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First report of Hadrosia Cooper, 1983 in South America and its biostratigraphicaland palaeobiogeographical implications

Mena Schemm-Gregory a,b,*, Alexis Rojas-Briceño a, Pedro Patarroyo c, Carlos Jaramillo a

a Smithsonian Tropical Research Institute, P.O. Box 0843-03092, Panama City, Panamab Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Paläozoologie II, D-60325 Frankfurt am Main, GermanycDepartamento de Geociencias, Universidad Nacional de Colombia, Cr. 30 N. 45-03 or A. A. 14490, Bogotá, Colombia

a r t i c l e i n f o

Article history:Received 9 December 2010Accepted in revised form 9 November 2011Available online 17 November 2011

Keywords:TerebratulidaBrachiopodaRosablanca FormationLower CretaceousColombia

a b s t r a c t

A new terebratulid species, Hadrosia gracilis, from the Lower Cretaceous Rosablanca Formation in CentralColombia is described. The newmethod of three-dimensional reconstructions of the internal morphologyof this taxon results in the subjective synonymization of the Nerthebrochinae in favour of theSellithyridinae. The geographical distribution of species ofHadrosia in South America andWestern Europeis a further argument for a direct pathway between these two regions during Early Cretaceous time.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

In the eastern Andes of Colombia there are extensive outcrops ofa shallow marine, Lower Cretaceous sedimentary sequence consist-ing of more than 1000 m of carbonate and siliciclastic rocks. Up tonow, most of these outcrops have only been described in theframework of petroleum exploration (e.g., Cooper et al., 1995).However, detailed studies of the lithology and certain fossil groupswithmain focus on ammonites have been carried out during the pasthalf century (e.g., Bürgl, 1956; Etayo-Serna, 1964, 1968a, b, 1979;Patarroyo, 2000a, b, 2004; Bogdanova and Hoedemaeker, 2004;Sharikadze et al., 2004). Further fossil groups considered are bivalves(e.g., Dietrich,1938; Villamil,1996), crustaceans (e.g., Feldmannet al.,1999; Feldmann and Villamil, 2002; Vega et al., 2007, 2010),vertebrates (Langston et al.,1955;Hernandéz-CamachoandDePorta,1963; Páramo,1994,1997, 2000; Cadena and Gaffney, 2005; Ezcurra,2009), and plants (Huertas, 1967, 1970, 1976; Waveren et al., 2002;Correa et al., 2010). With exception of testudines and decapod crus-taceans (Cadena and Gaffney, 2005), however, a substantial

description of the majority of the pre-Barremian fossil content usingmodern palaeontological techniques is still lacking.

This paper is one of a series on the Cretaceous brachiopods fromColombia that we have carried out. Our data will help to establishthe history of Cretaceous brachiopod species, their evolutionwithinthe Andean region, and their relationship to southern Tethyanfaunas. The taxonomic information recorded as a result of thesestudies will elucidate the biogeographic history of the Andeanregion and help to interpret the structure and palaeoecology of itsmarine communities.

2. Geological settings and previous research

2.1. Geological settings

The basal calcareous rocks of the Cretaceous in Colombia arepresent in the Middle Magdalena Valley, including the Villa deLeyva area. They are represented mainly by the RosablancaFormation (Morales et al., 1958; Etayo-Serna,1968a, b; Rámon et al.,2001). The studied locality of the Rosablanca Formation is situatednear the “la Fábrica” cave south of the town of Santa Sofia, northernBoyacá Province, central Colombia (Fig. 1).

The Rosablanca Formation is described as a black micritic andalmost pure limestone sequence with a small percentage of clasticcomponents leading into grainstones and evaporites (Morales et al.,1958). In the study area the Rosablanca Formation is conformably

* Corresponding author. Present address: Centro de Geosciências e Departamentode Ciências da Terra da Universidade de Coimbra, Largo Marquês de Pombal3000-272, Portugal. Tel.: þ351 239 860 571; fax: þ351 239 860 501.

E-mail addresses: [email protected], [email protected](M. Schemm-Gregory), [email protected] (A. Rojas-Briceño), [email protected] (P. Patarroyo), [email protected] (C. Jaramillo).

