix of Coates et al. 2018). In phoebodont chondrichthyans the basihyal is preserved in Phoebodus while it seems to be absent in Thrinacodus (Grogan & Lund 2008).
61 Separate supra- and infra-pharyngobranchials absent (0); present (1). Gardiner (1984); Pradel et al. (2014). Absent in many early gnathostome taxa such as Halimacanthodes, Acanthodes, Glad-bachus, Debeerius, Tristychius, hybodontids, and Triodus. Present in osteichthyans, but also in the chondrichthyan Ozarcus (Pradel et al. 2014).
62 Pharyngobranchials directed anteriorly (0); posteriorly (1). Pradel et al. (2014). Pharyngobran-chials are anteriorly directed in osteichthyans whereas in most chondrichthyans they are directed pos-teriorly. Among Paleozoic chondrichthyans posteriorly directed pharyngobranchials are known from e.g., Orthacanthus, Triodus, Debeerius, Tristychius and Falcatus (Coates et al. 2018, Lund 1985, fi g. 6). As exceptions, Gladbachus (Coates et al. 2018) and Ozarcus (Pradel et al. 2014) exhibit anteriorly directed pharyngobranchial elements. Pharyngobranchials are not known from Phoebodus yet.
63 Posteriormost branchial arch bears epibranchial unit: absent (0); present (1). Coates et al. (2018). Absent in osteichthyans; present in chondrichthyans, Gladbachus and Acanthodes (Davis et al. 2012; Pradel et al. 2014).
64 Epibranchials bear posterior fl ange: absent (0); present (1). Coates et al. (2018). Present in Acan-thodes (Coates et al. 2018, supplementary Fig. 9di), Gladbachus (Coates et al. 2018, supplementary Fig. 9dii), Halimacanthus (Burrow et al. 2012) and Ozarcus (Pradel et al. 2014).
65 Hypobranchials directed anteriorly (0); hypobranchials of second and more posterior gill arches
directed posteriorly (1). Coates et al. (2018). Hypobranchials are common in early osteichthyans and chondrichthyans but also in Acanthodes . Posteriorly directed: crown-chondrichthyans, xenacan-thids (Hampe 2002; Heidtke et al. 2004) and hybodontids. Anteriorly directed: Ozarcus and Falcatus (Coates et al. 2018).
Dentition & tooth-bearing bones and cartilages66 Oral dermal tubercles borne on jaw cartilages: absent (0); present (1). Hanke & Wilson (2004);
Brazeau (229); Davis et al. (2012); Zhu et al. (2013). 67 Pharyngeal teeth or denticles: absent (0); present (1). Commen feature in most early gnathostomes
except for placoderms. In early chondrichthyans: often small whorls on a fused base (Zangerl & Case 1976; Coates & Sequeira 2001a). Other shapes/arrangements of pharyngeal teeth are present in the hybodontid Hamiltonichthys (Maisey 1989) and Tribodus (Lane & Maisey 2012, Figs 4.1, 5). Disar-ticulated specimens are preserved in Phoebodus.
68 Tooth families/whorls: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
122
Chapter III: Phoebodontid chondrichthyans of the Maider
(2009); Davis et al. (2012); Zhu et al. (2013).69 Bases of tooth families/whorls: single, continuous plate (0); some or all whorls consist of sepa-
rate tooth units (1). Adjusted by Coates et al. (2018) from Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Giles et al. (2015).
70 Lingual torus: absent (0); present (1). After Ginter et al. 2010; Coates et al. (2018). Present in most Palaeozoic chondrichthyans, exception: holocephalans with tooth plates.
71 Basolabial shelf: absent (0); present (1). After Ginter et al. (2010): The basolabial shelf at the tooth base articulates with the tooth crown of the overlying tooth of the same tooth family. Common feature in Palaeozoic chondrichthyans.
72 Tooth families/whorls restricted to symphysial region (0); distributed along jaw margin (1). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). Character score ´1` is likely a synapomorphic condition of chondrichthyans (Tucker and Fraser 2014, Coates et al. 2018).
73 Number of tooth families/whorls per jaw ramus: 15 or fewer (0); 20 or more (1). Coates et al. (2018). Character not applicable in Phoebodus because dentition is mostly disarticulated and/or not complete.
74 Toothplates absent (0); present (1). Follows defi nition of Coates et al. (2018): tooth plates are de-fi ned by fused adjacent tooth families.
75 Toothplate complement restricted to two pairs in the upper jaw and a single pair in the lower
jaw: absent (0); present (1). After Patterson (1965); Coates et al. (2018).76 Mandibular teeth fused to dermal plates on biting surfaces of jaw cartilages: absent (0); present
(1). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). 77 Dermal plates on biting surface of jaw cartilages: absent (0); present (1). Brazeau (2009); Davis
et al. (2012); Zhu et al. (2013); Giles et al. (2015c).78 Gnathal plates mesial to and/or above (or below) jaw cartilage: absent (0); present (1). Zhu et al.
(2016).79 Maxilla and premaxilla sensu stricto (upper gnathal plates lateral to jaw cartilage without pala-
tal lamina): absent (0); present (1). Zhu et al. (2016).80 Dentary bone encloses mandibular sensory canal: absent (0); present (1). Gardiner (1984) and
references therein; Zhu et al. (2009, 2013).81 Infradentary foramen and groove, series: absent (0); present (1). Zhu et al. (2010).82 Tooth-bearing median rostral: absent (0); present (1). Zhu et al. (2009, 2013).83 Median dermal bone of palate (parasphenoid): absent (0); present (1). Gardiner (1984); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013).84 Denticulated fi eld of parasphenoid: without spiracular groove (0); with spiracular groove (1).
Friedman (2007); Zhu et al. (2009, 2013).85 Denticle fi eld of parasphenoid with multifi d anterior margin: absent (0); present (1). Friedman
(2007); Zhu et al. (2009, 2013); Lu et al. (2016).
Mandibular arch86 Large otic process of the palatoquadrate: absent (0); present (1). Coates & Sequeira (2001a);
Davis (2002); Brazeau (2009); Zhu et al. (2009, 2013). In Paleozoic chondrichthyans, the palatoquad-rate is usually cleaver-shaped with a dorsoventrally large otic process. Examples are xenacanthids (Schaeffer 1981), symmoriiforms (Coates and Sequeira, 2001a, Zangerl 1981) and cladoselachians (Zangerl 1981). The otic process of Phoebodus shows a derived short shape (Fig. 1a-c). This contrasts the condition in Thrinacodus, in which the palatoquadrate appears to be higher (Grogan & Lund 2008, fi g. 10B). In hybodontids, the otic process is short but the quadrate expands laterally to form a deep adductor fossa (Maisey 1982).
87 Oblique ridge or groove along medial face of palatoquadrate: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Lu et al. (2016). Present in Acanthodes and chondrich-thyans such as Gladbachus and Orthacanthus.
88 Fenestration of palatoquadrate at basipterygoid articulation: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Lu et al. (2016).
89 Perforate or fenestrate anterodorsal (metapterygoid) portion of palatoquadrate: absent (0);
present (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).90 Articulation surface of the palatoquadrate with the postorbital process directed anteriorly (0);
laterally (1); dorsally (2). Coates et al. (2017). Character varies among early gnathostomes and even
123
Chapter III: Phoebodontid chondrichthyans of the Maider
within the chondrichthyans: e.g. anteriorly in Acanthodes, Orthacanthus, Tamiobatis and Phoebodus; laterally (or anterolaterally) in Cobelodus and Akmonistion; dorsally in Tristychius.
91 Palatoquadrate fused to the neurocranium: absent (0); present (1). Coates et al. (2017).92 Pronounced dorsal process on Meckelian bone or cartilage: absent (0); present (1). Davis (2002);
Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016). 93 Mandibular mesial process: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et
al. (2013); Burrow et al. (2016). Synonyms of the mandibular mesial process are mandibular knob, preglenoid articular process, or mandibular condyle. It describes the auxiliary articular facet of the double jaw articulation in chondrichthyans (Hotton 1952; Maisey 1989a; Lane & Maisey 2012).
94 Jaw articulation located on rearmost extremity of mandible: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013).
95 Dental sulcus (trough) adjacent to oral rim on Meckel’s cartilage and palatoquadrate: absent
(0); present (1). Coates et al. (2017). Characteristic feature of chondrichthyans, but absent in Glad-bachus as well as in holocephalans having toothplates. This character is not present in Phoebodus.
96 Scalloped oral margin on Meckel’s cartilage and palatoquadrate: absent (0); present (1). Coates et al. (2017). Characteristic of some symmoriiform chondrichthyans such as Akmonistion, Ozarcus, and Cladoselache, but also present in Helodus (pers. obs. MIC).
97 Mandibular symphysis fused: absent (0); present (1). Coates et al. (2017).
Neurocranium98 Internasal vacuities: absent (0); present (1). Lu et al. (2016). 99 Precerebral fontanelle: absent (0); present (1). Schaeffer (1981); Lund & Grogan (1997); Coates &
Sequeira (1998, 2001a, b); Maisey (2001a); Brazeau (2009); Pradel et al. (2011) Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).
100 Space for forebrain and (at least) proximal portion of olfactory tracts narrow and elongate,
extending between orbits: absent (0); present (1). Coates et al. (2017).101 Prominent, pre-orbital, rostral expansion of the neurocranium: present (0); absent (1). Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013). Present in chimaeroids (Giles et al. 2015c).102 Rostral bar: absent (0); present (1). Adapted from Maisey (1985); Coates et al. (2017). 103 Internasal groove absent (0); present (1). Coates et al. (2017); present in Iniopera and Dwykasela-
chus (Pradel 2010).104 Orbitonasal lamina dorsoventrally deep: absent (0); present (1). Patterson (1965); Davis et al.
(2012); Zhu et al. (2013); Coates et al. (2017). Present in chimaeroids and some Palaeozoic holoceph-alans including Debeerius, Chondrenchelys, and Helodus (Coates et al. 2018).
105 Palatobasal (or orbital) articulation posterior to the optic foramen (0); anterior to the optic
foramen, grooved, and overlapped by process or fl ange of palatoquadrate (1); anterior to optic
foramen, smooth, and overlaps or fl anks articular surface on palatoquadrate (2). Adapted by Coates et al. (2018) from Pradel et al. (2011, character 26), Coates et al. (2017, character 71) and Maisey (2005, p.61)
106 Trochlear nerve foramen anterior to optic nerve foramen: absent (0); present (1). Coates & Se-queira (2001). Characteristic in hybodontids, absent in Tristychius (Coates & Tietjen 2018).
107 Supraorbital shelf broad with convex lateral margin: absent (0); present (1). Coates & Sequeira (1998); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
108 Orbit directed mostly laterally and free of fl anking endocranial cartilage or bone: absent (0);
present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Coates et al. 2018). 109 Interorbital space broad (0); narrow (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013);
Coates et al. (2017).110 Optic pedicel: absent (0); present (1). Dupret et al. (2014); Zhu et al. (2009, 2013); Coates et al.
(2017).111 Ophthalmic foramen in anterodorsal extremity of orbit communicates with cranial interior:
absent (0); present (1). Coates et al. (2017).112 Extended prehypophysial portion of sphenoid: absent (0); present (1). Brazeau (2009); Davis et
al. (2012); Zhu et al. (2013).113 Canal for efferent pseudobranchial artery within basicranial cartilage: absent (0); present (1).
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).114 Entrance of internal carotids: through separate openings fl anking the hypophyseal opening or
124
Chapter III: Phoebodontid chondrichthyans of the Maider
recess (0); through a common opening at the central midline of the basicranium (1). Schaeffer (1981); Coates & Sequeira (1998); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
115 Internal carotids: entering single or paired openings in the basicranium from a posterolateral
angle (0); entering basicranial opening(s) head-on from an extreme, lateral angle (1); absent (2). Coates et al. (2017).
116 Ascending basisphenoid pillar pierced by common internal carotid: absent (0); present (1). Miles (1973b); Brazeau (2009); Friedman & Brazeau (2010); Davis et al. (2012); Zhu et al. (2013).
117 Spiracular groove on basicranial surface: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013).
118 Spiracular groove on lateral or transverse wall of jugular canal: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013).
119 Spiracular groove open (0); enclosed by spiracular bar or canal (1). Lu et al. (2016), Coates et al. (2018).
120 Orbit larger than otic capsule: absent (0); present (1). Lund & Grogan (1997); Coates et al. (2017).121 Postorbital process and arcade: absent (0); present (1). Pradel et al. (2011); see also Maisey (2007)
and Coates et al. (2017). Character absent in crown group elasmobranchs (Coates et al. 2018).122 Postorbital process and arcade short and deep - width not more than maximum braincase width
(excluding arcade) (0); process and arcade wide - width exceeds maximum width of braincase,
and anteroposteriorly narrow (1); process and arcade massive (2); arcade forms postorbital
pillar (3). Coates et al. (2017). 123 Postorbital process downturned, with anhedral angle relative to basicranium: absent (0); pres-
ent (1). Present in hybodontids, Acronemus (Maisey 2011) and Tristychius (Dick 1978; Coates & Tietjen 2018).
124 Jugular canal diameter small (0); large (1); canal absent (2). Pradel et al. (2011); see Coates et al. (2018) for defi nition of small and large canals.
125 Canal, likely for trigeminal nerve (V) mandibular ramus, passes through the postorbital process
from proximal dorsal entry to distal and ventral exit: absent (0); present (1). Present in early chondrichthyans such as Cladodoides (Maisey, 2005), Dwykaselachus (Coates et al., 2017), Ortha-canthus, Tamiobatis and Pucapampella. In the latter two taxa, the canal was initially interpreted as the branch of the palatine nerve (Schaeffer 1981; Maisey 2001) but later reinterpreted by Coates et al. (2018). Also in Acanthodes the canal was reinterpreted (Coates et al. 2018) which was formerly described as the canal for the middle cerebral vein and a branch of the lateral line nerve (Davis et al. 2012). No such canal is evident in early actinopterygians (Gardiner 1984), Janusiscus, or placoderms.
126 Postorbital process expanded anteroposteriorly: absent (0); present (1). Generally a characteristic feature of hybodontids, but absent in Tristychius (Coates et al. 2018).
127 Postorbital process articulates with palatoquadrate: absent (0); present (1). Schaeffer (1981); Coates & Sequeira (1998); Maisey (2001a); Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013). Archaeostyly (Maisey 2008; here corresponding to character state ´1`) is a characteristic feature of early chondrichthyans and some acanthodians such as Acanthodes and Promesacanthus (Coates et al. 2018). In the neoselachian Synechodus, the archaeostylic condition secondarily evolved (Maisey 1985).
128 Trigemino-facial recess: absent (0); present (1). Goodrich (1930); Gardiner (1984 and references therein); Pradel (2010); Pradel et al. (2011); Davis et al. (2012).
129 Jugular canal long, extends throughout most of otic capsule wall posterior to the postorbital
process (0); short and/or groove present on exterior of otic wall (1); absent, path of jugular re-
moved from otic wall (2). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Giles et al. (2015c); Coates et al. (2017).
130 C-bout notch separates postorbital process from supraotic shelf: absent (0); present (1). Charac-teristic feature of Tristychius, present in Acronemus (Maisey 2011).
131 Postorbital fossa: absent (0); present (1). Zhu et al. (2013).132 Hyoid ramus of facial nerve (N. VII) exits through posterior jugular opening: absent (0); pres-
ent (1). Friedman (2007); Brazeau (2009); Friedman & Brazeau (2010); Davis et al. (2012); Zhu et al. (2013).
133 Periotic process: absent (0); present (1). Maisey (2007); Coates et al. (2017).134 Articulation facet for hyomandibula: single-headed (0), double-headed (1). Zhu et al. (2009,
2013).
125
Chapter III: Phoebodontid chondrichthyans of the Maider
135 Relative position of jugular groove and hyomandibular articulation: hyomandibula dorsal or
same level (i.e. on bridge) (0); jugular vein passing dorsal or lateral to hyomandibula (1). Brazeau & de Winter (2015).
136 Transverse otic process: absent (0); present (1). Lu et al. (2016); Giles et al. (2016) 137 Craniospinal process: absent (0); present (1). Giles et al. (2015); Lu et al. (2016). 138 Lateral otic process: absent (0); present (1). Schaeffer (1981); Coates & Sequeira (1998); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013). The lateral otic process projects far posteriorly from the otic region and it connects the hyomandibula to the braincase (Schaeffer 1981; Coates & Sequeira 1998). Such a process is well-known from Orthacanthus and Tamiobatis. The character is currently coded as ´0` in Akmonistion, because the “short, posterolateral angle” of the otic differs reasonably in shape from the lateral otic process in Orthacanthus and Tamiobatis (Coates et al., 2018). In Clado-doides (Maisey 2005) as well as in Phoebodus, lateral projections from the otic capsular wall are completely absent.
139 Hyomandibula articulates with neurocranium beneath otic shelf: absent (0); present (1).
140 Sub-otic occipital fossa: absent (0); present (1). Coates et al. (2017, 2018). See Schaeffer (1981; p. 15, fi g. 6, occipital view): concavity underneath the lateral otic process. The feature is present in Orthacanthus and Tamiobatis (Schaeffer 1981), but not in Cladodoides which has a similar braincase (Maisey 2005). For Phoebodus, the character was coded as inapplicable but it is most probably absent.
