Trilobites - PaleoArchivepaleoarchive.com/literature/Brutonetal1979-VattenfalletTrilobites.pdf ·...
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116 Trilobites DAVID L. BRUTON, VALDAR JAANUSSON, ROBERT M. OWENS, DEREK J. SIVETER, and RONALD TRIPP The last comprehensive review of the trilobites from Gotland was that by Lindström (1885). Since then a few additional species have been described but only some small groups have been thoroughly revised (Odontopleuridae, Bru- ton 1967; Encrinurus punctatus group, Tripp 1962). Proctids and calymenids are currently being described monographically by R.M. Owens and D.J. Siveter, respectively, but most of the remainder of the fauna is badly in need of revision. The total number of specimens of trilobites in the material from Vatteallet is 846, distributed among the following families: Odontopleuridae ( 14 speci- mens), Illaenidae (39) , Cheiruridae (8), Proetidae (265), Aulacopleuridae ( l) , Phacopidae (225), Dalmanitidae ( 1) , Calymenidae ( 120), Encrinuridae ( 150), and Lichidae (23). The total number of individuals may have been somewhat smaller than the number of specimens recorded, since in any one bed several specimens might have belonged to a single disarticulated specimen, but it is impossible to determine this. Moreover, occasionall y, small specimens may have been moult stages of individuals represented in the same bed by large specimens. In this paper Bruton is responsible for odontopleurids, Jaanusson for il- laenids and cheirurids, Owens for proetids, aulacopleurids, phacopids, and dalmanitids, Siveter for calymenids, and Tripp for encrinurids and lichids. For ranges in the section see Fig. 3 1 . Annotated faun al list Odontopleuridae Dudleyaspis ? sp. indet. , Leonaspis s p. indet. (13. 1 m), Leonaspis angelini (Prantl and Pfibyl) , Acidaspis pectinata Angelin, Anacaenaspis sp. (cf. A. aff. gotlandensis, Bruton 1967, PI. 35:9 only). Illaenidae Buastus holi Lindström, Buastus n. sp. a, Buastus sp. b (8-10 m). Buastus is not uncommon in the Högint beds but most specimens are either fragments, intemal moulds, or juvenile pygidia (see Buastus sp. indet. in the log, Fig. 31).
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Trilobites
DAVI D L. B R U T O N , VAL DAR JAAN USS O N , ROBERT M. OWENS,
DEREK J. SIVETER, and RONALD TRIPP
The last comprehensive review of the trilobites from Gotland was that by Lindström ( 1 885) . Since then a few additional species have been described but only some small groups have been thoroughly revised ( Odontopleuridae , Bruton 1967 ; Encrinurus punctatus group , Tripp 1 962) . Proctids and calymenids are currently being described monographically by R . M . Owens and D .J . Siveter, respectively , bu t most of the remainder of the fauna i s badly in need of revision.
The total number of specimens of trilobites in the material from Vattenfallet is 846 , distributed among the following families : Odontopleuridae ( 14 specimens) , Illaenidae (39) , Cheiruridae (8) , Proetidae (265) , Aulacopleuridae (l) , Phacopidae (225) , Dalmanitidae ( 1) , Calymenidae ( 120) , Encrinuridae ( 150) , and Lichidae (23) . The total number of individuals may have been somewhat smaller than the number of specimens recorded , since in any one bed several specimens might have belonged to a single disarticulated specimen, but it is impossible to determine this . Moreover , occasionall y, small specimens ma y have been moult stages of individuals represented in the same bed by large specimens .
In this paper Bruton is responsible for odontopleurids , Jaanusson for illaenids and cheirurids , Owens for proetids , aulacopleurids , phacopids , and dalmanitids , Siveter for calymenids , and Tripp for encrinurids and lichids .
For ranges in the section see Fig . 3 1 .
Annotated faun al list
Odontopleuridae Dudleyaspis ? sp . indet . , Leonaspis s p. indet. ( 1 3 . 1 m) , Leonaspis angelini
(Prantl and Pfibyl) , Acidaspis pectinata Angelin , Anacaenaspis sp . (cf. A . aff. gotlandensis , Bruton 1 967 , PI . 35 :9 only) .
Illaenidae Burnastus holrni Lindström , Burnastus n. sp . a, Burnastus sp. b (8-10 m) . Burnastus is not uncommon in the Högklint beds but most specimens are either fragments , intemal moulds , or juvenile pygidia (see Burnastus sp . indet . in the log , Fig . 3 1) .
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Cheiruridae Deiphon sp . (only very small cranidia) , Youngia sp .
Proetidae Proetus (Proetus) concinnus Dalman , P. (Lacunoporaspis) cf. conjossus
Owens , P. (L . ) n . sp . (aff. signatus Lindström) , Warburge/la ( Warburgella)
n.sp. a , W. ( W.) baltica Alberti , W. ( W.) cf. stokesii ( Murchison) , Warburge/la
sp . indet . (9 . 20-10 .0 m, 1 3 . 55 m, 1 3 .85 m) . The specimens ofProetus (Proetus)
from the Upper Visby Mari (given in the log , Fig . 3 1 , as P. (P.) s p. indet . ) ma y indude P. (P.) concinnus but the material is too fragmentary to resolve the problem.