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Cretaceous Research

journal homepage: www.elsevier .com/locate/CretRes

0195-6671/$ e see front matter � 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.cretres.2011.11.005

Cretaceous Research 34 (2012) 257e267


overlain by quartz siltstones of the Ritoque Formation (Etayo-Serna,1968a, b; Ballesteros and Nivia, 1985; Patarroyo, 1997b, 2009).Cardozo and Ramirez (1985) described in detail the lithostratigraphyof the Rosablanca Formation in the Ayal Creek at Santa Sofía. At thissection the formation consists of a lower sequence of 20 m ofmudstones, muddy sandstones, and grainstones followed by 103 mof micritic, biomicritic and calcareous mudstones, calcareous sand-stones, and dolomitized micrites. Specimens of Hadrosia occur inbeds of calcareous mudstones at the top of the Rosablanca Forma-tion; according to Cardozo and Ramirez (1985), between 10 and12 m below the onset of the overlying Ritoque Formation (Fig. 2).

The sedimentary environment of the Rosablanca Formation isinterpreted as a broad carbonate platform (Morales et al., 1958;Rámon et al., 2001). The dark to medium grey colour of the bedsbearing Hadrosia indicates lowered oxygen levels with a relativelyhigh supply of organic material (Pedersen and Calvert, 1990).Cardozo and Ramirez (1985) reported Chondrites and Thalassinoidesin the Upper Rosablanca Formation in Santa Sofía, which argues forlocal niches of more oxygenated conditions. They interpreted thesestrata as subtidal deposits adjacent to a tidal flat environment. In hisstudy on Cretaceous bivalves from Zapatoca, Santander Province,central Colombia, Dietrich (1938) described the brachiopod genusSellithyris as frequently found in “calizas margosas” or muddylimestones, but gave no further sedimentological information.

According to new ammonite data near Villa de Leyva (e.g.,Karakaschiceras Thieuloy, 1971, Raimondiceras Spath, 1924) strata ofthe Rosablanca Formation are assigned to the Valanginian Stage.However elsewhere, the uppermost part of the RosablancaFormation is referred to the Hauterivian (Haas, 1960; Guzman,1985) or HauterivianeBarremian (Patarroyo, 1997a) near Zapatocaor questionably lower Hauterivian (e.g., Acanthodiscus Uhlig, 1905)near Villa de Leyva, Boyacá Province.

The upper diachronous boundary of this lithostratigraphic unitis known because of a progressive transgressive event from the

central basin to the northwhere the Rosablanca Formation depositsare younger (e.g., Morales et al., 1958; Patarroyo, 1997b).

2.2. Studies on Colombian brachiopods

The oldest brachiopods of Colombia were reported byHarrington and Kay (1951) from the CambrianeOrdovician depositsin the Macarena Range without accurate stratigraphic location.Mojica et al. (1988) reported graptolites and some brachiopodsfrom the Middle Ordovician Hígado Formation in Tarqui, HuilaProvince. Bogotá (1982) and Thery et al. (1984) describedbrachiopods and indeterminate impressions that we, in accordancewith the authors, consider to be brachiopod remains in Ordoviciansediments of the Colombian Amazon Basin.

The most important work on Palaeozoic brachiopods isundoubtedly the monograph by Caster (1939) on brachiopods fromthe Devonian EmsianeEifelian Floresta Formation exposed near thevillage of Floresta, central Colombia (see also Barret, 1988).Recently, Janvier and Villarroel (2000) and Moreno (2004)described lingulid brachiopods from this unit.

Carboniferous brachiopods from Colombia, which are found instrata of the Garzon, Quetame, and Santander Massif (Trumpy, 1943;Olsson, 1956), have been studied by various authors: e.g., Gerth(1932), Kehrer (1933), Royo (1945), Stibane and Forero (1969), andAngiolini et al. (2003).Mojica et al. (1988) recordedbrachiopods fromthe same time interval, but without any specific determinations.

Fig. 1. Map of the study area with collecting locality indicated.

Fig. 2. Stratigraphic column for the Lower Cretaceous in Colombia.