141 Postotic process: absent (0); present (1). Pradel et al. (2011); Coates et al. (2017).142 Otic capsule extends posterolaterally relative to occipital arch: absent (0); present (1). Maisey
(1985).143 Otic capsules: widely separated (0); approaching dorsal midline (1). Coates et al. (2017).144 Otic capsules project anteriorly between postorbital processes: absent (0); present (1). Present
in neoselachians (Maisey 1983) and probably in some early elasmobranchs, e.g., Acronemus (Maisey 2011).
145 Endocranial roof anterior to otic capsules dome-like, smoothly convex dorsally and anteriorly:
absent (0); present (1). Coates et al. (2017).146 Roof of skeletal cavity for cerebellum and mesencephalon signifi cantly higher than dorsal-most
level of semicircular canals: absent (0); present (1). Coates et al. (2017).147 Roof of the endocranial space for telencephalon and olfactory tracts offset ventrally relative to
level of mesencephalon: absent (0); present (1). Coates et al. (2017).148 Labyrinth cavity separated from the main neurocranial cavity by a cartilaginous or ossifi ed
capsular wall (0); skeletal medial capsular wall absent (1). Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013).
149 Double octaval nerve foramena in chondrifi ed mesial wall of otic capsule: absent (0); present
(1). Present in Tribodus and Egertonodus (Lane 2010); absent in chondrichthyans exhibiting a medial capsular wall (e.g Tristychius; Coates & Tietjen 2018).
150 External (horizontal) semicircular canal joins the vestibular region dorsal to posterior ampulla
(0); joins level with posterior ampulla (1). Davis et al. (2012); Zhu et al. (2013).151 Angle of external semicircular canal: in lateral view, straight line projected through canal in-
tersects anterior ampulla, external ampullae, and base of foramen magnum: absent (0); present
(1). Coates et al. (2017).152 Left and right external semicircular canals approach or meet the posterodorsal midine of the
hindbrain roof: absent (0); present (1). Coates et al. (2017).153 Preampullary portion of posterior semicircular canal absent (0); present (1). Coates et al. (2017).
Known from crown chondrichthyans (Daniel 1922; Maisey 2001b; Maisey & Lane 2010).154 Crus commune connecting anterior and posterior semicircular canals present (0); absent (1).
Coates et al. (2017). A crus commune is present in most early chondrichthyan groups (e.g. Coates et al. 2017, Maisey 2005, 2007, Schaeffer 1981). However, some hybodontids show a derived condition (posterior and anterior semicircular canals are separated from each other) such as in modern elasmo-branchs (Daniel 1922, Maisey 2001b, Maisey and Lane 2010, Pradel et al. 2011).
155 Sinus superior: absent or indistinguishable from union of anterior and posterior canals with
saccular chamber (0); present, elongate and nearly vertical (1). Davis et al. (2012); Zhu et al. (2013).
156 Lateral cranial canal: absent (0); present (1). Zhu et al. (2009, 2013); Lu et al. (2016). Character is present in early actinopterygians (Gardiner 1984; Coates 1998) and a putative stem osteichthyan
126
Chapter III: Phoebodontid chondrichthyans of the Maider
(Basden et al. 2000). 157 Endolymphatic ducts: posteriodorsally angled tubes (0); tubes oriented vertically through endo-
lymphatic fossa/posterior dorsal fontanelle (1). Schaeffer (1981); Coates & Sequeira (1998, 2001); Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
158 Posterior dorsal fontanelle connected to persistent otico-occipital fi ssure (0); posterior tectum
separates fontanelle from fi ssure (1). Schaeffer (1981); Coates & Sequeira (1998); Pradel et al. (2011).
159 Subcircular endolymphatic foramen: absent (0); present (1). Pradel et al. (2015), Coates et al. 2017. Character was renamed from subcircular endolymphatic fossa to subcircular endolymphatic foramen by Coates et al. (2017). It was suggested as a holocephalan synapomorphy (Maisey & Lane 2010).
160 External opening for endolymphatic ducts anterior to crus commune: absent (0); present (1). Coates et al. (2017).
161 Supraotic shelf broad: absent (0); present (1). Present in Tristychius and Acronemus (Maisey 2011).162 Dorsal otic ridge: absent (0); present (1). Coates & Sequeira (1998, 2001); Maisey (2001); Davis
(2002); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).163 Dorsal otic ridge forms a crest posteriorly: absent (0); present (1). Coates & Sequeira (1998,
2001); Pradel et al. (2011).164 Endolymphatic fossa: absent (0); present (1). Pradel et al. (2011). 165 Endolymphatic fossa elongate (slot-shaped), dividing dorsal otic ridge along midline: absent (0);
present (1). Coates et al. (2017). 166 Perilymphatic fenestra within the endolymphatic fossa: absent (0); present (1). Pradel et al.
(2011); Coates et al. (2017).167 Ventral cranial fi ssure: absent (0); present (1). Janvier (1996); Coates & Sequeira (2001); Maisey
(2001); Davis (2002); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013).168 Endoskeletal intracranial joint: absent (0); present (1). Janvier (1996); Davis et al. (2012); Zhu et
al. (2013).169 Metotic (otic-occipital) fi ssure: absent (0); present (1). Schaeffer (1981); Janvier (1996); Coates
& Sequeira (1998); Maisey (2001); Davis (2002); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013).
170 Vestibular fontanelle: absent (0); present (1). Brazeau (2009); Friedman & Brazeau (2010). Davis et al. (2012); Zhu et al. (2013).
171 Hypotic lamina: absent (0); present (1). Schaeffer (1981); Maisey (1984, 2001); Brazeau (2009); Pradel et al. (2011, 2013); Davis et al. (2012); Zhu et al. (2013); Coates et al. (2017).
172 Glossopharyngeal nerve path: directed laterally, across fl oor of the saccular chamber and exits
via foramen in side wall of the otic capsule (0); directed posteriorly, and exits through metotic
fi ssure or foramen in posteroventral wall of otic capsule (1); exits laterally through a canal con-
tained ventrally (fl oored) by the hypotic lamina (2); exits through a foramen anterior to the pos-
terior ampulla (3). Coates et al. (2017), adapted from Schaeffer (1981); Coates & Sequeira (1998, 2001); Brazeau (2009): Davis et al. (2012); Zhu et al. (2013); Pradel et al. (2011, 2013).
173 Glossopharyngeal and vagus nerves share common exit from neurocranium: absent (0); present
(1). Uniquely present in hybodontids such as Egertonodus and Tribodus.174 Basicranial morphology: platybasic (0); tropibasic (1). Brazeau (2009); Pradel et al. (2011); Davis
et al. (2012); Zhu et al. (2013). Defi nition of tropibasic versus platybasic: see Maisey (2007) and Pradel et al (2011).
175 Channel for dorsal aorta and/or lateral dorsal aortae passes through basicranium (0): exter-
nal to basicranium (1). Schaeffer (1981); Coates & Sequeira (1998); Brazeau (2009); Pradel et al. (2011); Brazeau & Friedman (2014); Coates et al. (2017).
176 Dorsal aorta divides into lateral dorsal aortae posterior to occipital level (0); anterior to level of
the occiput (1). Pradel et al. (2011); Giles et al. (2015); Coates et al. (2017).177 Ventral portion of occipital arch wedged between rear of otic capsules: absent (0); present (1).
Schaeffer (1981); Coates & Sequeira (1998); Maisey (2001a); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Coates et al. (2017).
178 Dorsal portion of occipital arch wedged between otic capsules: absent (0); present (1). Schaeffer (1981); Coates & Sequeira (1998); Maisey (2001a); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Coates et al. (2017).
127
Chapter III: Phoebodontid chondrichthyans of the Maider
179 Occipital crest anteroposteriorly elongate, and extends from the roof of the posterior tectum:
absent (0); present (1). The elongate condition (posterior tectum to the level of foramen magnum) is present in Callorhinchus and in the Palaeozoic chondrichthyans Kawichthys (Pradel et al. 2011, fi g. 5) and Iniopera (Pradel 2010, fi g. 5) (see Finarelli & Coates 2014). In contrast, Dwykaselachus, Akmonistion and FMNH PF 13242 (Maisey 2007, fi g. 7), show an anteroposteriorly short occipital crest (not exceeding the level of the anterior margin of the occipital fi ssure). The character is coded as ´absent` in Phoebodus, Orthacanthus, Triodus and hybodontids because their occipital crests extend from the occipital arch wedged between the otic capsules (Schaeffer 1981; Maisey 1982).
Axial and appendicular skeleton180 Calcifi ed vertebral centra: absent (0); present (1). Maisey (1985): biconcave calcifi ed vertebral
centra are absent in Palaeozoic chondrichthyans and therefore this character is suggested as a synapo-morphy of crown elasmobranchs (Coates et al. 2017).
181 Chordacentra: absent (0); present (1). Stahl (1999); Coates and Sequeira (2001); Coates et al. (2017). Known in Chondrenchelys (Finarelli & Coates 2014), Damocles (Lund 1986; CM 48760), Falcatus (Lund 1985) and in the caudalis of Akmonistion (Coates & Sequeira 2001).
182 Chordacentra polyspondylous and consist of narrow closely packed rings: absent (0); present
(1). Derived from Patterson (1965); Coates et al. (2017).183 Synarcual: absent (0); present (1). Stahl (1999); Brazeau (2009); Davis et al. (2012); Zhu et al.
(2013); Coates et al. (2017).184 Macromeric dermal pectoral girdle (0); micromeric or lacking dermal skeleton entirely (1).
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).185 Macromeric dermal pectoral girdle composition: ventral and dorsal components (0); ventral
components only (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).186 Macromeric pectoral dermal skeleton forms complete ring around the trunk: present (0); ab-
sent (1). Goujet & Young (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).187 Median dorsal plate: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).188 Scapular process (dorsal) of shoulder endoskeleton: absent (0); present (1). Coates & Sequeira
(2001a); Zhu & Schultze (2001); Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).
189 Ventral margin of separate scapular ossifi cation: horizontal (0); deeply angled (1). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
190 Cross sectional shape of scapular process: fl attened or strongly ovate (0); subcircular (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).
191 Flange on trailing edge of scapulocoracoid: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).
192 Scapular process with posterodorsal process: absent (0); present (1). Coates & Sequeira (2001a); Davis et al. (2012); Zhu et al. (2013).
193 Mineralisation of internal surface of scapular process: mineralised all around (0); un-min-
eralised on internal face forming a hemicylindrical cross-section. Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).
194 Coracoid process: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).195 Procoracoid mineralisation: absent (0); present (1). Davis (2002); Hanke & Wilson (2004): Brazeau
(2009).196 Fin base articulation on scapulocoracoid: stenobasal, deeper than wide (0); eurybasal, wider
than deep (1). Lu et al. (2016).197 Pectoral fi n articulation monobasal (0); dibasal (1); three or more basals (2).
198 Metapterygium pectinate subtriangular plate or bar supporting numerous (six or more) radials
along distal edge: absent (0); present (1). Present in symmoriiforms and Diplodoselache.199 Metapterygial whip: absent (0); present (1). Coates et al. (2017).200 Biserial pectoral fi n endoskeleton: absent (0); present (1). Lu et al. (2016).201 Propterygium perforated: absent (0); present (1). Rosen et al. (1981); Patterson (1982); Davis et
al. (2012); Zhu et al. (2013).202 Pelvic girdle with fused puboischiadic bar: absent (0); present (1). Maisey (1984); Coates & Se-
queira (2001a); Coates et al. (2017).203 Mixipterygial/mixopterygial claspers: absent (0), present (1). Coates & Sequeira (2001a,b);
128
Chapter III: Phoebodontid chondrichthyans of the Maider
Brazeau & Friedman (2014). 204 Pre-pelvic clasper or tenaculum: absent (0); present (1). After Patterson (1965); Coates et al.
(2017).205 Number of dorsal fi ns, if present: one (0); two (1); one, extending from pectoral to anal fi n level
(2). Coates & Sequeira (2001a); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).206 Brush complex of bilaterally distributed calcifi ed tubes fl anking or embedded in calcifi ed carti-
lage core: absent (0); present (1). Coates et al. (2017, 2018); description of Brush complex in Lund (1985) and Coates et al. (1998). The rod-like structure in Falcatus and the brush complex in Akmonis-tion are homologous (Maisey 2009; Coates et al. 2018)
207 Posterior or pelvic-level dorsal fi n with calcifi ed base plate: absent (0); present (1). Coates & Sequeira (2001a, b). Present in Tristychius, hybodontids, and “Ctenacanthus”. Character was coded with state ´1` for Phoebodus because the specimen shows remains of cartilage ventrally to the dorsal fi n spine.
208 Posterior dorsal fi n with delta-shaped cartilage: absent (0); present (1). Coates & Sequeira (2001a, b). Present in many symmoriid taxa; absent in Cladoselache.
209 Posterior or pelvic-level dorsal fi n shape, base approximately as broad as tall and not broader
than other median fi ns (0); base much longer than fi n height, substantially longer than other
median fi ns (1). Brazeau & deWinter (2015); Lu et al. (2017). 210 Anal fi n: absent (0); present (1). Coates & Sequeira (2001); Brazeau (2009); Davis et al. (2012);
Zhu et al. (2013).211 Anal fi n base narrow, posteriormost proximal segments radials broad: absent (0); present (1).
Heidtke (1999). Present in xenacanthids, exception: Diplodoselache. 212 Caudal radials restricted to axial lobe (0); extend beyond level of body wall and deep into hypo-
chordal lobe (1). Davis et al. (2012); Zhu et al. (2013). 213 Caudal neural and/or supraneural spines or radials short (0); long, expanded, and supporting
high aspect-ratio (lunate) tail with notochord extending to posterodorsal extremity (1); noto-
chord terminates pre-caudal extremity, neural and heamal radial lengths near symmetrical and
support epichordal and hypochordal lobes respectively (2). Coates & Sequeira (2001a, b).
Spines: fi ns, cranial and elsewhere214 Dorsal fi n spine or spines: absent (0); present (1). Zhu et al. (2001); Zhu & Yu (2002); Friedman
(2007); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Lu et al. (2016). 215 Dorsal fi n spine at anterior (pectoral level) location only: absent (0); present (1). Coates & Sequei-
ra (2001a); Ginter et al. (2010). This character has been coded inapplicable in taxa having a continu-ous dorsal fi n extending throughout trunk length (Coates et al. 2017, 2018).
216 Dorsal fi n spine cross section: horseshoe shaped (0); fl at sided, with rectangular profi le (1); sub-
circular (2). Hampe (2002); Brazeau & de Winter (2015).217 Anterior dorsal fi n spine leading edge concave in lateral view: absent (0); present (1). This char-
acter is present in chondrichthyan genera in which fi n spines form derived shapes such as brush com-plexes or hook-like extensions. Examples are mostly symmoriids such as Akmonistion, Falcatus and Damocles but also Physonemus, which is a taxon based on fi n spines (Lund 1985, 1986). However, such fi n spines are known from males only and they are probably absent in females (Lund 1985; Maisey 2009). Therefore, the usefulness of this character is still challenged (Coates et al. 2018).
218 Anal fi n spine: absent (0); present (1). Maisey (1986); Davis (2002); Brazeau (2009).219 Pectoral fi n spines: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu
et al. (2013).220 Pectoral fi n spine with denticles along posterior surface: absent (0); present (1). Burrow et al.
(2016).221 Prepectoral fi n spines: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013). Present in Doliodus (Maisey et al. 2017).222 Admedian pectoral spines absent (0); present (1). Burrow et al. (2016); see also description of
Doliodus pectoral girdle (Maisey et al. 2017).223 Median fi n spine insertion: shallow, not greatly deeper than dermal bones/ scales (0); deep (1).
Davis (2002); Hanke & Wilson (2004); Brazeau (2009). Davis et al. (2012); Zhu et al. (2013).224 Intermediate (pre-pelvic) fi n spines: absent (0); present (1). Davis (2002); Hanke & Wilson (2004);
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). Pre-pelvic spines are generally absent in early
129
Chapter III: Phoebodontid chondrichthyans of the Maider
and recent chondrichthyans. Doliodus is an exception (Maisey et al. 2017).225 Fin spines with ridges: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al. (2012);
Zhu et al. (2013).226 Fin spines with nodes: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009). Davis et al. (2012); Zhu et al. (2013).227 Fin spines (dorsal) with rows of large denticles: absent (0); on posterior surface (1); on lateral
surface (2). Maisey (1989b); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).228 Cephalic spines: absent (0); present (1). Maisey (1989); Coates et al. (2017)
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CHAPTER IV
Functional morphology of mandibular arches in symmoriids
as exemplifi ed by Ferromirum oukherbouchi gen. et sp. nov.