Aulacopleuridae Harpideila sp. a . This species , represented by a single cranidium, appears to be specifically distinct from the common Mulde Mari species H. elegantula
(Loven) .
Phacopidae Acernaspis sp . a, A . sp . b .
There are two dosely related , and apparently new phacopid species represented , both referable to A cernaspis . Detailed comparison with other species is not possible here , since with a few exceptions , most are badly in need of redescription.
Dalmanitidae Acastocephala cf. maerops (Salter) ( Högklint c, exact level unknown) .
Calymenidae Calymene frontosa Lindström, C. blumenbachii Brongniart n. subsp . a .
Encrinuridae Encrinurus laevis ( Angelin) , E. punctatus (Wahlenberg) , E. sp . a .
In E . punctatus , variation i n the arrangement of tuberdes o n the glabella and anterior border of the cranidium have been recorded on specimens from the Högklint Limestone , Slite Mari and Jaani Mari (Tripp 1 962 : 467 , Table 1 ) . Comparable statistics for lithostratigraphical subdivisions a , b , and c of the Högklint Beds , Vattenfallet, are as shown on Table 3 . A rare variant is a cranidium from 1 8 .45 m , in which there is a pair of small l - l tuberdes in place of 1 - 0 . Hypostomes are similar to the specimen from the Slite Beds figured by Tripp ( 1 962 , PI . 67 , tigs . 8a, b) . In most pygidia the mucro appears to have been large , but is broken off. There is one non-mucronate pygidium , from
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19 .45- 19 .50 m, comparable in most respects with the lectotype (Tripp & Whittard 1956, PI . 3) .
On e free cheek , from 24 .80-25 .20 m. , here referred to E. s p . a , is distinguished from species of the E. punctatus species group in the coarse pitting of the field of the cheek .
Lichidae Arctinurus ornatus (Angelin) , A . palifer (Lindström) , an euarginid hypostome ( 10 .0-10 .8 m; not Iikely to betong to Trochurus as Iisted by Hedström 19 10) .
Str atigraphical remarks
Details of the vertical range of various trilobite species in the stratigraphical interval under consideration are still poorly known on Gotland , in part because the precision of stratigraphical and geographical data on labels accompanying extensive old collections is insufficient for modern need s . In the Vattenfallet material the replacement of Enerinnrus laevis by E. punctatus at the base of Högklint a is particulariy noteworthy ( Fig . 3 1) . The latter species has repeatedly been recorded also from the Upper Visby Mari but its occurrence there requires confirmation .
lt is interesting to note that the taxonornie di versity of trilobite species (see also Fig . 76) is much higher in Högklint b (estimated number of species in the material 14) and Högklint c ( 1 3) than in the Upper Visby Mari (9) . Högklint a
has yielded about as many trilobite species (7) as the Upper Visby Mari .
TABLE 3 . Comparison of specimens of Encrinurus punctatus from the l ithostratigraphical subdivisions a. b. and c of the Högklint Limestone . Vattenfal let .
M etre s above sea-leve!
1 0 . 0- 1 3 . 0- 2 4 . 0 1 3 . 0 2 4 . 0 29 .6
N umber of speci mens: Cranidium Cranidia studied 1 2 5 With tuberc l e iii-O 1 2 4 With an y of the 4 iii-2 : 9 4 With 8 tuberdes on anterior border 7 l With 9 tuberdes on anterior border With l O tuberdes on anterior border l Uncertain 4 4
Pygidium Pygidia studied 2 1 5 1 4 With first tuberde on first ring 3 l With first tuberde on seeond ring 2 I l 1 2 With first tuberde on third ring l l Specimens showing correlation of position of axial and
pleural tuberdes 6 4
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REFEREN CES
BRUTON , D .L . , 1%7 : Silurian odontopleurid trilobites from Sweden , Estonia, and Latvia. -Palaeontology 10: 2 1 4-244.
HE DSTRÖ M , H . , 19 10 : The stratigraphy of the Silurian strata of the Visby district . - Geol . Fören. Stockholm Förh. 32 : 1455-1484.
LIN DSTRÖ M , G . , 1885 : Förteckning på Gotlands Siluriska Crustaceer. - Öfversigt K. Sven . Vet.-Akad . Förhand! . 1885. 6 : 37-100.
TRIPP, R. P. , 1962: The Silurian trilobite Encrinurus punctatus (Wahlenberg) and allied species . - Palaeontology 5 :460-477.
- & W HITT A R D , W . F . , 1956: Proposed u se of the plenary powers (a) to designate type species in harmony with accustomed usage for the genera " Encrinurus" Emmrich, 1844 and " Odontochile" Hawle and Corda, 1847 , and (b) to validate the specific name "punctatus" Wahlenberg, 1 82 1 , as published in the combination " Entomostracites punctatus" (Ciass Trilobita) . - Bull . Zool . Nomencl . 12 :259-263 .