M. Schemm-Gregory et al. / Cretaceous Research 34 (2012) 257e267258


Mesozoic brachiopods from Colombia have been poorly studiedhitherto. Several authors (e.g., Geyer, 1973; Stibane, 1976; Sandy,1990, 1991a, b) showed that some marine, almost unfossiliferoussediments of Palaeozoic to Jurassic age were misplaced for manyyears in the “red beds of Colombia”. Cretaceous brachiopodsdescribed so far include the terebratulids Arenaciarcula beaumonti(d’Archiac, 1847) and Gemmarcula cf. menardi (Lamarck, 1819),stored in the d’Orbigny Collection in Paris, as well as Musculina aff.sanctaecrucis (Catzigras, 1948) (Guzman, 1985). Representatives ofSellithyris sella (Sowerby, 1823) from Zapatoca were reported byd’Orbigny (1851), Karsten (1858, 1886), and Dietrich (1938) underthe names Terebratula sella Sowerby, 1823 and Terebratula haueriKlippstein, 1844. Themost recent studies on brachiopods have beencarried out by Rojas-Briceño and Patarroyo (2009, 2010); however,the data published so far are mostly preliminary.

Cenozoic brachiopods from Colombia are basically unknown.Preliminary reports consist of Recent terebratulids from theCaribbean Coast (Rojas-Briceño et al., 2009). Monospecific clustersof the discinid brachiopod Discradisca Stenzel, 1964 found in theMalaga Bay on the Pacific coast are currently under investigation(Rojas-Briceño, unpublished data).

3. Stratigraphy and palaeobiogeography of Hadrosia

3.1. Biostratigraphic value

Mesozoic brachiopods are characterized by strong homoplasyand a decline in abundance and diversity towards the Cenozoic.Their high intraspecific and intrageneric variability does not easetheir use as biostratigraphical and palaeobiogeographic tools.However, previous studies have shown that Cretaceous brachiopodsare important for biostratigraphy and palaeobiogeography duringthis time interval (e.g., Grãdinaru et al., 2006; Lobatscheva andSmirnova, 2006; Middlemiss, 1981, 1984a, b; Laz�ar et al., 2010).The preparation of serial sections is an essential method foranalyzing the internal shell structures of often externally verysimilar specimens of Mesozoic brachiopod taxa. New digitalreconstruction techniques allow detailed taxonomic identificationin spite of the strong homoplasy (see ‘Material and methods’).

Brachiopod genera of the family Sellithyrididae are geographi-cally widely distributed and very abundant in Lower Cretaceousstrata. Even though the majority of these taxa are externally verysimilar they represent good index fossils for this time span. Thebrachiopod genus Hadrosia is so far only reported from theValanginian; as a result the occurrence of Hadrosia within theRosablanca Formation confirms their Valanginian age. However,with the proposed Valanginian to ?early Hauterivian age of theRosablanca Formation, the time span of this genus might extendalso into the Hauterivian, but only when the precise biostratigraphyof the Rosablanca Formation in different places is known will it bepossible to prove that the range of the genus in Colombia isrestricted only to the Valanginian as has been indicated hitherto.

Dietrich (1938) partly studiedmaterial of the fauna fromZapatoca,200 km north of Santa Sofía, which contains a well-preservedassemblage dominated by Sellithyris sp., but the exact stratigraphicalposition of his material is uncertain and internal descriptions are notavailable. Sandy (1990, p. 420, fig. 5.3aed) figured a specimen ofDietrich’smaterialwhich he assigned in a laterwork to the SaynocerasHorizon (cf. Sandy, 1991b, p. 143). There are extensive unexploredoutcrops of shallow marine, Lower Cretaceous sediments in theeastern Andes of Colombia including Boyacá and Santander provincesand other similar sediments in Guajira Province.We assume that theyare likely to containing a rich record of brachiopods includingHadrosia. It is necessary to state that even though no Sellithyris occursin our material, it may be present in other localities in Colombia.

Therefore, we suggest thatHadrosia gracilis sp. nov. is a possible indexfossil for the upper part of the Valanginian Stage in this region.

3.2. Palaeobiogeographical value

Owing to the lack of modern palaeontological studies,a consensus biogeographical interpretation of the Early Cretaceousof Colombia is still lacking (Hoedemaeker, 2004).