(Late Devonian)
Linda Frey, Michael Coates, Martin Rücklin and Christian Klug
In preparation, formatted for Science Advances
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Functional morphology of mandibular arches in symmoriids as ex-
emplifi ed by Ferromirum oukherbouchi gen. et sp. nov. (Late Devoni-
an, Morocco)
L. Frey1*, M. I. Coates2, M. Rücklin3 and C. Klug1
1Paläontologisches Institut und Museum, University of Zurich, Karl-Schmid-Strasse 4, CH-8006 Zürich ([email protected]; [email protected]). 2Department of Organismal Biology and Anatomy, University of Chicago, 1027 E. 57th St., USA-60637 Chicago.3 Naturalis Biodiversity Center, Postbus 9517, 2300 RA, Leiden, The Netherlands.
The functional morphology of mandibular and branchial arches in early chondrichthyans is poorly known because of the lack of articulated and undistorted fossil material. A recently discovered exceptionally well-preserved specimen of the symmoriiform Ferromirum oukherbouchi gen. et sp. nov. of Famennian age from the southern Maïder (Morocco) yields new information about the anatomy and function of the cranial and visceral skeleton. A three-dimensional model based on CT-scans of the holotype shows the undeformed mandibular and branchial arches such as the hyoids and ceratohyals allowing the reconstruc-tion of mandible movement during feeding. The way the Meckel’s cartilages rotate around their sagittal axes was previously unknown from chondrichthyans and probably became extinct with the end of the symmoriid clade. At the same time, the new species corroborates that cranial morphology of Palaeozoic symmoriiforms is quite conservative and allowed to falsify the aphetohyoidean hypothesis for these early chondrichthyans, because in the new taxon, the hyoid is tightly attached to the lower jaw.
Key words: chondrichthyans, gnathostomes, jaws, Famennian, Maïder, Palaeozoic
1. Introduction
The evolution of the structured visceral skeleton including jaws was a fundamental step in ver-tebrate evolution as it opened up the access to a much greater variety of food sources. The visceral skeleton of chondrichthyans, osteichthyans, and extinct stem gnathostomes including placoderms and acanthodians consists of paired, serially ar-ranged lower and upper jaws, jaw supporting el-ements (hyoids and ceratohyals) and gill arches [1-6]. Knowledge of morphological details and the function of jaws in Devonian chondrichthyans is still poor, mostly due to incompleteness or de-formation of specimens. With a few exceptions [7-9], the visceral skeleton and the jaws are of-ten disarticulated and/ or distorted by compaction or tectonics. Therefore, reconstructions of feed-ing mechanisms of Palaeozoic chondrichthyans are largely based on tooth morphology and ar-rangement in combination with comparisons to analogous or homologous conditions in Recent chondrichthyans [10-15]. As in modern chon-drichthyans, the dentitions of Devonian chon-drichthyans display a great morphologic disparity corresponding to a similarly wide range of feed-ing strategies. Chondrichthyans with cladodont or phoebodont teeth were grasping prey, which they
swallowed in one piece while forms with prot-acrodont or orodont teeth were likely duropha-gous [14]. Filter feeding chondrichthyans such as Diademodus were rarely reported from the Palae-ozoic so far; they usually have minute teeth com-pared to jaw size [13]. Other feeding modes such as suction feeding were inferred for hybodontid chondrichthyans from the Carboniferous based on their mandibular and branchial skeletons [16].
The function of jaws and branchial arches of the Symmoriiformes is hardly known although it is a very common and geographically widely distributed group of early chondrichthyans with cladodont teeth. It is known from the Devonian and Carboniferous and was recently assigned to the holocephalans branch within the chondrich-thyans [17]. Although complete skeletons [18-23] and braincases [17, 24-26] of several species were described in the last decades, branchial arches and jaws in three-dimensional preservation remained unknown. In a recently discovered symmoriiform chondrichthyan from the Devonian of Morocco, superbly preserved and articulated branchial and mandibular arches are preserved. These remains reveal the fi rst insights into the feeding mecha-nism of these early holocephalans.
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2. Results
2.1 Systematic palaeontology and anatomical
description
Class Chondrichthyes Huxley, 1880Order Symmoriiformes Zangerl, 1981Family ?Falcatidae Zangerl, 1990Genus Ferromirum gen. nov.
Type species. Ferromirum oukherbouchi gen. et sp. nov.
Etymology. Derived from ferrum (lat. - iron) and mirus (lat. - miraculous). Ferrum is includ-ed because of the preservation of the holotype of the type species in a reddish ferruginous nodule, which is characteristic for fossils from the Thyla-cocephalan Layer of the Maïder. Mirus refers to the fact that we erroneously interpreted the gill re-mains of the holotype as appendages of a crusta-cean, and it was like a miracle when a chondrich-thyan emerged.
Genus defi nition. Small symmoriid with slen-der body; head with rounded triangular outline, rostrum protruding anterior of the mouth; large orbits; tessellated cartilage; jaws amphystylic; cladodont teeth; cleaver-shaped palatoquadrate; fi ve gill arches; otico-occipital fi ssure; narrow suborbital shelf; palatoquadrate ventrally sig-moid; coronoid process on Meckel`s cartilage; tri-angular pelvic girdle; anterior fi n spine broad and dorsally recurved.
Included species. Only the type species.
Systematic remarks. Although the cladistics analysis did not resolve the family-position of the new taxon, we tentatively assign it to the Fal-catidae for the following reason: There are cur-rently seven other genera included in this clade: Dwykaselachus has a short rostrum; Ozarcus has a different geometry of the palatoquadrate and a rostrum like in Ferromirum seems missing; Cladoselache has short fi n spines; Cobelodus lacks the anterior dorsal fi n and fi n spine as well as a shorter rostrum; the jaws are quite similar in Ferromirum and Akmonistion, but the latter has a large spine-brush complex; Damocles and Fal-catus share the small body size, the slender body, similar jaws, a neurocranium protruding anterior-ly in front of the palatoquadrate, and the strongly developed dorsal fi n spine above the pectoral gir-dle with Ferromirum but differ in the shape of the fi n spine. Taking these differences and similarities
into account, we suggest that Ferromirum might be the only Devonian and thus oldest member of the Falcatidae.
Ferromirum oukherbouchi gen. et sp. nov.
Holotype. PIMUZ A/I XXXX
Material. Only the holotype.
Locality and horizon. Famennian, Planitornoc-eras euryomphalum to Afrolobites mrakibensis Zone; Ibaouane Formation, Lahfi ra Member, Thy-lacocephalan Layer (formerly described as Phyl-locarid Layer; [27]), Madene el Mrakib, Maïder Basin, southeastern Anti-Atlas, Morocco.
Etymology. The species name oukherbouchi hon-ours the fi nder of the specimen Said Oukherbouch (Tafraoute).
Species defi nition. As for genus.
Description
The complete body of Ferromirum oukherbouchi gen. et sp. nov. is approximately 33 cm long. It was prepared from its ventral side. Thus, ventral parts of the pectoral and pelvic girdles, branchi-al and mandibular arches and of the left orbit are exposed (Fig. 1A, B). In the anterior part of the head region, a rostrum like in Falcatus and Dam-ocles [20-21] is present and some soft tissues such as both elongate wings of the liver, parts of the digestive tract and parts of the body outline are preserved. The computed tomograms and the re-constructed 3D-model show much more anatom-ical details of the braincase, pectoral and pelvic girdles, as well as a fi n spine (Fig. 2A-D). The visceral skeleton shows a basic arrangement with serially arranged paired mandibular and hyoid arches and fi ve gill arches as known from Ozarcus mapesae [8].
Mandibular arches
The mandibular arches underwent very little dis-tortion and compression (Fig. 3A-I) and there-fore, they represent the best-preserved jaws cur-rently known from symmoriid chondrichthyans. The palatoquadrate of Ferromirum gen. nov. is cleaver-shaped with a high otic process, which is a common feature in symmoriids and other Pa-laeozoic chondrichthyans [10, 28]. Anteriorly, the otic process articulates with the postorbital pro-
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Fig. 1. Ferromirum oukherbouchi gen. et sp. nov., PIMUZ XXXX, early/ middle Famennian, Madene el Mrakib. (A) Photo and (B) line drawing of the specimen. (C) Head region including parts of the braincase, sclerotic ring, mandib-ular arches and branchial skeleton and shoulder girdles from ventral view. (D) Soft tissue remains including liver and spiral valves. (E) Pelvic and caudal region. Abbreviations - chy: ceratohyal; cop: copula; cbr: ceratobranchials; fs: fi n spine; liv: liver; mc: Meckel`s cartilage; p.pl: pelvic plate; pq: palatoquadrate; ros: rostrum; scl.r: sclerotic ring; scor; scapulacoracoid; stc?: stomach content; spv: spiral valves. Scales: A-B = 100 mm; C-E = 30 mm.
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Chapter IV: Functional Morphology of Symmoriid Jaws
Fig. 2. Ferromirum oukherbouchi gen. et sp. nov. PIMUZ XX, virtually reconstructed specimen based on CT-data showing the neurocranium, mandibular arches the pectoral girdle and the dorsal fi n spine. Ventral (A) and dorsal view with (B) and without (C) braincase. (D) lateral view. Colour coding: grey, braincase; turquoise, palatoquadrate; yellow, Meckel’s cartilage; dark green, hypohyal; light blue, hyoid; orange, ceratohyal; blue, epihyals; red, cerato-branchials; green, copula; brown, fi n spine; purple, shoulder girdle; light turquoise, ? neural arches.
cess of the neurocranium. A distinctive otic crest at the dorsoposterior margin of the palatoquadrate is present. A second smaller crest is situated on the most anterior part of the dorsal margin of the otic process (anterodorsal crest) that serves as a support for nerve VII (Fig. 3C, D). Laterally, the quadrate region of the palatoquadrate is strongly
concave forming a large attachment area for ad-ductor muscles. The ventral margin of the entire palatoquadrate is sigmoid like in Stethacanthidae [19, 23] and Falcatidae [20-21]. Dorsally, the pal-atine region is mediolaterally expanded similar to Ozarcus [8]. Anteromedially, a serrated margin articulates with the ethmoid region of the neuro-
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Chapter IV: Functional Morphology of Symmoriid Jaws
Fig. 3. Mandibular arches of Ferromirum oukherbouchi gen. et sp. nov., PIMUZ XX. Right and left palatoquadrates in dorsal (A) and ventral (B) view. Right palatoquadrate, lateral (C) and medial (D) view. (E) Right and left Meck-el’s cartilage in ventral aspect. Right Meckel’s cartilages in lateral (F), medial (G), dorsal (H) and ventral (I) views. Abbreviations: adc, anterodorsal crest; gl, glenoid; ma, mandibular articulation; mp, mandibular process; oa: orbital articulation; oaf, otic articular fossa; opr, otic process; ppr, palatine process; sym, symphysis.
cranium. Like the palatoquadrate, the Meckel`s cartilages have a prominent lateral concavity in the posterior portion (Fig. 3E-I). The ventroposte-rior jaw margin forms a distinctive crest. Dorsal-ly, the mediolateral expanded margin bears eight small circular concavities for tooth families. At two thirds of its length, the dorsal margin of the Meckel`s cartilage shows a coronoid process pos-teriorly followed by a concavity similar to Falca-tus [20]. For the articulation with the palatoquad-rate, two processes including the mesial process (also known as mandibular knob; [29]) and the
glenoid mandibular process are present posterior-ly of the Meckel`s cartilage.
Branchial arches
Like in Ozarcus, the preserved hyoid arches in-clude paired epihyals, ceratohyals and hypohyals [8], while pharyngohyals, interhyals and basihy-als are not preserved (maybe poorly calcifi ed) in Ferromirum gen. nov. Both the ceratohyals and epihyals are closely aligned to the mandibular arches throughout their complete length. This
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contrasts the condition in Ozarcus and Cobelodus where some space seems to be left between the hyoid and mandibular arches (fi n 3 a in [8]; [30]). With the new anatomical data of Ferromirum gen. nov. provided here, the supposed space between the hyoid and mandibular arches in Ozarcus and Cobelodus is likely taphonomically biased. Both the upper and lower hyoid arches are slightly curved and posteriorly, the hyoid is inserted in the articular notch of the ceratohyal. Anteriorly, the dorsoventrally broad end of the hyoid articulates with the lateral otic region of the braincase.
From the gill arches, fi ve pairs of epibranchi-als and of seven ceratobranchials are present. All are rod-shaped, and have a smooth surface (unlike Tristychius [31]). The basibranchial copula [32] in Ferromirum gen. nov. is long and of rectangu-lar shape but its articulation with basibranchials is unknown. Smaller elements such as hypobran-chials, infrapharyngobranchials and suprapharyn-gobranchials reported from Ozarcus [8] are not recognizable.
Neurocranium and sclerotic ring
The neurocranium of Ferromirum gen. nov.is somewhat deformed. It shows a somewhat com-pressed ethmoidal and orbital region, while the otic and occipital regions are three-dimensionally preserved (Fig. 4A-D). The overall shape of the braincase shows the affi nity of this specimen to other symmoriids. At the anterolateral edges of the narrow subotic shelf of the ethmoid, a serrated margin for the articulation with the palatine ramus of the palatoquadrate is present. The orbital region shows the common condition as in holocephalans: its size is very large and about the same length as the otic and occipital regions together [17]. A large opening for the optic nerve II is perforating the interorbital wall. The postorbital process is laterally broken but it is rather thin anteroposte-riorly compared to the rest of the braincase. From the dorsal view, only little anatomical detail of the otic region is recognizable. Characteristical-ly for early chondrichthyans, the occipital unit is wedged between the otic capsule and traces of an otic-occipital fi ssure are preserved. The hyoman-dibula articulates with the otic unit posterior to the postorbital process. However, a periotic pro-cess is not recognizable where the hyomandibula is supposed to articulate (see e.g., Cobelodus in [25]; Dwykaselachus in [17]). Ventrally and pos-teriorly to the postorbital process, the otic region shows a waist typical for symmoriids [e.g., 17]. The otic region and the glossopharyngeal canals are fl oored by a hypotic lamina, which exhibits
two openings for the lateral dorsal aortae far pos-teriorly. In the occipital region, the occipital plate is perforated by the foramen magnum.
Remains of a deformed sclerotic ring are ex-posed (Fig. 1A-C), but its fi ne morphological de-tails are not preserved. Sclerotic rings are formed by numerous sclerotics in Cladoselache [33], Fal-catus [20] and Damocles [21].
Pectoral girdle
Right and left parts of the pectoral girdle are pres-ent, where the left part is better preserved. The scapulacoracoid of Ferromirum gen. nov. has a shape characteristic for symmoriiform chondrich-thyans [e.g. 10, 24]. The fl at, sheet-like scapula is dorsoventrally long and bears an anteriorly directing process (anterior process) at the dorsal apex (Fig. 5A-E). The region bearing the posteri-ordorsal process is broken (compare fi g. 10A-C in [24]). Anteriorly and posteriorly, the scapula has a concave outline. Towards the ventral end, the scapulacoracoid is mediolaterally broadening. In ventral view, the base of the scapulacoracoid ap-pears triangularly and its posterior portion shows a concavity for the articulation with the proximal radials of the pectoral fi n. The coracoid region is convex anteriorly and concave posteriorly. A pro-coracoid has not been detected but was probably present as in, e.g., Akmonistion and other symmo-riids.
Pelvic girdle
The pelvic girdle is poorly preserved in Fer-romirum gen. nov.; only a small, simple triangular plate is visible posterior of a pyrite concretion, which possibly is located in the middle of the body (Fig. 1B, E). In other symmoriiform chondrich-thyans such as Akmonistion, Cobelodus, Denaea and Symmorium, the pelvic plate is subtrianglar to oval in shape [10, 24]. In Falcatus, it is triangular but the anterolateral edge is concave [20]. Trian-gular plates are present in Cladoselache (fi g. 18 in [33]) and xenacanthids [fi g. 12a-b in [34]; fi g. 14 in [35]).
Fin spine
A dorsal fi n spine on the pectoral level is pre-served between the pectoral girdle and the pos-terior end of the neurocranium in Ferromirum gen. nov.. It resembles the fi ns spines of cladose-lachians [10, 36] in having an anteroposteriorly broad shape and a strongly recurved dorsal apex. Its position is comparable to genera such as Fal-catus or Stethacanthus. By contrast, the fi n spine
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Chapter IV: Functional Morphology of Symmoriid Jaws
Fig. 4. Ferromirum oukherbouchi gen. et sp. nov., PIMUZ XX. Neurocranium in dorsal (A), ventral (B), lateral (C) and posterior (D) views. (E) Articulation between braincase and visceral arches. (F-G) Arrangement of mandibular and branchial arches. Colour coding: grey, braincase; turquoise, palatoquadrate; yellow, Meckel’s cartilage; dark green, hypohyal; light blue, hyoid; orange, ceratohyal. Abbreviations: fm, foramen magnum; hl, hypotic lamina; hya, hyomandibular articulation; glc, glossopharyngeal canal; oa, orbital articulation; ocpl, occipital plate; oof, otico-oc-cipital fi ssure; popr, postorbital process; sup.s, supraorbital shelf; II, optic nerve.
