A new species of <i>Cyclotosaurus</i> (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus
A nearly complete dermal skull roof of a capitosaur stereospondyl with closed otic fenestrae from the middle Carnian Stuttgart Formation (Late Triassic) of Bielefeld-Sieker (NW Germany) is described. The specimen is assigned to the genus <i>Cyclotosaurus</i> based on the limited contr...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Pensoft Publishers
2016-03-01
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| Series: | Fossil Record |
| Online Access: | https://www.foss-rec.net/19/83/2016/fr-19-83-2016.pdf |
| Summary: | A nearly complete dermal skull roof of a capitosaur stereospondyl with
closed otic fenestrae from the middle Carnian Stuttgart Formation (Late
Triassic) of Bielefeld-Sieker (NW Germany) is described. The specimen is
assigned to the genus <i>Cyclotosaurus</i> based on the limited contribution of the frontal to
the orbital margin via narrow lateral processes. A new species,
<i>Cyclotosaurus buechneri</i> sp. nov., is erected based upon the following unique combination of
characters: (1) the interorbital distance is short so that the orbitae are
medially placed (shared with <i>C. robustus</i>); (2) the region lateral to the orbitae is
only slightly broader than the orbitae (shared with <i>C. posthumus</i>, <i>C. ebrachensis</i>, <i>C. intermedius</i>, and <i>C. mordax</i>); (3) the
postorbital region is slender (shared with <i>C. ebrachensis</i>); (4) the preorbital projection
of the jugal is shorter than half the length of the snout (shared with <i>C. mordax</i>, <i>C. ebrachensis</i>,
<i>C. intermedius</i>, <i>C. posthumus</i>, and <i>C. hemprichi</i>). A phylogenetic analysis of seven <i>Cyclotosaurus species</i>, including <i>C. buechneri</i>, and eight further
capitosaur taxa with the Rhinesuchidae as an outgroup finds a monophyletic
<i>Cyclotosaurus</i>. In accordance with its stratigraphic occurrence, <i>C. buechneri</i> nests at its base but is
more derived than <i>C. robustus</i>. Among the more derived <i>Cyclotosaurus</i> species, <i>C. ebrachensis</i> and <i>C. intermedius</i>, as well as <i>C. posthumus</i> and
<i>C. hemprichi</i>, form sister groups, respectively. However, the phylogenetic position of <i>C. mordax</i>
with respect to both groups remains unresolved. In the phylogenetic analysis
presented here, <i>Cyclotosaurus</i> is the sister group of the Heylerosaurinae
(<i>Eocyclotosaurus</i> + <i>Quasicyclotosaurus</i>). <i>Cyclotosaurus buechneri</i> represents the only unequivocal evidence of <i>Cyclotosaurus</i> (and of a cyclotosaur
in general) in northern Germany. |
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| ISSN: | 2193-0066 2193-0074 |