On a global scale, taxa of the Sellithyrididae have been used tointerpret the palaeobiogeography and faunal relationships amongTethyan faunas during the Early Cretaceous (e.g., Sandy et al., 1995;Grãdinaru et al., 2006). One example is the cosmopolitan distribu-tion of the low latitude Tethyan genus Sellithyriswhich indicates thepresence of faunal pathways in coincidence with the opening of theNorth Atlantic Ocean (Sandy, 1990, 1991a, b, 1997; Gaspard, 2005).Manceñido (2002) also discussed faunal exchange and the rela-tionship between brachiopod faunas in northern SouthAmerica andWestern Europe as a result of the opening of the South AtlanticOcean; however, this fauna pathway occurred somewhat later. Thefaunal relationship between South America and North America andwith Europe, furthermore, is recognizable in coral and molluscanfaunas (Von Der Osten, 1957). The occurrence of Hadrosia in Franceand Colombia confirms the hypothesis of a faunal migration waythrough the low latitude Tethys (Fig. 3), whichwasfirst discussed byHaas (1960). He described the similarity of Lower Cretaceousammonites found in a locality about 100 km southeast of the locality“Santa Sofía” in our study area to other Tethyan forms. On otherhand, Etayo-Serna et al. (1976) argued that at the specific level theHauterivian ammonites from Colombia are closely related to thoseof Peru and at the generic level to Mexican forms.

4. Material and methods

The material is preserved as articulated, but sometimes partlyabraded, shells. To study the internal morphology, the preparation ofserial sectionswas theonlypossiblemethod.Computer tomographicalscans have turned out to be useless because the composition of shellmaterial and sediment matrix of these specimens does not allowsufficient differences for good images. However, the modern

Fig. 3. Palaeogeographical map for the Early Cretaceous showing the occurrences oftaxa of Hadrosia and their migration way through the Tethys. (Map from Ron Blakey,NAU Geology; http://jan.ucc.edu).

M. Schemm-Gregory et al. / Cretaceous Research 34 (2012) 257e267 259


laboratory techniques that we use to analyze the peels allow detailed3D reconstructions of the internal features of the articulated speci-mens (e.g., Schemm-Gregory et al., 2008; Feldman et al., 2010;Schemm-Gregory, 2010). As a result, direct comparison of theinternal morphology of our specimens enables us to elucidate onto-genetical and phylogenetical relationships and, in a second step, tocontribute to new implications for palaeobiogeographical interpreta-tion. Several hundred serial sections of representative specimenswerepreparedusingaWOKO50Pgrindingmachinewith slice-spacingof 50and 100 mm. Acetate peels were used to record the morphologicalinformation from each slice; these were subsequently digitized usinga digital camera (Canon 300 D). Three-dimensional reconstructionmethods are those of Sutton et al. (2001, 2005), which were imple-mentedusing the customSPIERS software suite for registration, virtualpreparation, and interactive visualization. The digitized acetate peelswere subsequentlymanuallyalignedwithSPIERSalignand, in a secondstep, edited using different masks in SPIERSedit. The 3D images arecopied out of SPIERSview. SEM pictures were taken of uncoatedspecimens in a lowpressure vacuumat25kbar and15kVand spot sizeof 60 with a JSM-6490LV machine. Drawings of the peels were donewith help of a camera lucida. Measurements were taken with digitalcallipers and rounded to 0.1 mm or using the free ImageJ 1.43u soft-ware. Specimens were coated with ammonium chloride prior tophotography. The systematics follows the revised “Treatise on Inver-tebrate Paleontology” (Lee and Smirnova, 2006).

Institutional abbreviations. UN-DG-BR,DepartamentodeGeociencias,Universidad Nacional de Colombia, Bogotá, Colombia; USNM,Smithsonian Institution/National Museum of Natural History,Washington DC, USA; YPM, Peabody Museum of Natural History,Yale University, New Haven, CT, USA.