Fig. 5. Virtually reconstructed pectoral elements and the fi n spine (possibly slightly distorted) of Ferromirum oukher-bouchi gen. et sp. nov., PIMUZ XX. Left part of the pectoral girdle in anterior (A), lateral (B, D), posterior (C) and ventral (E) views. (F) dorsal fi n spine of the pectoral fi n-level. Abbreviations: apr, anterior process; cor, coracoid; ppr, posterior process; sc, scapula.
144
Chapter IV: Functional Morphology of Symmoriid Jaws
of Ferromirum gen. nov. is longer and more slen-der than in Cladoselache (Fig. 5F). The dorsal fi n on the pelvic level is not visible in the CT-scan and possibly absent.
2.2 Phylogenetic relationships
Phylogenetic analyses resulted in 730 parsimoni-ous trees of 545 steps. The strict consensus tree based on the data matrix including 228 characters, 66 ingroup taxa and one outgroup taxon plac-es Ferromirum gen. nov. within the Symmorii-formes (Fig. 6, S1). Ferromirum gen. nov. shares the narrow interorbital space, the absence of anal fi ns, the presence of a fi n spine at pectoral level and a longer orbit compared to the otic unit (in Ferromirum gen. nov. only subtly longer) with other stem Holocephali. The presence of a scle-rotic ring is shared with other Symmoriiformes (Cladoselache, Falcatus and Damocles).
Although our phylogenetic analyses does not ful-ly resolve the relation within the symmoriiform clade, the small size, body proportions, shape of the head (including shape of the palatoquadrate, pointed rostrum) and the presence of one fi n spine in the pectoral region of Ferromirum gen. nov. are reminiscent of the Falcatidae (Fig. 7). In the light of this systematic proximity, the absence of a well-developed dorsal fi n and a posterior fi n spine can be considered primary. An assignment to this family would extend the stratigraphic range of the Falcatidae from the Early Carboniferous into the Late Devonian, which is not surprising tak-ing the bizarre morphological specialisations of the Carboniferous falcatids into account. More discoveries of postcranial material of Dwykasela-chus, Ozarcus and Ferromirum, in particular, will help reconstructing the phylogenetic relationships among symmoriids and testing the hypothesis of Ferromirum being a falcatid.
Doliodus
Acronemus
Egertonodus
Hamiltonichthys
Onychoselache
Tribodus
Squalus
Synechodus
Tristychius
Homalodontus
Cladodoides
Phoebodus
Thrinacodus
Diplodoselache
Orthacanthus
Triodus
Tamiobatis
Dwykaselachus
Ozarcus
Cladoselache
Cobelodus
Akmonistion
Damocles
Falcatus
Debeerius
Chimaeroidei
Chondrenchelys
Helodus
Iniopera
Kawichthys
Ferromirum gen. nov
Fig. 6. Crown part of the strict consensus tree showing phylogenetic affi liation of Ferromirum gen. nov. to sym-moriform chondrichthyans. Colour coding: orange, stem Chondrichthyes without Acanthodii; blue, Elasmobranchii (crown Chondrichthyes); purple, Holocephali (crown Chondrichthyes). White circles: bootstrap support of knot > 50% and/ or Bremer decay values > 1; black circles: bootstrap support > 75% and/or Bremer decay values > 3. For the complete cladogram, see Fig. S1.
145
Chapter IV: Functional Morphology of Symmoriid Jaws
Fig. 7. Possible reconstruction of Ferromirum oukherbouchi gen. et sp. nov. and the thylacocephalans found in the
Famennian of the Maïder region of Morocco.
2.3 Functional morphology of the mandibular
arches
Symmoriiformes show morphological conserva-tism in the jaw to braincase articulation among all its genera. This was tested by rescaling the braincase of Dwykaselachus oosthuizeni recon-structed by Coates [17] to the dimensions of the well-preserved jaws of Ferromirum oukherbouchi gen. et sp. nov. and by virtually combining them. All these elements fi t perfectly together, corrob-orating their close relationships and functional similarities. The quadrate process articulates an-teriorly with the postorbital process and serrated edges of the palatine ramus joints with the orbital articulation of the braincase (Fig. 8A-B).
Using a 3D-print of the computationally vi-sualized 3D-model, the movement of the jaws was reconstructed. The shape of the jaw articula-tion makes the Meckel`s cartilage rotate laterally while it is dropping. Therefore, a larger surface of the dentition is presented to the water column and prey (Fig. XX and video in preparation). When
the animal closed its mouth, the Meckel’s carti-lage rotates back into its initial position, i.e. both lower jaws rotated inward, possibly thereby im-proving the grip on prey items.
3. Discussion
The neurocranial-mandibular articulation is quite conservative in symmoriiform chondrichthyans as demonstrated by the perfect fi t between the palatoquadrate of the Late Devonian Ferromirum oukherbouchi gen. et sp. nov. and the braincase of the much younger Early Permian Dwykaselachus. The jaws fi t similarly well to the braincase of oth-er symmoriiforms such as Akmonistion or Cobe-lodus. Therefore, this type of articulation and its function changed hardly through the evolution of this group.
The three-dimensionally preserved mandibu-lar arches enabled us to reconstruct the jaw func-tion of these early chondrichthyans. Although the
146
Chapter IV: Functional Morphology of Symmoriid Jaws
Fig. 8. Neurocranium of Dwykaselachus oosthuizeni Oelofsen, 1986 virtually articulated with the mandibular arches (pink and blue) of Ferromirum oukherbouchi gen. et sp. nov. A, mouth closed. B, mouth opened; note the inward rotation along the sagittal axes when the mouth closes and the outward rotation during opening, which created a larger surface exposing functional teeth.
feeding mechanisms in extant chondrichthyans are also poorly known, they display a high diversity in prey capture including ram feeding, biting, suc-tion feeding, and fi lter feeding [37]. By contrast, the jaws are amphystylic in Palaeozoic chondrich-thyans, thus implying a rather stiff articulation be-tween the braincase and the jaws. Therefore, they did not perform jaw propulsion while snatching the prey as observable in extant elasmobranchs with hyostylic jaws. The amphystylic jaw articu-lation combined with grasping teeth suggests ram feeding for symmoriiforms, phoebodontids, and xenacanthids [2, 12, 14, 15, 24, 38]. Additionally, the shape of the jaw articulation in Ferromirum gen. nov. revealed a lateral rotation of the Meck-el`s cartilage while the animal was opening and closing its mouth. Therefore, a larger surface of the dentition becomes exposed to the prey, there-by optimizing its predatory success. This partic-ular feeding ecomorphology is unknown from Recent chondrichthyans and might have vanished with the extinction of symmoriiforms. The mor-phology of the visceral skeleton of Ferromirum gen. nov. differs from Palaeozoic chondrichthyans that performed suction prey capture. Early suction feeders such as some hybodontids exhibit reduced teeth, labial cartilages enclosing the mouth and a massive ceratohyal that fl exibly articulates with the mandibular arches as it is involved in the suc-tion movement [16]. In the new symmoriiform portrayed here, labial cartilages are absent and the ceratohyals are slender and closely attached to the jaws (Fig. 4G), which were not suitable for suc-tion feeding.
The discovery of Ferromirum gen. nov. also challenges hypotheses on the arrangement and function of branchial arches in early gnatho-stomes. During the last fi fty years, there was a debate about if whether an aphetohyoidean con-dition in early symmoriiform chondrichthyans existed or not [7, 8, 10, 18, 25, 30]. The apheto-hyoidean hypothesis suggests that the hyoid was not closely attached to the upper jaw and there-fore, the hyoid lacked a suspensory function be-tween the mandibular arch and the braincase [39, 40]. This hypothesis seemed to be supported by a space between the hyoid and the upper jaws in the falcatid Ozarcus mapesae [8]. Accordingly, interpretations of cladoselachians and Cobelodus as a non-aphetohoidean [7, 25] were doubted. The well-preserved branchial and mandibular arches of Ferromirum gen. nov. show that indeed the hyoid was very closely aligned to the mandibular arch without a gap and therefore, the hyoid had a supporting function. This new result falsifi es the aphetohyoidean hypothesis for symmoriiform chondrichthyans.
To conclude, Ferromirum oukherbouchi gen. et sp. nov. is a new symmoriid which refl ects the morphological conservatism of the Symmorii-formes and its well-preserved visceral skeleton shows that the hyoid had a suspensory function, thereby falsifying the aphetohyoidean hypothesis. The reconstruction of the exceptionally preserved upper and lower jaws provide fi rst evidence for the jaw function in symmoriiform chondrich-thyans. As jaw function (subtle rotation of the lower jaws) is unknown from any other Palaeo-
147
Chapter IV: Functional Morphology of Symmoriid Jaws
zoic (and probably Recent) chondrichthyan so far, these fi ndings signifi cantly improve the knowl-edge about the ecomorphological diversity of their early relatives.
4. Material and methods
4.1 Specimen and anatomical reconstruction
based on computered tomograms
The here described specimen (PIMUZ A/I XXXX) of Ferromirum oukherbouchi gen. et sp. nov. is housed at the Palaeontological Institute and Museum of the University of Zurich, Swit-zerland. The specimen was prepared out of a fer-ruginous reddish nodule (rich in haematite) from the Famennian (Late Devonian) of Madene El Mrakib in the Maïder region of the southeastern Anti-Atlas (Morocco).
The specimen was CT-scanned using an indus-trial computer tomography scanner (Nikon XT H 225 ST) at the University of Zurich, Switzerland. Data acquisition and image reconstruction param-eters are: 224 kV, 474μA; fi lter: 4mm of copper; voxel sizes in mm: x = 0.091, y= 0.091, z = 0.091; 16-bit TIFF images were acquired; 8-bit TIFF im-ages were used for reconstruction.
Reconstruction of the 3D model was performed using Mimics v.17 (http://www.biomedical.ma-terialise.com/mimics; Materialise, Leuven, Bel-gium) and the reconstructed 3D-object was edited (smoothing, colours and lightning) in MeshLab v. 2016 (http://www.meshlab.net; [41]) and blend-er v2.79b (https://www.blender.org; Amsterdam, Netherlands). 3D prints of the palatoquadrates and Meckel`s cartilages were made to reconstruct jaw biomechanics of this early chondrichthyan.
For the phylogenetic analysis, the data ma-trix of Frey et al. [27] was used. This matrix is based on gnathostome data matrices of Coates et al. [9, 17] and Brazeau [42], which contains data on Acanthodii published by Davis et al. [43] and Burrow et al. [44] and data on the outgroup from Zhu et al. [45] and Qiao et al. [46]. 228 characters, 66 ingroup taxa and one outgroup taxon (Entelo-gnathus) were included in this data matrix. TNT 1.5 (Tree Analysis Using New Technology [41]) was used to perform phylogenetic analyses via heuristic parsimony analysis (traditional search in TNT) using 10000 multiple random addition sequences and swapping algorithm: tree bisection reconnection (TBR) with 10 trees saved per rep-lication. The data was resampled by using 1000
bootstrap replicants (standard bootstrap and tra-ditional search options in TNT 1.5) and Bremer support retaining trees suboptimal by 5 steps was performed for calculating the nodal supports.
Acknowledgments
General: We are deeply indebted to Saïd Oukhar-bouch (Tafraoute, Morocco) who discovered the holotype and who supported us during fi eld work.
The holotype was prepared by the team of the Tahiri Museum of Fossils and Minerals (Erfoud, Morocco). Anita Schweizer (Zurich) and Alexan-dra Wegemann (University of Zurich) kindly ac-quired CT-scans for us. Many thanks to Thodoris Argyriou (University of Zurich) who helped seg-menting the image stack.
Funding: The project (number S-74602-11-01) was fi nancially supported by the Swiss National Science Foundation.
Author contributions: L.F.: segmentation of computer tomographs, preparing fi gures, drafting manuscript. C.K., M.C., L.F., creating the project. C.K.: photography. M.C.: 3D-printing, interpreta-tion of 3D-models. All authors contributed to the text.
Competing interests: The authors declare no competing interests.
Data and materials availability: In preparation.
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Entelognathus
Youngolepis
Guiyu
Psarolepis
Cheirolepis
Mimipiscis
Raynerius
Moythomasia
Culmacanthus
Ischnacanthus
Nerepisacanthus
Poracanthodes
Tetanopsyrus
Uraniacanthus
Diplacanthus
Rhadinacanthus
Cassidiceps
Mesacanthus
Promesacanthus
Cheiracanthus
Acanthodes
Homalacanthus
Halimacanthodes
Gladbachus
Brachyacanthus
Brochoadmones
Climatius
Parexus
Ptomacanthus
V waynensis
Gyracanthides
Latviacanthus
Pucapampella
Kathemacanthus
Lupopsyrus
Obtusacanthus
Doliodus
Acronemus
Egertonodus
Hamiltonichthys
Onychoselache
Tribodus
Squalus
Synechodus
Tristychius
Homalodontus
Cladodoides
Phoebodus
Thrinacodus
Diplodoselache
Orthacanthus
Triodus
Tamiobatis
Dwykaselachus
Ozarcus
Cladoselache
Cobelodus
Akmonistion
Damocles
Falcatus
Debeerius
Chimaeroidei
Chondrenchelys
Helodus
Iniopera
Kawichthys
Ferromirum gen. nov
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4
258
5/85
5/71
5/66
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2
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SUPPLEMENTARY FIGURE
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Chapter IV: Functional Morphology of Symmoriid Jaws
Supplementary material
2. Taxa and sources
Acanthodes: Beznosov 2009; Brazeau & de Winter 2015; Coates 1994; Davis et al. 2012; Heidtke 1993, 2011a,b; Jarvik 1977, 1980; Miles 1968, 1973a, b; Nelson 1968; specimens AMNH 1037b, 10370, 10376, 19628; CMNH 30725b, 30726, 4591; FMNH PF2875; GM C145, 146, 180; HM V8251, 252; HU MB.F.4209, 4277, 4284, 4285, 7286, MB3b, 4a & b, 5a & b, 7a & b, 8a & b, 11a & b, 12a, 13a &b, 14a &b, 16a &b, 17a & b, 18a & b, 23 (resin copy), 24, MM L1693, 1698, 9432B, W1994; NHM P.11287, P.13139, 13140, 14558, 1728, 34912, 34914, 4057, 49941, 49944, 49959, 49967, 49979, 49980, 49990, 49995, 49996, 60928, 60939, 62138, 7335; NMS 2001.7.1, 3; UCL GM C1126; UMZC GN9, 11, 13, 14, 15a &b, 16, 39, 756.
Acronemus: Maisey 2011; Rieppel 1982.Akmonistion: Coates & Sequiera 1998, 2001a, b; Coates et al. 1998; Coates et al. 2017.Brachyacanthus: Denison 1979; Miles 1973a; Watson 1937; specimens NMS Kinnaird 88, NMS (Powrie)
1891.92.212, 213, 214, 220, 222, 224, 225, 226, 227.Brochoadmones: Bernacsek & Dineley 1977; Gagnier & Wilson 1996b; Hanke & Wilson 2006; specimens
UALVP 32672, 41487, 41493, 41494, 41495.Callorhinchus/Hydrolagus: Cole 1896; De Beer 1937; De Beer & Moy-Thomas 1935; Didier 1995; Didier
et al. 1994, 2012; Howard et al. 2013; Kesteven 1937; Patterson 1965, 1992; Pradel et al. 2013; Stahl 1999.
Cassidiceps: Gagnier & Wilson 1996a; specimen UALVP 32454.Cheiracanthus: Denison 1979; Miles 1973a; Watson 1937; specimens AMNH 317, 6929, 7082; GM C295,
296, 325, 490; HM V7614; IC 214, 215, 216, 217; UMZC GN14a &b, 19, 20, 21, 31, 50; 1131a & b, 1132a & b, 1133a & b, 1134a & b, 1135a & b, 1136a & b, 1137a & b, 1138, 1139, 1140.
Cheirolepis: Arratia & Cloutier 1996; Pearson & Westoll 1979; Giles et al. 2015a.Chondrenchelys: Finarelli & Coates 2012, 2014; Lund 1982; Moy-Thomas 1935; specimens NMS
1885.54.5/5A, 1891.53.33, 1998.35.1, 2002.68.1; BGS-GSE 13328; HM V.7173.Cladodoides: Gross 1937, 1938; Maisey 2005.Cladoselache: Bendix-Almgreen 1975; Harris 1938a, b; Maisey 1989a, 2007; Schaeffer 1981; Williams
2001; Woodward & White 1938; specimens CMNH 8110, 8111, 8207, NHM P9273, P9285.Climatius: Miles 1973a, b; Watson 1937: specimens AMNH 7762; GSM 49785; MM L12096a & b; NMS
Kinnaird 80; NMS 1881.5.62; NMS 1887 (Peach) 35.3a, 35.5b, 35.5e; NMS 1891 (Powrie) 92.195, 204, 206, 214; NMS 1967.12.4; NMS 1973.9.4; NMS 2001.7.2.
Cobelodus: Zangerl & Case 1976; Zidek 1992.Culmacanthus: Long 1983.Damocles: Lund 1986: specimens CM 35472, 48760.Debeerius: Grogan & Lund 2000: specimens CM 35479, 35480, 48831, 62811.Ferromirum oukherbouchi gen. et sp. nov.: holotype specimen PIMUZ XX.Diplacanthus: Gagnier 1996; Miles 1973a; Watson 1937; specimens FMNH PF11633; GM C12, 13, 148;
GM P482; MM L5503, 1609; NMS (Powrie) 1891.92.334; NMS 2001.7.4; UMZC GN17, 18, 22.Diplodoselache: Dick 1981.Doliodus: Miller et al. 2003; Maisey et al. 2009, 2013, 2017; Long et al. 2015.Dwykaselachus: Coates et al. 2017; Oelofsen 1986; specimen SAM K5840.Egertonodus: Maisey 1982, 1983; Lane, 2010.Entelognathus: Zhu et al. 2013.Falcatus: Lund 1985; Maisey 2007; specimens CM 35465, 37532.Gladbachus: Heidtke & Krätschmer 2001; Heidtke 2009; Burrow & Turner 2013; specimen UMZC
2000.32.Guiyu: Zhu et al. 2009.Gyracanthides: Miles 1973a; Warren et al. 2000; Turner et al. 2005.Halimacanthodes: Burrow et al. 2012.Hamiltonichthys: Maisey 1989b.Helodus: Patterson 1965; Stahl 1999; specimens NHM P.6706, 8207, 8209, 8212, 8213.Homalacanthus: Gagnier 1996; Watson 1937; specimens FMNH PF4875; MM LL12452.Homalodontus: Mutter et al. 2007, 2008.
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Iniopera: Zangerl & Case 1973; Pradel et al. 2009, Pradel 2010; Pradel et al. 2010.Ischnacanthus; Miles 1973a; Watson 1937; specimens GM C3, 6, 149, 324; GM P298; MM L9522, 9431,
9432; MM STR0585; NMS (Powrie) 92.254, 258; UALVP 32401, 32405, 32414, 39060, 39075, 40478, 41491, 41861, 42201, 42215, 42660, 43245, 44048, 44049, 44091, 45014.
Kathemacanthus: Gagnier & Wilson 1996a; Hanke & Wilson 2010; specimens UALVP 32402, 42269, 43113.
Kawichthys: Pradel et al. 2011.Latviacanthus: Schultze & Zidek 1982.Lupopsyrus: Hanke & Davis 2012; Bernacsek & Dineley 1977; specimens NMC 22700B, 22700C, 22715,
22718, 22719, 22700D, 22700E, 22700F, 22701C, 22701D, 22716, 22717, 22720, 22745; UALVP 19260, 32420, 32442, 32456, 32458, 32474, 32476, 32480, 32482, 39065, 39067, 39079, 39080, 39081, 39082, 39121, 41493, 41629, 41632, 41665, 41931, 41939, 41945, 42000, 42002, 42008, 42012, 42013, 42027, 42046, 42061, 42113, 42142, 42150, 42173, 42208, 42274, 42518, 42524, 42529, 42530, 42533, 42538, 42453, 42454, 42455, 42544, 42597, 42605, 43064, 43091, 43092, 43094, 43095, 43256, 43409, 43456, 45154, 45155.
Mesacanthus: Miles 1973a; Watson 1937; specimens FMNH PF1439; GM C18, 288a &b; NMS (Powrie) 1891.92.275; UMZC GN1143.
Mimipiscis: Gardiner & Bartram 1977; Gardiner 1984; Choo 2011; Giles & Friedman 2014.Moythomasia: Gardiner & Bartram 1977; Gardiner 1984; Coates et al. 2017; specimen MV P222915.Nerepisacanthus: Burrow 2011; Burrow & Rudkin 2014.Obtusacanthus: Hanke & Wilson 2004; specimen UALVP 41488.Onychoselache: Dick & Maisey 1980; Coates & Gess 2007.Orthacanthus: Heidtke 1982, 1999; Hotton 1952; Schaeffer 1981; Maisey 1983; Lane & Maisey 2009.Ozarcus and FMNH PF 13242: Maisey 2007; Pradel et al. 2014; Coates et al. 2017.Parexus: Watson 1937; Miles 1973a. specimens AMNH 1163, 7766; NMS Kinnaird 94; NMS (Peach)
1887.35.3a, 5e; NMS 1891 (Powrie) 92.183, 184, 186, 188, 194, 197, 207; NMS 1956.14.4.15; NMS 1977.46.3a & b.
Phoebodus: Newberry 1889; Ginter 1990; Ginter & Ivanov 1992, 1995; Ginter et al. 2002; Ginter et al. 2010; specimen PIMUZA/I 4656, PIMUZ A/I 4710, PIMUZ A/I 4712, PIMUZ A/I 4711, PIMUZ A/I 4713.
Poracanthodes: Denison 1979; Valiukevicius 1992. Promesacanthus: Hanke 2008; specimens UALVP 41672, 41859, 41860, 42652, 43027.Psarolepis: Yu 1998; Zhu & Schultze 1997; Zhu et al. 1999; Qu et al. (2013).Ptomacanthus: Brazeau 2009, 2012; Denison 1979; Miles 1973a; specimens BM P.19999, 24919b.Pucapampella: Maisey 2001a; Maisey & Anderson 2001; Maisey & Lane 2010; Janvier & Maisey 2010.Raynerius: Giles et al. 2015b.Rhadinacanthus: Burrow et al. 2016.Squalus: Schaeffer 1981; Gans & Parsons 1964; Marinelli & Strenger 1959.Synechodus: Maisey 1985; NHM P.6135, 41675.Tamiobatis: Eastman 1897A; Schaeffer 1981; Williams 1998; specimen FMNH PF5414.Tetanopsyrus: Gagnier & Wilson 1995; Gagnier et al. 1999; Hanke et al. 2001; specimens UALVP 32571,
38682, 39062, 39078, 42512, 43026, 43246, 44030, 43089.Thrinacodus: Turner 1982; Ginter 2000; Ginter & Sun 2007; Ginter & Turner 2010; Ginter et al. 2010;
Grogan & Lund 2008. Tribodus: Maisey & de Carvalho 1997; Lane 2010; Lane & Maisey 2009, 2012.Triodus: Solér-Gijon & Hampe 1998; Hampe 2003; Heidtke et al. 2004.Tristychius: Dick1978; Coates & Gess 2007; Coates & Tietjen 2018. Uraniacanthus: Bernacsek & Dineley 1977; Hanke & Davis 2008; Newman et al. 2012; Burrow et al.
2016; specimens UALVP 19259, 32448, 32469, 38679, 41669, 41857, 41858, 41862, 42095, 42095, 44046, 45366 to 45396.
Vernicomacanthus waynensis: Miles 1973a.Youngolepis: Chang & Yu 1981; Chang 1982, 1991, 2004.
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Chapter IV: Functional Morphology of Symmoriid Jaws
3. Character list
Skeletal tissues1 Tessellate calcifi ed cartilage: absent (0); present (1). Brazeau (2009); Coates & Sequeira (2001a, b);
Davis et al. (2012); Dean & Summers (2006); Dean et al. (2009); Grogan et al. (2012); Maisey (1984, 2001, 2013); Lund & Grogan (1997, 2004a, b); Seidel et al. (2016).
2 Perichondral bone: present (0); absent (1). Janvier (1996); Donoghue & Aldridge (2001); Brazeau (2009); Davis et al. (2012); Lund (1985); Coates et al. (1999).
3 Extensive endochondral ossifi cation: absent (0); present (1). Forey (1980); Gardiner (1984); Brazeau (2009); Davis et al. (2012).
4 Extensive calcifi ed cartilage: absent (0); present (1). Coates et al. (2018). 5 Dentine kind: mesodentine or semidentine (0); orthodentine (1). Donoghue et al. (2000); Brazeau
(2009); Davis et al. (2012); Burrow et al. (2016) 6 Pore canal network: absent (0); present (1). Lu et al. (2016).7 Acrodin tooth caps (enameloid cap restricted to crown apex): absent (0); present (1). Friedman &
Brazeau (2010); Zhu et al. (2009, 2013); Lu et al. (2016).
Squamation & related structures8 Trunk scales monocuspid (0); multicuspid (1). Revised after Davis et al. (2012); Burrow et al.
(2016). 9 Scale growth concentric: absent (0); present (1). Hanke & Wilson (2004); Brazeau (2009); Davis
et al. (2012); Burrow et al. (2016).10 Peg-and-socket articulation: absent (0); present (1). Gardiner (1984); Coates (1999); Brazeau
(2009); Davis et al. (2012).11 Anterodorsal process on scale: absent (0); present (1). Zhu et al. (2009, 2013); Gardiner (1984);
Coates (1999); Brazeau (2009); Davis et al. (2012).12 Body scales with bulging base: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Burrow
et al. (2016). 13 Body scales with fl attened base: absent (0); present (1). Brazeau (2009, 2012); Davis et al. (2012);
Burrow et al. (2016). 14 Body scales with basal canal or open basal vascular cavity: absent (0); present (1). Reif (1978);
Coates & Sequeira (2001a); Young (1982). 15 Neck canal: absent (0) present (1). Coates et al. (2017).16 Sensory line canal passes between or beneath scales (0); passes over scales and/ or is partially
enclosed or surrounded by scales (1); perforates and passes through scales (2). Davis (2002); Friedman & Brazeau (2010); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014); Burrow et al. (2016).
17 Lepidotrichia or lepidotrichia-like scale alignment: present (0); absent (1). Davis et al. (2012).18 Epichordal lepidotrichia: absent (0); present (1). Zhu et al. (2009, 2013).19 Fringing fulcra: absent (0); present (1). Zhu et al. (2009, 2013); Coates (1999).20 Scute-like ridge scales (fulcra): absent (0); present (1). Giles et al. (2015c).
Cranial dermal skeleton21. Sclerotic ring: absent (0); present (1). Giles et al. (2015c); Qiao et al. (2016); Zhu et al. (2016);
Burrow et al. (2016). 22 Number of sclerotic plates: four or less (0); more than four (1). Zhu et al. (2013, c170); Qiao et al.
(2016, c.241); Zhu et al. (2016, c.239); Burrow et al. (2016). 23 Dermal ornamentation: smooth (0); parallel, vermiform ridges (1); concentric ridges (2); tuber-
culate (3). Giles et al. (2015c).24 Dermal skull roof includes large dermal plates (0); consists of undifferentiated plates, tesserae
or scales (1); naked or largely scale free (2). Forey (1980); Gardiner (1984); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).
25 Cranial tessera morphology: large interlocking plates (0); microsquamose, no larger than body
squamation (1). Brazeau (2009) through to Giles et al. (2015c).26 Anterior or mesial edge of nasal notched for anterior nostril: absent (0); present (1). Contra Zhu
et al. (2013), the anterior rim of the nasal in Cheirolepis is notched.
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Chapter IV: Functional Morphology of Symmoriid Jaws
27 Supraorbital: absent (0); present (1). Zhu et al. (2009, 2013).28 Large median bone contributes to posterior margin of skull roof: absent (0); present (1). Zhu et
al. (2016).29 Medial process of paranuchal wraps around posterolateral corners of nuchal plate: absent (0);
present (1); paranuchals precluded from nuchal by centrals (2); no median bone in posterior of
skull roof (3). Giles et al. (2015c).30 Pineal opening perforates dermal skull roof: present (0); absent (1). Davis et al. (2012); Giles et
al. (2015c).31 Consolidated cheek plates: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al.
(2012); Zhu et al. (2013); Burrow et al. (2016).32 Enlarged postorbital tessera separate from orbital series: absent (0); present (1). Brazeau (2009);
Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).33 Dermal intracranial joint: absent (0); present (1). Zhu et al. (2009, 2013)34 Foramina (similar to infradentary foramina) on cheek bones: absent (0); present (1). Zhu et al.
(2009, 2013).35 Preopercular bone: absent (0); present (1). Zhu et al. (2013).36 Maxilla expanded posteriorly: absent - splint shaped (0); present - cleaver shaped (1). Zhu et al.
(2009, 2013); Lu et al. (2016).37 Sensory line network preserved as open grooves (sulci) in dermal bones (0); sensory lines pass
through canals enclosed within dermal bones (1). (Davis 2002); Davis et al. (2012); Zhu et al. (2013).
38 Sensory canal or pit-line associated with maxilla: absent (0); present (1). Friedman (2007) 39 Jugal portion of infraorbital canal joins supramaxillary canal: present (0); absent (1). Brazeau
(2009), but see redefi nition in Davis et al. (2012); Zhu et al. (2013).40 Anterior pit line of skull roof: absent (0); present (1). Giles et al. (2015c).41 Spiracular opening in dermal skull roof bounded by bones carrying otic canal: absent (0); pres-
ent (1). Giles et al. (2015); Lu et al. (2016).42 Endolymphatic ducts open in dermal skull roof: present (0); absent (1). Janvier (1996); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013); Giles et al. (2015c). 43 Dermohyal (submarginal) ossifi cation: absent (0); present (1). 44 Dermohyal (submarginal) shape: broad plate that tapers towards its proximal end (0); narrow
plate (1). Brazeau’s (2009)45 Branchiostegal series: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).46 Opercular and subopercular bones: absent (0); present (1).
47 Branchiostegal plate series along ventral margin of lower jaw: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
48 Branchiostegal ossifi cations plate-like (0); narrow and ribbon-like (1); fi lamentous (2). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Lu et al. (2016).
49 Branchiostegal ossifi cations ornamented (0); unornamented (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
50 Branchiostegals imbricated: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
51 Opercular cover of branchial chamber complete or partial (0); separate gill covers and gill slits
(1). Lund & Grogan (1997); Hanke & Wilson (2004); Davis et al. (2012); Zhu et al. (2013). 52 Gular plates: absent (0); present (1). Gardiner (1984); Brazeau (2009); Davis et al. (2012); Zhu et
al. (2013).53 Size of lateral gular plates: extending most of length of the lower jaw (0); restricted to the anteri-
or third of the jaw (no longer than the width of three or four branchiostegals) (1). Coates (1999); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
Hyoid and gill arches154 Gill skeleton mostly beneath otico-occipital region (0); mostly posterior to occipital region (1).
Zangerl (1981); Lund & Grogan (1997); Stahl (1999). 55 Perforate hyomandibula: absent (0); present (1). Zhu et al. (2009, 2013); Lu et al. (2016).56 Interhyal: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013).
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Chapter IV: Functional Morphology of Symmoriid Jaws
57 Ceratohyal smooth with posterior, lateral fossa: absent (0); present (1). Coates et al. (2018). 58 Ceratohyal anteriorly blade-shaped: absent (0), present (1). Frey et al. (in prep.). Tristychius and
Phoebodus exhibit ceratohyals with an anteriorly derived shape. 59 Hypohyals: absent (0); present (1). Friedman & Brazeau (2010); Pradel et al. (2014). 60 Basihyal absent, hyoid arch articulates directly with basibranchial (0); basihyal present (1).
Pradel et al. (2014); see also discussion in Carr et al. (2009); Brazeau et al. (2017). 61 Separate supra- and infra-pharyngobranchials absent (0); present (1). Gardiner (1984); Pradel et
al. (2014). 62 Pharyngobranchials directed anteriorly (0); posteriorly (1). Pradel et al. (2014). 63 Posteriormost branchial arch bears epibranchial unit: absent (0); present (1). Coates et al.
(2018). Absent in osteichthyans; present in chondrichthyans, Gladbachus and Acanthodes (Davis et al. 2012; Pradel et al. 2014).
64 Epibranchials bear posterior fl ange: absent (0); present (1). Coates et al. (2018). 65 Hypobranchials directed anteriorly (0); hypobranchials of second and more posterior gill arches
directed posteriorly (1). Coates et al. (2018).
Dentition & tooth-bearing bones and cartilages66 Oral dermal tubercles borne on jaw cartilages: absent (0); present (1). Hanke & Wilson (2004);
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). 67 Pharyngeal teeth or denticles: absent (0); present (1). Coates et al. (2017, 2018). 68 Tooth families/ whorls: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013).69 Bases of tooth families/ whorls: single, continuous plate (0); some or all whorls consist of sepa-
rate tooth units (1). Adjusted by Coates et al. (2018) from Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Giles et al. (2015).
70 Lingual torus: absent (0); present (1). After Ginter et al. 2010; Coates et al. (2018). 71 Basolabial shelf: absent (0); present (1). Coates et al. (2017), after Ginter et al. (2010) 72 Tooth families/whorls restricted to symphysial region (0); distributed along jaw margin (1).
Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). 73 Number of tooth families/whorls per jaw ramus: 15 or fewer (0); 20 or more (1). Coates et al.