5. Systematic palaeontology

Phylum Brachiopoda Duméril, 1806Subphylum Rhynchonelliformea Williams et al., 1996Class Rhynchonellata Williams et al., 1996Order Terebratulida Waagen, 1883Suborder Terebratulidina Waagen, 1883Superfamily Terebratuloidea Gray, 1840Family Sellithyrididae Muir-Wood, 1965Subfamily Sellithyridinae Muir-Wood, 1965

Remarks. In this study we consider the genera of the subfamilyNerthebrochinae Cooper, 1983 to be members of the SellithyridinaeMuir-Wood, 1965, because in our opinion the morphologicaldifferences between the genera given in their diagnosis are notsufficient for justify the erection of a subfamily (Cooper, 1983, p. 38,Table 1); rather they represent differences at the genus level.Furthermore, the genus assignments to these two subfamilies,Sellithyridinae and Nerthebrochinae, are interpreted differently inCooper (1983, p. 38) and the revised “Treatise of InvertebratePaleontology” (Lee and Smirnova, 2006, pp. 2062e2066). Subse-quently, we propose the synonymization of the Nerthebrochinae.Additional studies are strongly recommended to prove our argu-ment; however, the revision of the family Sellithyrididae is farbeyond the scope of this work.

Genus Hadrosia Cooper, 1983

Type species. Hadrosia convexa Cooper, 1983, pp. 195, 196, pl. 17, figs.36e41, pl. 67, figs. 8, 9.

Table 1Morphological comparison of Hadrosia and Sellithyris.

Hadrosia gracilis sp. nov. Hadrosia convexa Cooper, 1983 Sellithyris Middlemiss, 1959

size small to medium medium to large small to mediumoutline elongate elliptical elongate elliptical pentagonal, almost as wide as longcurvature equi- to gently

ventribiconvexequi- to gentlyventribiconvex

usually ventribiconvex, rarelyequibiconvex

anterior margin strongly sulciplicate narrowly sulciplicate strongly sulciplicateforamen large, permesothyridid large, permesothyridid large, meso- to permesothyrididsymphytium hardly concealed mostly concealed fully visiblemedian sulcus short, deep short, deep highly variablemedian myophragm present unknown presentlateral ridges present unknown absent/presentloop angle 29e30� 95e100� 40e45�

loop length and width 1/3 of length and widthof dorsal valve

1/3 of length and widthof dorsal valve

slightly more than 1/3 of length andwidth of dorsal valve

cardinal process small half ellipse small half ellipse half ellipse, wide, thin, indented mediallysocket ridges thin, erect, gently curved thin, erect, clearly arched thin, erect, gently curvedsockets broad narrow broadfulcral plates small, without lateral

extensionsunknown small, without lateral extensions

outer hinge plates wide, triangular, short,extend to the base ofthe crural process

fairly wide, triangular,short, extend to the baseof the crural process

fairly wide, end in a point just below(dorsal) of the crural process

crural bases thin, forming a high ridge broad, forming a high ridge elevatedcrural processes anterior to midloop,

sharply angular, directedventeromedially

anterior to midloop, stoutlyangular, directed antermedially

anterior to midloop, acutely pointed,moderately long,

descending lamellae short, laterally curved,angle 30�

short, laterally curved, wide short, outwardly curved, narrow

transverse band broad, strongly arched,steep lateral sloops,almost horizontal

stout, broad, strongly arched,steep lateral slopes, 25�

from horizontal

narrow, strongly arched, protuberant,almost horizontal

median crest short, broadly rounded short, angular to rounded 1/3 of transverse band, narrow roundedterminal points extended, short and rounded extended, short and rounded not extended, roundedGeographic distribution Colombia Basses Alpes, France Great Britain, Central Europe, ?cosmopolitanStratigraphic distribution Valanginian, ?Hauterivian Valanginian AptianeTuronian



Fig. 4. AeAF, Hadrosia gracilis sp. nov. AeI, UN-DG-BR 9449. A, ventral, B, dorsal, C, lateral, D, anterior and E, posterior views of articulated shell. F, oblique lateral view of loop.G, upper view of ventral internal shell. H, upper and I, oblique lateral views of dorsal internal shell. J-T, UN-DG-BR 9453. J, dorsal, K, ventral, L, anterior, M, lateral and N, posteriorviews of articulated shell. O, P, upper views of O, internal dorsal and P, ventral shell. Q, oblique posterior view of dorsal internal shell. R, oblique lateral view of loop. S, T, apicalregion of S, dorsal and T, ventral shell. Scale bars represent 2 mm in F, R, 5 mm in S, T. UeZ, UN-DG-BR 9455, holotype, in U, ventral, V, dorsal, W, anterior, X, Y, lateral andZ, posterior views of articulated shell. AAeAF, UN-DG-BR 9465, articulated shell in AA, AC, lateral, AB, anterior, AD, ventral, AE, posterior and AF, dorsal views. AGeAI, Hadrosiaconvexa Cooper, 1983. AG, AH, USNM 550930a, holotype in U, ventral and V, dorsal views. AI, USNM 550930e. Ventral view of loop on dorsal interior. All figures are �1.5 unlessotherwise indicated.



Emended diagnosis. Medium-sized sulciplicate shells with a shallowumbonal chamber and an anterior rounded loop with a stout, broadtransverse band. (Modified after Cooper, 1983, p. 195).

Stratigraphic and geographic distribution. Valanginian, ?Hauterivian(Lower Cretaceous); France and Colombia.

Species included. Hadrosia convexa Cooper, 1983; Hadrosia gracilissp. nov.

Remarks. Externally Hadrosia is most closely similar to SellithyrisMiddlemiss, 1959 within the Sellithyridinae Muir-Wood, 1965, butshows stronger convex valves and a more incurved beak. The loop inHadrosia differs from Sellithyris in being at a narrower angle, and inhaving a more anterior crural process, a more strongly transverseband that extends much closer under the crural process, and morepronounced terminal points from the loop. A morphological

comparison between Sellithyris and taxa of Hadrosia is given inTable 1.

Hadrosia gracilis sp. nov.Figs. 4e7, Appendix

1985 Terebratulla sella Sowerby: Guzman, p. XII-5.v 2009 Sellithyris sella (Sowerby): Rojas-Briceño and Patarrayo.v 2010 Sellithyris cf. sella (Sowerby): Rojas-Briceño and Patarrayo,

p. 91.

Derivation of name. Latin, gracilis, thin, with reference to the elon-gate shell form.

Holotype. Articulated specimen illustrated in this work (Fig. 4UeZ)and housed in the Departamento de Geociencias, UniversidadNacionaldeColombia, Bogotá, Colombia, under the inventorynumberUN-DG-BR9455. Length23.3mm,width19.2mm, and thickness12.5.

Fig. 5. SEM micrographs showing the calcitic fibres of the secondary shell layer (AeE) and the punctae of the primary shell layer (F) of Hadrosia gracilis. A, B, UN-DG-BR 9449. CeF,UN-DG-BR 9453.



Type locality. Near “la Fábrica” cave and Las Juntas south of the townof Santa Sofía, Boyacá Province, central Colombia.

Stratigraphic horizon. Upper Rosablanca Formation, Valanginian,?Hauterivian, Lower Cretaceous.

Stratigraphic and geographic distribution. As for genus.

Diagnosis. Elongated Hadrosia with a well-developed sulcus,a partly concealed symphytium, thin crural bases, a broadlyrounded median crest, and a crural process directed perpendicularto the commissural plane.

Fig. 6. Serial sections through Hadrosia gracilis. AeAC, UN-DG-BR 9453, all figures �3.0; sectioning perpendicular to commissural plane, sectioning distance in mm from posterior: bs,brachiopod shell; cb, crural base; cp, cardinal process; crpr, crural process; daf, dorsal adductorfield; dl, descending lamella; ds, dental socket; dv, dorsal valve; fp, fulcral plate; im, internalmould; m, myophragm; ohp, outer hinge plate; pf, pedicle foramen; pf, pedicle foramen; r, ridge; sr, socket ridge; t, tooth; tb, transverse band; uc, umbonal chamber; vv, ventral valve.



Material. Eight articulated shells: UN-DG-BR 9449, 9453 (used forserial sections), 9455 (holotype), 9460 (incomplete), 9465, 9468,9471,1001; three partly abraded external ventral valves: UN-DG-BR9476, 1002, 1003. The material with measurements is given inAppendix A.