(2018). 74 Toothplates absent (0); present (1). Follows defi nition of Coates et al. (2018). 75 Toothplate complement restricted to two pairs in the upper jaw and a single pair in the lower
jaw: absent (0); present (1). After Patterson (1965); Coates et al. (2018).76 Mandibular teeth fused to dermal plates on biting surfaces of jaw cartilages: absent (0); present
(1). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). 77 Dermal plates on biting surface of jaw cartilages: absent (0); present (1). Brazeau (2009); Davis
et al. (2012); Zhu et al. (2013); Giles et al. (2015c).78 Gnathal plates mesial to and/ or above (or below) jaw cartilage: absent (0); present (1). Zhu et
al. (2016).79 Maxilla and premaxilla sensu stricto (upper gnathal plates lateral to jaw cartilage without pala-
tal lamina): absent (0); present (1). Zhu et al. (2016).80 Dentary bone encloses mandibular sensory canal: absent (0); present (1). Gardiner (1984) and
references therein; Zhu et al. (2009, 2013).81 Infradentary foramen and groove, series: absent (0); present (1). Zhu et al. (2010).82 Tooth-bearing median rostral: absent (0); present (1). Zhu et al. (2009, 2013).83 Median dermal bone of palate (parasphenoid): absent (0); present (1). Gardiner (1984); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013).84 Denticulated fi eld of parasphenoid: without spiracular groove (0); with spiracular groove (1).
Friedman (2007); Zhu et al. (2009, 2013).85 Denticle fi eld of parasphenoid with multifi d anterior margin: absent (0); present (1). Friedman
(2007); Zhu et al. (2009, 2013); Lu et al. (2016).
Mandibular arch86 Large otic process of the palatoquadrate: absent (0); present (1). Coates & Sequeira (2001a);
Davis (2002); Brazeau (2009); Zhu et al. (2009, 2013).
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Chapter IV: Functional Morphology of Symmoriid Jaws
87 Oblique ridge or groove along medial face of palatoquadrate: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Lu et al. (2016).
88 Fenestration of palatoquadrate at basipterygoid articulation: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Lu et al. (2016).
89 Perforate or fenestrate anterodorsal (metapterygoid) portion of palatoquadrate: absent (0);
present (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).90 Articulation surface of the palatoquadrate with the postorbital process directed anteriorly (0);
laterally (1); dorsally (2). Coates et al. (2017). 91 Palatoquadrate fused to the neurocranium: absent (0); present (1). Coates et al. (2017).92 Pronounced dorsal process on Meckelian bone or cartilage: absent (0); present (1). Davis (2002);
Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016). 93 Mandibular mesial process: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al.
(2013); Burrow et al. (2016). 94 Jaw articulation located on rearmost extremity of mandible: absent (0); present (1). Davis et al.
(2012); Zhu et al. (2013).195 Dental sulcus (trough) adjacent to oral rim on Meckel’s cartilage and palatoquadrate: absent
(0); present (1). Coates et al. (2017). 96 Scalloped oral margin on Meckel’s cartilage and palatoquadrate: absent (0); present (1). Coates
et al. (2017). Characteristic of some symmoriiform chondrichthyans such as Akmonistion, Ozarcus, and Cladoselache, but also present in Helodus (pers. obs. MIC).
97 Mandibular symphysis fused: absent (0); present (1). Coates et al. (2017).
Neurocranium98 Internasal vacuities: absent (0); present (1). Lu et al. (2016). 99 Precerebral fontanelle: absent (0); present (1). Schaeffer (1981); Lund & Grogan (1997); Coates &
Sequeira (1998, 2001a, b); Maisey (2001a); Brazeau (2009); Pradel et al. (2011) Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).
100 Space for forebrain and (at least) proximal portion of olfactory tracts narrow and elongate, ex-
tending between orbits: absent (0); present (1). Coates et al. (2017).101 Prominent, pre-orbital, rostral expansion of the neurocranium: present (0); absent (1). Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013). 102 Rostral bar: absent (0); present (1). Adapted from Maisey (1985); Coates et al. (2017). 103 Internasal groove absent (0); present (1). Coates et al. (2017); present in Iniopera and Dwykasela-
chus (Pradel 2010).104 Orbitonasal lamina dorsoventrally deep: absent (0); present (1). Patterson (1965); Davis et al.
(2012); Zhu et al. (2013); Coates et al. (2017). 105 Palatobasal (or orbital) articulation posterior to the optic foramen (0); anterior to the optic
foramen, grooved, and overlapped by process or fl ange of palatoquadrate (1); anterior to optic
foramen, smooth, and overlaps or fl anks articular surface on palatoquadrate (2). Adapted by Coates et al. (2018) from Pradel et al. (2011, character 26), Coates et al. (2017, character 71) and Maisey (2005, p.61)
106 Trochlear nerve foramen anterior to optic nerve foramen: absent (0); present (1). Coates & Se-queira (2001).
107 Supraorbital shelf broad with convex lateral margin: absent (0); present (1). Coates & Sequeira (1998); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
108 Orbit directed mostly laterally and free of fl anking endocranial cartilage or bone: absent (0);
present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Coates et al. (2018). 109 Interorbital space broad (0); narrow (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013);
Coates et al. (2017).110 Optic pedicel: absent (0); present (1). Dupret et al. (2014); Zhu et al. (2009, 2013); Coates et al.
(2017).111 Ophthalmic foramen in anterodorsal extremity of orbit communicates with cranial interior:
absent (0); present (1). Coates et al. (2017).112 Extended prehypophysial portion of sphenoid: absent (0); present (1). Brazeau (2009); Davis et
al. (2012); Zhu et al. (2013).113 Canal for efferent pseudobranchial artery within basicranial cartilage: absent (0); present (1).
157
Chapter IV: Functional Morphology of Symmoriid Jaws
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).114 Entrance of internal carotids: through separate openings fl anking the hypophyseal opening or
recess (0); through a common opening at the central midline of the basicranium (1). Schaeffer (1981); Coates & Sequeira (1998); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
115 Internal carotids: entering single or paired openings in the basicranium from a posterolateral
angle (0); entering basicranial opening(s) head-on from an extreme, lateral angle (1); absent (2). Coates et al. (2017).
116 Ascending basisphenoid pillar pierced by common internal carotid: absent (0); present (1). Miles (1973b); Brazeau (2009); Friedman & Brazeau (2010); Davis et al. (2012); Zhu et al. (2013).
117 Spiracular groove on basicranial surface: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013).
118 Spiracular groove on lateral or transverse wall of jugular canal: absent (0); present (1). Davis et al. (2012); Zhu et al. (2013).
119 Spiracular groove open (0); enclosed by spiracular bar or canal (1). Lu et al. (2016), Coates et al. (2018).
120 Orbit larger than otic capsule: absent (0); present (1). Lund & Grogan (1997); Coates et al. (2017).121 Postorbital process and arcade: absent (0); present (1). Pradel et al. (2011); see also Maisey (2007)
and Coates et al. (2017). 122 Postorbital process and arcade short and deep - width not more than maximum braincase width
(excluding arcade) (0); process and arcade wide - width exceeds maximum width of braincase,
and anteroposteriorly narrow (1); process and arcade massive (2); arcade forms postorbital
pillar (3). Coates et al. (2017). 123 Postorbital process downturned, with anhedral angle relative to basicranium: absent (0); pres-
ent (1). Present in hybodontids, Acronemus (Maisey 2011) and Tristychius (Dick 1978; Coates & Tietjen 2018).
124 Jugular canal diameter small (0); large (1); canal absent (2). Pradel et al. (2011); Coates et al. (2018).
125 Canal, likely for trigeminal nerve (V) mandibular ramus, passes through the postorbital process
from proximal dorsal entry to distal and ventral exit: absent (0); present (1). (Coates et al., 2017)126 Postorbital process expanded anteroposteriorly: absent (0); present (1). (Coates et al. 2018).127 Postorbital process articulates with palatoquadrate: absent (0); present (1). Schaeffer (1981);
Coates & Sequeira (1998); Maisey (2001a); Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013). 128 Trigemino-facial recess: absent (0); present (1). Goodrich (1930); Gardiner (1984 and references
therein); Pradel (2010); Pradel et al. (2011); Davis et al. (2012). 129 Jugular canal long, extends throughout most of otic capsule wall posterior to the postorbital
process (0); short and/ or groove present on exterior of otic wall (1); absent, path of jugular re-
moved from otic wall (2). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Giles et al. (2015c); Coates et al. (2017).
130 C-bout notch separates postorbital process from supraotic shelf: absent (0); present (1). Charac-teristic feature of Tristychius, present in Acronemus (Maisey 2011).
131 Postorbital fossa: absent (0); present (1). Zhu et al. (2013).132 Hyoid ramus of facial nerve (N. VII) exits through posterior jugular opening: absent (0); pres-
ent (1). Friedman (2007); Brazeau (2009); Friedman & Brazeau (2010); Davis et al. (2012); Zhu et al. (2013).
133 Periotic process: absent (0); present (1). Maisey (2007); Coates et al. (2017).134 Articulation facet for hyomandibula: single-headed (0), double-headed (1). Zhu et al. (2009,
2013).135 Relative position of jugular groove and hyomandibular articulation: hyomandibula dorsal or
same level (i.e. on bridge) (0); jugular vein passing dorsal or lateral to hyomandibula (1). Brazeau & de Winter (2015).
136 Transverse otic process: absent (0); present (1). Lu et al. (2016); Giles et al. (2016) 137 Craniospinal process: absent (0); present (1). Giles et al. (2015); Lu et al. (2016). 138 Lateral otic process: absent (0); present (1). Schaeffer (1981); Coates & Sequeira (1998); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013). 139 Hyomandibula articulates with neurocranium beneath otic shelf: absent (0); present (1).
140 Sub-otic occipital fossa: absent (0); present (1). Coates et al. (2017, 2018).
158
Chapter IV: Functional Morphology of Symmoriid Jaws
141 Postotic process: absent (0); present (1). Pradel et al. (2011); Coates et al. (2017).142 Otic capsule extends posterolaterally relative to occipital arch: absent (0); present (1). Maisey
(1985).143 Otic capsules: widely separated (0); approaching dorsal midline (1). Coates et al. (2017).144 Otic capsules project anteriorly between postorbital processes: absent (0); present (1). Coates et
al. (2018).145 Endocranial roof anterior to otic capsules dome-like, smoothly convex dorsally and anteriorly:
absent (0); present (1). Coates et al. (2017).146 Roof of skeletal cavity for cerebellum and mesencephalon signifi cantly higher than dorsal-most
level of semicircular canals: absent (0); present (1). Coates et al. (2017).147 Roof of the endocranial space for telencephalon and olfactory tracts offset ventrally relative to
level of mesencephalon: absent (0); present (1). Coates et al. (2017).148 Labyrinth cavity separated from the main neurocranial cavity by a cartilaginous or ossifi ed
capsular wall (0); skeletal medial capsular wall absent (1). Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013).
149 Double octaval nerve foramena in chondrifi ed mesial wall of otic capsule: absent (0); present
(1). Coates et al. (2018). 150 External (horizontal) semicircular canal joins the vestibular region dorsal to posterior ampulla
(0); joins level with posterior ampulla (1). Davis et al. (2012); Zhu et al. (2013).151 Angle of external semicircular canal: in lateral view, straight line projected through canal in-
tersects anterior ampulla, external ampullae, and base of foramen magnum: absent (0); present
(1). Coates et al. (2017).152 Left and right external semicircular canals approach or meet the posterodorsal midine of the
hindbrain roof: absent (0); present (1). Coates et al. (2017).153 Preampullary portion of posterior semicircular canal absent (0); present (1). Coates et al. (2017). 154 Crus commune connecting anterior and posterior semicircular canals present (0); absent (1).
Coates et al. (2017). 155 Sinus superior: absent or indistinguishable from union of anterior and posterior canals with
saccular chamber (0); present, elongate and nearly vertical (1). Davis et al. (2012); Zhu et al. (2013).
156 Lateral cranial canal: absent (0); present (1). Zhu et al. (2009, 2013); Lu et al. (2016). 157 Endolymphatic ducts: posteriodorsally angled tubes (0); tubes oriented vertically through endo-
lymphatic fossa/posterior dorsal fontanelle (1). Schaeffer (1981); Coates & Sequeira (1998, 2001); Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
158 Posterior dorsal fontanelle connected to persistent otico-occipital fi ssure (0); posterior tectum
separates fontanelle from fi ssure (1). Schaeffer (1981); Coates & Sequeira (1998); Pradel et al. (2011).
159 Subcircular endolymphatic foramen: absent (0); present (1). Pradel et al. (2015), Coates et al. 2017.
160 External opening for endolymphatic ducts anterior to crus commune: absent (0); present (1). Coates et al. (2017).
161 Supraotic shelf broad: absent (0); present (1). Coates et al. (2017).162 Dorsal otic ridge: absent (0); present (1). Coates & Sequeira (1998, 2001); Maisey (2001); Davis
(2002); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).163 Dorsal otic ridge forms a crest posteriorly: absent (0); present (1). Coates & Sequeira (1998,
2001); Pradel et al. (2011).164 Endolymphatic fossa: absent (0); present (1). Pradel et al. (2011). 165 Endolymphatic fossa elongate (slot-shaped), dividing dorsal otic ridge along midline: absent (0);
present (1). Coates et al. (2017). 166 Perilymphatic fenestra within the endolymphatic fossa: absent (0); present (1). Pradel et al.
(2011); Coates et al. (2017).167 Ventral cranial fi ssure: absent (0); present (1). Janvier (1996); Coates & Sequeira (2001); Maisey
(2001); Davis (2002); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013).168 Endoskeletal intracranial joint: absent (0); present (1). Janvier (1996); Davis et al. (2012); Zhu et
al. (2013).169 Metotic (otic-occipital) fi ssure: absent (0); present (1). Schaeffer (1981); Janvier (1996); Coates
159
Chapter IV: Functional Morphology of Symmoriid Jaws
& Sequeira (1998); Maisey (2001); Davis (2002); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Zhu et al. (2013).
170 Vestibular fontanelle: absent (0); present (1). Brazeau (2009); Friedman & Brazeau (2010). Davis et al. (2012); Zhu et al. (2013).
171 Hypotic lamina: absent (0); present (1). Schaeffer (1981); Maisey (1984, 2001); Brazeau (2009); Pradel et al. (2011, 2013); Davis et al. (2012); Zhu et al. (2013); Coates et al. (2017).
172 Glossopharyngeal nerve path: directed laterally, across fl oor of the saccular chamber and exits
via foramen in side wall of the otic capsule (0); directed posteriorly, and exits through metotic
fi ssure or foramen in posteroventral wall of otic capsule (1); exits laterally through a canal con-
tained ventrally (fl oored) by the hypotic lamina (2); exits through a foramen anterior to the pos-
terior ampulla (3). Coates et al. (2017), adapted from Schaeffer (1981); Coates & Sequeira (1998, 2001); Brazeau (2009): Davis et al. (2012); Zhu et al. (2013); Pradel et al. (2011, 2013).
173 Glossopharyngeal and vagus nerves share common exit from neurocranium: absent (0); present
(1). Coates et al. (2017).174 Basicranial morphology: platybasic (0); tropibasic (1). Brazeau (2009); Pradel et al. (2011); Davis
et al. (2012); Zhu et al. (2013). 175 Channel for dorsal aorta and/or lateral dorsal aortae passes through basicranium (0): exter-
nal to basicranium (1). Schaeffer (1981); Coates & Sequeira (1998); Brazeau (2009); Pradel et al. (2011); Brazeau & Friedman (2014); Coates et al. (2017).
176 Dorsal aorta divides into lateral dorsal aortae posterior to occipital level (0); anterior to level of
the occiput (1). Pradel et al. (2011); Giles et al. (2015); Coates et al. (2017).177 Ventral portion of occipital arch wedged between rear of otic capsules: absent (0); present (1).
Schaeffer (1981); Coates & Sequeira (1998); Maisey (2001a); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Coates et al. (2017).
178 Dorsal portion of occipital arch wedged between otic capsules: absent (0); present (1). Schaeffer (1981); Coates & Sequeira (1998); Maisey (2001a); Brazeau (2009); Pradel et al. (2011); Davis et al. (2012); Coates et al. (2017).
179 Occipital crest anteroposteriorly elongate, and extends from the roof of the posterior tectum:
absent (0); present (1). Coates et al. (2018).
Axial and appendicular skeleton180 Calcifi ed vertebral centra: absent (0); present (1). Maisey (1985); Coates et al. (2017).181 Chordacentra: absent (0); present (1). Stahl (1999); Coates and Sequeira (2001); Coates et al.
(2017). 182 Chordacentra polyspondylous and consist of narrow closely packed rings: absent (0); present
(1). Derived from Patterson (1965); Coates et al. (2017).183 Synarcual: absent (0); present (1). Stahl (1999); Brazeau (2009); Davis et al. (2012); Zhu et al.
(2013); Coates et al. (2017).184 Macromeric dermal pectoral girdle (0); micromeric or lacking dermal skeleton entirely (1).
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).185 Macromeric dermal pectoral girdle composition: ventral and dorsal components (0); ventral
components only (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).186 Macromeric pectoral dermal skeleton forms complete ring around the trunk: present (0); ab-
sent (1). Goujet & Young (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).187 Median dorsal plate: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).188 Scapular process (dorsal) of shoulder endoskeleton: absent (0); present (1). Coates & Sequeira
(2001a); Zhu & Schultze (2001); Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).
189 Ventral margin of separate scapular ossifi cation: horizontal (0); deeply angled (1). Hanke & Wilson (2004); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).
190 Cross sectional shape of scapular process: fl attened or strongly ovate (0); subcircular (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).