Description. Shell: specimens small to medium-size, outline sub-elliptical elongate in a longitudinal direction with maximumwidthat midlength or shortly anterior to it. Shells equibiconvex toventribiconvex in longitudinal section with smooth surface.Anterior margin narrow sulciplicate at adult stage; in juvenilestages rectimarginate. Median sulcus short, begins anterior of

mid-length of shell. Fold within sulcus narrow, weak to strong, andclearly conspicuous. Shells swollen in umbonal regions ofboth valves, ventral beak erect. Pedicle foramen large and per-mesothyrid. Pedicle collar clearly developed. Symphytium con-cealed by dorsal beak. Beak ridges not visible.

SEM images obtained from non-coated specimens in a lowvacuum mode at 15 kV show the primary layer (Fig. 5C) and thecalcitic fibres of the secondary layer (Fig. 5). At the dorsal anteriormargin well-preserved punctae across the calcitic fibres showa density of 197 punctae/mm2. (Fig. 5F).

Interior of ventral valve: internal shell of ventral valve unspec-tacular. Ventral sulcus and median fold clearly impressed. Small

Fig. 7. Serial sections through Hadrosia gracilis. AeQ, UN-DG-BR 9449, all figures �3.0; sectioning perpendicular to commissural plane, sectioning distance in mm from posteriorend: bs, brachiopod shell; cb, crural base; crpr, crural process; dl, descending lamella; ds, dental socket; dv, dorsal valve; fp, fulcral plate; im, internal mould; ohp, outer hinge plate;sr, socket ridge; t, tooth; tb, transverse band; tp, terminal point; vv, ventral valve.



and cyrtomatodont teeth are oriented at an angle of ca. 45� to eachother (Figs. 4T, 6R).

Interior of dorsal valve: umbonal chamber shallow. Cardinalprocess small, outline inconspicuous in our material (Fig. 6K).Dorsal diductor field comb-like striated (Fig. 6P). Socket ridges thinand gently curved over the broad dental sockets at the anterior end.Fulcral plates small, oriented parallel to commissural plane, andwithout lateral extensions. Outer hinge plates thick, triangular, andextending as a ridge in an interior direction towards the cruralprocess of the deltiform and short loop, which is less than one thirdof shell length. On their inside margin the thin crural bases forma high ridge almost perpendicular to the commissural plane andlead into the crural process. Crural processes sharp, pointing ina ventromedian direction, and situated at or shortly anterior ofmid-loop reaching into the ventral valve (Figs. 6Y, 7I, J). Descendinglamellae short, gently curved in a lateral direction and situated inan angle of 30� to each other. Transverse band broad, arched, andwith steep lateral slopes that are almost perpendicular tocommissural plane (Figs. 4F, I, 7L, M). Terminal points short andanterior rounded (Fig. 4F, R; Appendix B). Dorsal adductor fielddivided by a low, faint medium myophragm and one lateral ridgeon either side of it (Fig. 6R, S). Measurements of specimens studiedand of the loops are given in the appendices.

Discussion. The differences between the morphological features ofHadrosia gracilis sp. nov. and the type species, Hadrosia convexaCooper, 1983, justify the erection of a new species. Hadrosia gracilisdiffers fromH. convexa in smaller shells, a more conspicuous sulcus,a somewhat concealed symphytium, less curved socket ridges,broader sockets, wider outer hinge plates, a broadly roundedmedian crest, and a crural process that is oriented in a ventraldirection. The type species is characterized by a mostly concealedsymphytium, an angular to rounded median crest, and a cruralprocess that is oriented in an anteromedial direction. Furthermore,the descending lamellae are closer to each other in the new speciesthan in H. convexa. The transverse band in H. gracilis is almosthorizontal, whereas it is inclined about 25� from horizontal inH. convexa. According to Pérez-Huerta et al. (2009), the density andmorphology of punctae is species-specific. At this stage of researchwe could not study the shell material of H. convexa. Therefore,a further test for checking whether it is conspecific (or not) maybecome available in the future when the shell fabric of the typespecies of Hadrosia is studied in detail by SEM. A brachiopod that isvery similar externally to H. gracilis from the “Neocomian” ofBerklingen, Germany, is stored at the Peabody Museum of NaturalHistory, Yale University (YPB IP 227853). Without serial sections itis impossible to say if it is a representative of Hadrosia. If it is, thisspecimen would support our argument for the migration pathwayof Hadrosia through the low latitude Tethys.

A slightly older terebratulid “Terebratula” kanei Imlay, 1940 hasbeen reported from the Valanginian Barril Viejo shale of northernMexico. It differs from Hadrosia externally in having a lessconspicuous sulcus and a wider shell (Imlay, 1940). The internalstructures are unknown; as a result, a generic assignment accord-ing to a modern palaeontological approach is not yet possible. Thisspecimen might be a representative of Hadrosia or a related form,depending on its internal morphology.

6. Conclusions

New digital three-dimensional reconstruction techniquesconfirm the identification and presence of Hadrosia in SouthAmerica. Its relationship to the Western European species supportsthe argument for a faunal pathway between northern South

America and Western Europe in coincidence with the opening ofthe South Atlantic Ocean during the Early Cretaceous. Furtherstudies of that brachiopod bioevent including Hadrosia, Sellithyris,and hitherto unidentified taxa in the Lower Cretaceous strata of theAndean region will provide and excellent opportunity for evalu-ating the partially contradictory ideas about the climatic conditionsduring ValanginianeHauterivian times (Weissert and Lini, 1991,1998; Lini et al., 1992; Price, 1999; Aguirre-Urreta et al., 2008). Inaddition, an accurate taxonomic determination of brachiopodassemblages supported by high-resolution 3D reconstructions willbe useful to test the provinciality of low latitude Tethyanbrachiopod faunas, which has been suggested by Middlemiss(1984b).

Acknowledgements

The research of MS-G in Panamá was partly financed by theSmithsonian Tropical Research Institute. The visit of AR-B to thePeabody Museum, Yale University was paid by a Charles Schuchertand Carl O. DunbarGrant. Both authors acknowledge the following atthe Senckenberg Forschungsinstitut und Naturmuseum, Frankfurtam Main, Germany: Bernhard Stribrny for providing access to thelaboratory; Tina Emmel and Michael Ricker for technical help;Claudia Franz for the SEM images. MS-G is grateful to EberhardSchindler of the same institute for providing herwithworking space.Michael Brett-Surman (USNM) took the photographs of the Cooper’smaterial. PP thanks the company of geology students of theUniversidad Nacional de Colombia, during the field work in SantaSofía. The manuscript has greatly benefited from the comments byRobert B. Blodgett (Anchorage, USA) and Miguel O. Manceñido(Museo Ciencias Naturales de La Plata, Argentina).

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Appendix

A, measurements of Hadrosia gracilis sp. nov.

Inventory no. Width/mm Length/mm Thickness/mm

UN-DG-BR 9449 14.7 22.6 10.3UN-DG-BR 9453 15.5 20.3 9.7UN-DG-BR 9455holotype

19.2 23.3 12.5

UN-DG-BR 9460 17.2 NA 11.6UN-DG-BR 9465 8.7 10.0 6.6UN-DG-BR 9468 NA NA NaUN-DG-BR 9471 NA NA NAUN-DG-BR 9476 15.3 18,3 NAUN-DG-BR 9463 14.2 16.3 8UN-DG-BR 9470 13.0 NA NAUN-DG-BR 9474 15.2 19.4 NA

B, parts of the loop used for measurements. Measurements are in accordance tothose of Cooper (1983, p.14, fig. 2): A, loop angle; a, distance from cardinal process totip of crural process (a focal point in the loop); b, distance from tip of crural processto end of terminal point; c, measure of outer hinge plate; d, measure of crus, fromend of outer hinge plate to tip of crural process; e, distance from crural process tobridge (or apex) of transverse band; f, length of terminal points; g, width of hinge; h,measure of transverse band at its apex; LI (a þ b), length of loop; Wl, width of loop.

UN-DG-BR 9449 UN-DG-BR 9453

Ll 6.0 mm ?Wl 3.9 mm ?a 3.3 mm 3.4 mmb 2.6 mm ?c 2.1 mm 2.0 mmd 3.8 mm 1.4 mme 1.5 mm ?f 1.1 mm ?g 3.8 mm 4.3 mmh 0.4 mm ?A 29.8� 29.5�


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