191 Flange on trailing edge of scapulocoracoid: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).
192 Scapular process with posterodorsal process: absent (0); present (1). Coates & Sequeira (2001a); Davis et al. (2012); Zhu et al. (2013).
160
Chapter IV: Functional Morphology of Symmoriid Jaws
193 Mineralisation of internal surface of scapular process: mineralised all around (0); un-min-
eralised on internal face forming a hemicylindrical cross-section. Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Burrow et al. (2016).
194 Coracoid process: absent (0); present (1). Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).195 Procoracoid mineralisation: absent (0); present (1). Davis (2002); Hanke & Wilson (2004): Brazeau
(2009).196 Fin base articulation on scapulocoracoid: stenobasal, deeper than wide (0); eurybasal, wider
than deep (1). Lu et al. (2016).197 Pectoral fi n articulation monobasal (0); dibasal (1); three or more basals (2).
198 Metapterygium pectinate subtriangular plate or bar supporting numerous (six or more) radials
along distal edge: absent (0); present (1). Coates et al. (2018).199 Metapterygial whip: absent (0); present (1). Coates et al. (2017).200 Biserial pectoral fi n endoskeleton: absent (0); present (1). Lu et al. (2016).201 Propterygium perforated: absent (0); present (1). Rosen et al. (1981); Patterson (1982); Davis et
al. (2012); Zhu et al. (2013).202 Pelvic girdle with fused puboischiadic bar: absent (0); present (1). Maisey (1984); Coates & Se-
queira (2001a); Coates et al. (2017).203 Mixipterygial/ mixopterygial claspers: absent (0), present (1). Coates & Sequeira (2001a, b);
Brazeau & Friedman (2014). 204 Pre-pelvic clasper or tenaculum: absent (0); present (1). After Patterson (1965); Coates et al.
(2017).205 Number of dorsal fi ns, if present: one (0); two (1); one, extending from pectoral to anal fi n level
(2). Coates & Sequeira (2001a); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013).206 Brush complex of bilaterally distributed calcifi ed tubes fl anking or embedded in calcifi ed carti-
lage core: absent (0); present (1). Coates et al. (2017, 2018)207 Posterior or pelvic-level dorsal fi n with calcifi ed base plate: absent (0); present (1). Coates &
Sequeira (2001a, b). 208 Posterior dorsal fi n with delta-shaped cartilage: absent (0); present (1). Coates & Sequeira (2001a,
b). 209 Posterior or pelvic-level dorsal fi n shape, base approximately as broad as tall and not broader
than other median fi ns (0); base much longer than fi n height, substantially longer than other
median fi ns (1). Brazeau & deWinter (2015); Lu et al. (2017). 210 Anal fi n: absent (0); present (1). Coates & Sequeira (2001); Brazeau (2009); Davis et al. (2012);
Zhu et al. (2013).211 Anal fi n base narrow, posteriormost proximal segments radials broad: absent (0); present (1).
Heidtke (1999). 212 Caudal radials restricted to axial lobe (0); extend beyond level of body wall and deep into hypo-
chordal lobe (1). Davis et al. (2012); Zhu et al. (2013). 213 Caudal neural and/or supraneural spines or radials short (0); long, expanded, and supporting
high aspect-ratio (lunate) tail with notochord extending to posterodorsal extremity (1); noto-
chord terminates pre-caudal extremity, neural and heamal radial lengths near symmetrical and
support epichordal and hypochordal lobes respectively (2). Coates & Sequeira (2001a, b).
Spines: fi ns, cranial and elsewhere214 Dorsal fi n spine or spines: absent (0); present (1). Zhu et al. (2001); Zhu & Yu (2002); Friedman
(2007); Brazeau (2009); Davis et al. (2012); Zhu et al. (2013); Lu et al. (2016). 215 Dorsal fi n spine at anterior (pectoral level) location only: absent (0); present (1). Coates & Sequei-
ra (2001a); Ginter et al. (2010). 216 Dorsal fi n spine cross section: horseshoe shaped (0); fl at sided, with rectangular profi le (1); sub-
circular (2). Hampe (2003); Brazeau & de Winter (2015).217 Anterior dorsal fi n spine leading edge concave in lateral view: absent (0); present (1). Lund
(1985, 1986).218 Anal fi n spine: absent (0); present (1). Maisey (1986); Davis (2002); Brazeau (2009).219 Pectoral fi n spines: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al. (2012); Zhu
et al. (2013).220 Pectoral fi n spine with denticles along posterior surface: absent (0); present (1). Burrow et al.
161
Chapter IV: Functional Morphology of Symmoriid Jaws
(2016).221 Prepectoral fi n spines: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009); Davis et al. (2012); Zhu et al. (2013). Present in Doliodus (Maisey et al. 2017).222 Admedian pectoral spines absent (0); present (1). Burrow et al. (2016); see also description of
Doliodus pectoral girdle (Maisey et al. 2017).223 Median fi n spine insertion: shallow, not greatly deeper than dermal bones/ scales (0); deep (1).
Davis (2002); Hanke & Wilson (2004); Brazeau (2009). Davis et al. (2012); Zhu et al. (2013).224 Intermediate (pre-pelvic) fi n spines: absent (0); present (1). Davis (2002); Hanke & Wilson (2004);
Brazeau (2009); Davis et al. (2012); Zhu et al. (2013). 225 Fin spines with ridges: absent (0); present (1). Davis (2002); Brazeau (2009); Davis et al. (2012);
Zhu et al. (2013).226 Fin spines with nodes: absent (0); present (1). Davis (2002); Hanke & Wilson (2004); Brazeau
(2009). Davis et al. (2012); Zhu et al. (2013).227 Fin spines (dorsal) with rows of large denticles: absent (0); on posterior surface (1); on lateral
surface (2). Maisey (1989b); Davis et al. (2012); Zhu et al. (2013); Brazeau & Friedman (2014).228 Cephalic spines: absent (0); present (1). Maisey (1989); Coates et al. (2017)
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165
Chapter IV: Functional Morphology of Symmoriid Jaws
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CONCLUSIONS
169
Conclusions
Alpha diversity and palaeoecology of
the Maïder region of Morocco
Fammenian Fossillagerstätten of the Maïder re-gion contain numerous gnathostome remains of at least one sarcopterygian species, one actinoptery-gian species, four species of placoderms and fi ve species of chondrichthyans. Most of these gnatho-stome remains were excavated from the Thylaco-cephalan Layer, an argillaceous interval of about two meter thickness with numerous small nodules containing mostly carapaces of thylacocephalan arthropods. This layer represents a Konservat-La-gerstätte (conservation deposit; see Chapter II). In this chapter I, I analysed the faunal composition, trophic nucleus, alpha diversity and ecospace oc-cupation of 21 invertebrate associations of early Famennian (17 from Madene el Mrakbib) to mid-dle Tournaisian age (4 from Aguelmous). The spe-cies richness fl uctuated mostly between three and 14 taxa (rarely it comprised up to 24 taxa) and the ecospace occupation fl uctuated between one and 12 three-dimensional modes of life. Within the ecospace, the ratio between pelagic and benthic modes of life varied signifi cantly. In the trophic nucleus, there were mostly pelagic but also some benthic taxa.
The mostly relatively low taxonomic di-versity and the dominance of pelagic or benthic taxa tolerating dysoxic conditions show that the environment of the Famennian and Tournaisian was characterised by often oxygen-depleted bot-tom-waters in the Maïder Basin (at least in the studied localities). Some of the fl uctuations in ecospace occupation and species richness cor-relate with Famennian and Tournaisian bio-events of varying importance and changes in regional or global sea level including the consequences for oxygen supply to bottom waters. Since the fl ucta-tions in the associations in combination with the changes in the sediment (varying content of clay and carbonate), fi t reasonably well with the glob-al sea level curves, the regional sea level curve of the Maïder was probably more fl uctuant than reported by previous studies. The Famennian eco-space was also more depleted after the Kellwass-er Event (late Frasnian) and during the Annulata Event (middle Famennian). In general, the envi-ronment in which the gnathostomes of the Maïder lived was not suitable for a highly diverse ecosys-tem (common hypoxic to dysoxic conditions, low taxonomic richness, scarcity of benthos, several bio-events), which is also shown by the relatively low diversity of jawed fi sh (around 8, possibly 10 species) and the complete lack of benthic gnatho-
stomes (in the neighbouring Tafi lalt region, teeth of 17 chondrichthyan taxa including pelagic and benthic taxa occur). The chondrichthyans of the Maïder are most abundant in the Thylacocephalan Layer with thylacocephalans as an important food source.
Taphonomy of the Moroccan Fossillag-
erstätte
The mineral composition of fossils of some De-vonian Fossillagerstätten of the eastern Anti-At-las was analysed. Cephalopods, thylacoephalan and vertebrate skeletal remains contain calcite, goethite and sometimes haematite. Bones of plac-oderms and the cartilage of chondrichthyans are preserved in hydroxyapatite and, muscle fi bres of the chondrichthyans contain goethite and hae-matite among other iron minerals; these fossils were likely primarily preserved in pyrite that later weathered into iron oxides and hydroxides.
The occurrence of iron oxides and hydrox-ides (and possibly primary pyrite), the clayey fa-cies and the few benthic invertebrate taxa (ben-thic chondrichthyans are completely absent) in the gnathostome bearing Thylacopehalan Layer suggests that the fossils were embedded under ox-ygen-depleted conditions. These low oxygen-con-ditions might have been caused by the limited water exchange due to the restricted palaeogeog-raphy of the Maïder Basin, which was bordered by land and two pelagic submarine ridges.
Because of the often exceptional fossil pres-ervation (including soft-tissue in, e.g., chondrich-thyans), the faunal composition (few benthos), the abundance of primary pyrite and phosphates and the palaeogeography of the Maïder region, the Famennian Thylacocephala Layer represents the fi rst Devonian Konservat-Lagerstätte of North Africa.
Famennian chondrichthyans of the
Famennian Konservat-Lagerstätte of
the Maïder
Two of the at least fi ve chondrichthyan species discovered in the Famennian Konservat-Lager-stätte were described in the framework of this the-sis. The Famennian Phoebodus saidselachus sp. nov. is the fi rst Phoebodus specimen preserving body remains (Chapter III). Before this discovery,
170
Conclusions
this well-known geographically widely distribut-ed Devonian taxon was exclusively based on teeth and tentatively assigned isolated fi n spines. The anatomy of Phoebodus saidselachus sp. nov. and of the stratigraphically younger phoebodont Thr-inacodus gracia (Carboniferous of Bear Gulch) show that phoebodontids are a chondrichthyan clade characterised by slender and elongate eel-shaped bodies. In the more derived genus Thrina-codus, the degree of elongation is more extreme than in Phoebodus, which corroborates earlier assumptions on the phylogenetic relationships between the two genera based on teeth. Addition-ally, the phylogenetic analyses confi rmed that the Phoebodontidae are stem elasmobranchs, which encompasses both genera. Since phoebodontid teeth are known from the Givetian (Middle Devo-nian), the phoebodontids and in particular Phoe-bodus represent the earliest stem elasmobranchs and also the oldest anguilliform chondrichthyans.
The second chondrichthyan described from the Fossillagerstätte of the Maïder is the sym-moriiform Ferromirum oukherbouchi gen. et sp. nov (Chapter IV). It is a single specimen with preserved body outline and visceral skeleton, shoulder girdles and fi n spine in three-dimension-al preservation. The virtual 3D-reconstruction of the specimen revealed that this specimen has the best preserved jaws of symmoriiform chondrich-thyans currently known. Based on mechanical
experiments with 3D-prints, the jaw function of a symmoriid could be reconstructed for the fi rst time. Due to the confi guration of the articulation, the lower jaw rotated laterally outward when the mouth opened. As a result of this lateral rotation, more teeth became exposed and thus functional than originally thought. In contrast to the apheto-hyoidean hypothesis (no suspensory function of the hyoid) where a gap exists between the jaws and branchial arches, the hyoid and ceratohyal are tightly articulated with the jaws in Ferromirum. Therefore, the hyoid functioned as a suspension between the jaws and the neurocranium. The jaw function mentioned above and the suspensory function of the hyoid might have been common in symmoriiforms as their jaw-to-skull articulation is a conservative feature in these chondrichthyans (as has been shown by the perfect fi t of the up-per jaws of Ferromirum to the neurocranium of Dwykaselachus).
To conclude, the chondrichthyans preserved in nodules of the Famennian Konservat-Lager-stätte of the Maïder Basin provided new insights into the morphological disparity of Devonian chondrichthyans (in the case of Phoebodus said-selachus sp. nov) and they also allow us to recon-struct the function of certain skeletal elements (suc h as in Ferromirum oukherbouchi gen. et sp. nov.).
APPENDIX A
Collaborations with other projects
(abstracts)
173
Appendix A
THE OLDEST GONDWANAN CEPHALOPOD
MANDIBLES (HANGENBERG BLACK SHALE, LATE
DEVONIAN) AND THE MID-PALAEOZOIC RISE OF
JAWS
by CHRISTIAN KLUG1 , LINDA FREY1 , DIETER KORN2 , ROMAIN JATTIOT1 and
MARTIN R €UCKLIN3
1Pal€aontologisches Institut und Museum, Universit€at Z€urich, Karl Schmid-Strasse 4, CH-8006, Z€urich, Switzerland; [email protected], [email protected],
[email protected] f€ur Naturkunde Berlin, Leibniz-Institut f€ur Evolutions- und Biodiversit€atsforschung, Invalidenstraße 43, D-10115, Berlin, Germany;
[email protected] Biodiversity Center, Postbus 9517, 2300 RA, Leiden, The Netherlands; [email protected]
Typescript received 4 April 2016; accepted in revised form 3 June 2016
Abstract: It is widely accepted that the effects of global
sea-level changes at the transition from the Devonian to the
Carboniferous are recorded in deposits on the shelf of north-
ern Gondwana. These latest Devonian strata had been
thought to be poor in fossils due to the Hangenberg mass
extinction. In the Ma’der (eastern Anti-Atlas), however, the
Hangenberg Black Shale claystones (latest Famennian) are
rich in exceptionally preserved fossils displaying the remains
of non-mineralized structures. The diversity in animal
species of these strata is, however, low. Remarkably, the
organic-rich claystones have yielded abundant remains of
Ammonoidea preserved with their jaws, both in situ and iso-
lated. This is important because previously, the jaws of only
one of the main Devonian ammonoid clades had been found
(Frasnian Gephuroceratina). Here, we describe four types of
jaws of which two could be assigned confidently to the
Order Clymeniida and to the Suborder Tornoceratina. These
findings imply that chitinous normal-type jaws were likely to
have already been present at the origin of the whole clade
Ammonoidea, i.e. in the early Emsian (or earlier). Vertebrate
jaws probably evolved prior to the origin of ammonoids, in
the Early Devonian. The temporal succession of evolutionary
events suggests that it could have been the indirect positive
selection pressure towards strong (and thus preservable) jaws
since defensive structures of potential prey animals would
otherwise have made them inaccessible to jawless predators
in the course of the mid-Palaeozoic marine revolution. In
this respect, our findings reflect the macroecological changes
that occurred in the Devonian.
Key words: Cephalopoda, Ammonoidea, mass extinctions,
macroecology, Devonian, Morocco.
[Palaeontology, 2016, pp. 1–19]
174
Appendix A
�������������� �������������� ���� �
�������� �� ������ �������������� ����������� �� ������� ������ ��
During the Palaeozoic, a diversification in modes of life occurred that included a wide range of predators. Major
macroecological events include the Cambrian Explosion (including the Agronomic Substrate Revolution and the here
introduced ‘Ediacaran-Cambrian Mouthpart Armament’), the Great Ordovician Biodiversification Event, the
Palaeozoic Plankton Revolution, the Siluro-Devonian Jaw Armament (newly introduced herein) and the Devonian
Nekton Revolution. Here, we discuss the evolutionary advancement in oral equipment, i.e. the Palaeozoic evolution of
mouthparts and jaws in a macroecological context. It appears that particularly the latest Neoproterozoic to Cambrian and
the Silurian to Devonian were phases when important innovations in the evolution of oral structures occurred. • Key
words: Gnathostomata, Cephalopoda, evolution, convergence, diversity, nekton, jaws.
CHRISTIAN KLUG, LINDA FREY, ALEXANDER POHLE, KENNETH DE BAETS & DIETER KORN 2017. Palaeozoic evolu-
tion of animal mouthparts. Bulletin of Geosciences 92(4), 511–524 (4 figures, 1 table). Czech Geological Survey,
Prague. ISSN 1214-1119. Manuscript received November 10, 2016; accepted in revised form September 22, 2017; pub-
lished online December 6, 2017; issued December 31, 2017.
Christian Klug, Linda Frey & Alexander Pohle, Paläontologisches Institut und Museum, Universität Zürich, Karl
Schmid-Strasse 4, 8006 Zürich, Switzerland; [email protected], [email protected], [email protected]
• Kenneth De Baets, GeoZentrum Nordbayern, Fachgruppe PaläoUmwelt, Universität Erlangen, Loewenichstr. 28,
91054 Erlangen, Germany; [email protected] • Dieter Korn, Museum für Naturkunde, Leibniz-Institut für Evolu-
tions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany; [email protected]
APPENDIX B
Additional article published during doctoral studies
Intraspecifi c variation in fossil vertebrate populations: Fos-
sil killifi shes (Actinopterygii: Cyprinodontiformes) from the
Oligocene of the Central Europe
Linda Frey, Erin E. Maxwell and Marcelo R. Sánchez-Villagra
Published in: Palaeontologia Electronica, 19.2.14A: 1-27
palaeo-electronica.org/content/2016/1464-fossil-killifi shes-from-europe
177
Appendix B
Palaeontologia Electronica
Palaeontologia Electronica
Prolebias rhenanus
Pr. stenoura
Paralebias cephalotes
Prolebias
Paralebias Prolebias
Paralebias cephalotes.
Prolebias Prolebias
Paralebias
178
Appendix B
Prolebias rhenanus
Pr. stenoura
Paralebias cephalotes
Pa. cephalotes
179
Appendix B
Kenyaichthys
kipkechi Kenyaichthy;
Thaumaturus
intermedius,
Atractosteus
messelensis
Lepisosteus
bemisi,
Atractosteus
simplex, A.
messelensis, A.
atrox, Cuneatus
cuneatus,
Cuneatus wileyi
Amyzon
aggregatum
Scaumenacia
curta
Semionotus
Semionotus
Gasterosteus
doryssus
Kerocottus
divaricatus
K. pontifex,
K. hypoceras,
Kerocottus
Myoxocephalus
idahoensis
180
Appendix B
Prolebias
rhenanus Pr. stenoura
Paralebias cephalotes
Paralebias cephalotes
181
Appendix B
Prolebias rhenanus
Pr. stenoura Paralebias cephalotes
182
Appendix B
Prolebias rhenanus
Prolebias
rhenanus
Prolebias
stenoura
Prolebias stenoura
Para-
lebias cephalotes
Paralebias cephalotes
Pa. cephalotes
Prolebias rhenanus Pr stenoura Paralebias cephalotes
Prolebias rhenanus Prolebias stenoura
(n = 40)
Paralebias cephalotes
183
Appendix B
Prolebias sten-
oura
Problebias rhenanus
Paralebias cephalotes
Pro-
lebias rhenanus Pr. stenoura Paralebias cephalotes
184
Appendix B
Prolebias rhenanus Pr. stenoura Paralebias cephalotes
185
Appendix B
Prolebias rhenanus
P
P
Prolebias stenoura
P
P
Paralebias cephalotes
P
P
Prolebias rhenanus
S
P
Prolebias rhenanus Prolebias stenoura Paralebias cephalotes
186
Appendix B
S P
S P S P S
P
S
P
Prolebias stenoura
S P
S P
Paralebias cephalotes
S P
S P
S
Prolebias rhenanus.
Prolebias stenoura.
187
Appendix B
S P
Prolebias
Pr. stenoura
Pr. stenoura
Pr. rhenanus
Para-
lebias cephalotes Prolebias
Paralebias
Prolebias
Pa. cephalotes
Pa. cephalotes
P Pr. stenoura
P
Paralebias cephalotes
Prolebias
Pr. rhenanus Pr. sten-
oura
Paralebias cephalotes.
188
Appendix B
Prolebias rhenanus Paralebias cepha-
lotes
Pr. stenoura
Problebias
Prolebias Prolebias
rhenanus P Pr.
stenoura P
Paralebias cephalotes P
Pro-
lebias
Prolebias rhenanus
Pr. stenoura
Gambusia quadruncus
Xenoophorus
Gambusia,
189
Appendix B
Paralebias
Prolebias
Recherches sur les poissons
fossiles.
Biological Journal of the Linnean Society,
Galaxias platei. Journal of Fish Biology,
Canadian Journal of Earth Science,
Copeia,
Paleobiology,
Paleobiol-
ogy,
Gasterosteus
doryssus Paleobiology,
Systematic Zoology,
Alioramus altai
PLoS ONE
, Danio
rerio Developmental
Dynamics,
Paleobiology,
Copeia,
Paleobiology,
Lucania parva
190
Appendix B
The Southwestern Naturalist
Scaumenacia curta
Geodiversitas,
Salvelinus alpinus
International Journal of
Zoology,
Journal of Biogeography
Zoological Journal of
the Linnean Society
Vertebrate Zoology,
Paleobiology,
Aphanius
Folia Zoologica
Lebias fasciata
Italian Journal of Zoology
Aphanius fasciatus
Journal of Fish Biology
Evolution and Development,
Xenoophorus
Occasional Papers of the
Museum of Zoology,
PLoS ONE
Nature,
Evolution,
Aus-
trolebias
Biological Journal of the
Linnean Society
Géobios,
Prolebias
rhenanus Sciences géologique Bulletin,
Comptes rendus de
l`Académie des Sciences Paris
Aphanius
Prolebias egeranus Journal of the
National Museum (Prague), Natural History Series
Prolebias stenoura
Pro-
lebias
Geodiversitas,
Paralebias Neues
Jahrbuch für Geologie und Paläontologie Abhand-
lung,
Bulletin du Service de la Carte
géologique de France,
Bulletin du Bureau de Recherche
géologique minière,
Philosophical Transactions of the Royal Society B,
Copeia
191
Appendix B
Society
of Vertebrate Paleontology Memoir,
Developmental
Dynamics,
Variation: A Cen-
tral Concept in Biology
Palaeontologia Electronica
Ecology Letters,
Journal of Paleontology,
Evolution,
Fishes of the Great
Lakes region
Lucania parva
Miscellaneous Publications, Museum
of Zoology, University of Michigan
Paleobiology,
Pale-
obiology,
Paleobiology,
Science,
Bulletin of the Japanese Society of Scientific Fisher-
ies,
Manticoceras
Cephalopods Present and Past: New Insights and
Fresh Perspectives.
Dikelocephalus
Journal
of Paleontology,
Journal of Paleontol-
ogy,
Gambusia quadruncus
Journal of Fish Biology
Progonomys
Paleobiology,
Journal of the Fisheries Research Board of Canada,
Fish Physiology Volume XI-B
Neues Jahrbuch
der Geologie und Paläontologie Abhandlungen,
The Evolution of Perisso-
dactyls.
Onohippidium
Journal of Vertebrate Paleon-
tology,
Salmo gaird-
neri Environmental Biology of Fishes,
Aphanius fasciatus
Oceanologica Acta,
Journal of Experimental Zoology
(Molecular and Developmental Evolution),
Paleobi-
ology,
192
Appendix B
BMC Evolutionary
Biology,
Animal Species and Evolution.
Oecologia,
Semionotus
Evolution,
Paleobiology,
Environmental Biology of
Fishes,
Integrative
and Comparative Biology,
Agaricocrinus
Journal of Paleontology,
Mesozoic Fishes 3 - Systematics,
Paleoenvironments and Biodiversity.
Feuille des Jeunes Naturalists, 23e année
(1892-1893)
Acrochordiceras
Palae-
ontology,
Coregonus lavaretus Acta
Biologica Cracoviensia Series Zoologia,
Fishes of the World
Aphanius fasciatus
Copeia
Revue des Sciences naturelles
d`Auvergne,
Paleo-
biology,
Syntarsus rhodesiensis
Dinosaur Systematics:
Approaches and Perspectives.
Aphanius Prolebias
Journal of Morphology
Notho-
branchius PLoS
ONE
Evolution,
Bulletin de la Société d`Histoire
naturelle de Toulouse,
Evolutionary Biology,
Pun-
gitius pungitius Biological Journal of the Linnean
Society,
The Major Features of Evolution.
Palaios,
Journal of the Fisheries Research Board of
Canada
Aphanius fasciatus
Nova Thalassia
Aphanius fasciatus
Animalia
Aphanius fasciatus
Italian Journal of Zoology
Aphanius fasciatus
Journal of Morphology
Integrative and Comparative Biology,
193
Appendix B
Zoology,
American Zoologist,
Science
Olenellus gilberti
Journal of
Systematic Palaeontology
Acta Zoologica,
Evolutionary Ecology
Menidia
Copeia,
Bio-
logical Journal of the Linnean Society,
194
Appendix B
Prolebias rhenanus
195
Appendix B
196
Appendix B
Prolebias stenoura
197
Appendix B
Paralebias
cephalotes
198
Appendix B
199
Appendix B
200
Appendix B
201
Appendix B
203
ACKNOWLEDGMENTS
205
Acknowledgments
I would like to show my greatest appreciation to my supervisor Prof. Dr. Christian Klug (University of Zurich) for his support, patience and encouragements and for sharing his knowledge about the palaeon-tology of Morocco during the work on my dissertation. Without his guidance, this dissertation would not have been possible.
I greatly thank Prof. Dr. Michael Coates (University of Chicago) and Dr. Martin Rücklin (Naturalis Bio-diversity Center, Leiden) for accepting to be committee members and for the illuminating discussions, inputs and feedbacks. Many thanks go to Prof. Dr. Marcelo Sánchez and to Prof. Dr. Hugo Bucher for providing me work space and constructive feedbacks during committee meetings.
During this dissertation, I received generous support from many colleagues and therefore, I would like to thank:
The colleagues of the Ministère de l’Energie, des Mines, de l’Eau et de l’Environnement (Direction du Développement Minier, Division du Patrimoine, Rabat, Morocco) for providing working and sample export permits,
Said Oukherbouch (Tafraoute, Morocco) for his enormously important help and support during fi eld work,
Michał Ginter (University of Warsaw) and Vachik Hairapetian (Islamic Azad University of Isfahan) for sharing their knowledge o n early chondrichtyan teeth,
René Kindlimann (Aathal) and Jorge Carrillo-Briceño (University of Zurich) for sharing their exper-tise on fossil and recent cartilagenous fi sh,
Dieter Korn (Museum für Naturkunde, Berlin) for sharing his knowledge on the diversity of Devo-nian ammonoids, for providing data for palaeoecological analyses and for giving constructive feed-backs,
Michael R. W. Amler (University of Cologne) for helping in the determination of Devonian bivalves, Per Ahlberg (University of Uppsala) for advice about 3D-reconstruction software, Christina Brühwiler (Winterthur), Ben Pabst (Zurich), Claudine Misérez (Neuchâtel) and the Tahiri
Museum (Erfoud) for their excellent fossil preparation, Rosi Roth (University of Zurich) for preparing fossil material and for helping in the photo lab. Markus Hebeisen (University of Zurich) for providing working space in his preparation lab and for
introducing me into preparation with airscribes, Alexander Pohle (University of Zurich) for conducting XRD-analyses, Lydia Zehnder and Sebastian Cionoiu (both ETH Zurich) for their generous help with the XRD- and
Raman-analyses, Iwan Jerjen (ETH Zurich), Tom Davis (University of Bristol), Alexandra Wegemann (University of
Zurich) and Anita Schweitzer (Zurich) for acquiring computer tomography scans of the specimens, Thodoris Argyriou (Paris) for sharing his knowledge about fi shes, for CT-scanning and assisting
during virtual 3D-reconstruction, Amane Tajika (NHM, New York) and Tobias Reich (University of Zurich) for kindly providing help
during segmentation of CT-scans, Gabriel Aguirre-Fernández (University of Zurich) for introducing me into software used for phyloge-
netic analysis, Morgane Brosse (Zurich) for generously helping me to solve any problem concerning the layout of
this disseration, and Heike Götzmann as well as Heinrich Walter (both University of Zurich) for their administrative and
technical support.
I would also like to thank all the colleagues of the Palaeontological Institute and Museum of the Univer-sity of Zurich not only for their scientifi c advices and support but also for their friendship. Moreover, I would like to show my appreciation to the people I met in Morocco for their hospitality, which made our fi eld trips very pleasant.
A big thank you goes to my family, especially to my parents Edith and Peter and to my grandmother Ma-rie Anne who always supported me during my studies.
206
Acknowledgments
Funding
I greatly appreciate the fi nancial support of this dissertation by the Swiss National Science Founda-tion (No. 200021_156105)
The Swiss Geological Society supported the participation at 14th International Symposium on Early and Lower Vertebrates in Poland in 2017.
207
CURRICULUM VITAE
208
Curriculum Vitae
Name: FreyFirst name: LindaDate of birth: 10.07.1987Nationality: SwissHeimatort: St. Ursen (FR)
Education
2003 –2007 Kantonsschule Wettingen
2007 –2011 University of Zurich, Bachelor of Science Main subject: Biology
2012 –2013 University of Zurich, Master of ScienceMaster thesis in Palaeontology:Alpha diversity and palaeoecology of invertebrate associations of the Early Devonian in the Moroccan Anti-Atlas (Grade: 5.7) Supervisor: Prof. Dr. Christian Klug
Since 2014 PhD student in Palaeontology Palaeontological Institute and Museum, University of Zurich Supervisor: Prof. Dr. Christian Klug
Publications during doctoral studies
Articles
Frey, L., Rücklin, M., Korn, D. and Klug, C. (2018): Late Devonian and Early Carboniferous alpha diversity, ecospace occupation, vertebrate assemblages and bio-events of southeastern Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology, 496 (1): 1-17;
Klug, C., Frey, L., Pohle, A., De Baets, K. and Korn, D. (2017): Palaeozoic evolution of animal mouthparts. Bulletin of Geosciences, 92(4): 13 pp.
Klug, C., Frey, L. Korn, D., Jattiot, R. and Rücklin, M. (2016). The oldest Gondwanan cephalopod mandibles (Hangenberg black shale, Late Devonian) and the mid-Palaeozoic rise of jaws. Palaeontology: 1-19 pp., doi: 10.1111/pala.12248
Frey, L., Maxwell, E., and Sánchez-Villagra, M. R. (2016): Intraspecifi c variation in fossil vertebrate populations: Fossil killifi shes (Actinopterygii: Cyprinodontiformes) from the Oligocene of Central Europe. Palaeontologia Electronica 19.2.14A: 1-27; palaeo-electronica.org/content/2016/1464-fossil-killifi shes-from-europe
Abstracts
Klug, C., Frey, L., Pohle, A., De Beats, K. & Korn, D. (2018b): Palaeozoic evolution of cephalopod mouthparts. 10th International Symposium on Cephalopods - Present and Past: p. 2, Fez.
Frey, L., Coates, M., Ginter, M., Klug, C. (2017): Skeletal Remains of Phoebodus politus Newberry 1889 (Chondrichthyes: Elasmobranchii) from a Famennian Konservatlagerstätte in the Eastern Anti-Atlas (Morocco) and its Ecology. 15th Annual Meeting of the European Association of Vertebrate Palaeontologists; p. 37, Munich.
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Curriculum Vitae
Frey, L., Coates, M., Ginter, M., Klug, C. (2017): Skeletal remains of Phoebodus politus Newberry 1889 (Chondrichthyes: Elasmobranchii) from a Famennian Konservatlagerstätte in the eastern Anti-Atlas (Morocco) and its ecology. 14th International Symposium on Early and Lower Vertebrates : p. 36, Checiny, Poland.
Klug, C., Frey, L., Pohle, A., Rücklin, M., (2017): Origin of the Konservatlagerstätten of the southern Maider (Morocco) and gnathostome preservation. 14th International Symposium on Early and Lower Vertebrates: p. 52, Checiny, Poland.
Frey, L., Coates, M., Ginter, M., Klug, C. (2016): The fi rst skeletal remains of Phoebodus politus Newberry 1889 (Chondrichthyes: Elasmobranchii) and its ecology. 14th Swiss Geoscience Meeting, 4. Palaeontology: p. 147, Geneva.
Klug, C., Frey, L., Korn, D., Jattiot, R., Rücklin, M. (2016): No fossil record? Yes fossil record! Konservat-Lagerstätten of the End-Devonian Hangenberg Black Shale in the eastern Anti-Atlas (Morocco). 14th Swiss Geoscience Meeting, 4. Palaeontology: p. 149, Geneva.
Klug, C., Frey, L., De Baets, K., and Korn, D. (2016): Paleozoic Marine macroecology. 1st Meeting of Early Stage Researchers in Palaeontology: p. 1, Alpuente (Valencia).
Frey, L., Rücklin, M., Kindlimann, R., and Klug, C. (2015): Alpha diversity and palaeoecology of a Late Devonian Fossillagerstätte from Morocco and its exceptionally preserved fi sh fauna. 13th Swiss Geoscience Meeting: p. 142, Basel,
Klug, C., Frey, L. and Rücklin, M. (2015): Preservation and taphonomy of Famennian Fossillagerstätten in the eastern Anti-Atlas of Morocco. 13th Swiss Geoscience Meeting: p. 144, Basel.
Frey, L., Rücklin, M., Kindlimann, R., and Klug, C. (2015): Alpha diversity and palaeoecology of a Late Devonian Fossillagerstätte from Morocco and its exceptionally preserved fi sh fauna. 13th International symposium on Early and Lower Vertebrates: p. 15, Melbourne
Klug, C., Frey, L. and Rücklin, M. (2015): Preservation and taphonomy of Famennian Fossillagerstätten in the eastern Anti-Atlas of Morocco. 13th international Symposium on Early and Lower Vertebrates: p. 21, Melbourne.