Cranial anatomy, ontogeny, and relationships of the Late Carboniferous tetrapod Gephyrostegus bohemicus Jaekel, 1902

ABSTRACT

We review the cranial morphology of the Late Carboniferous terrestrial tetrapod Gephyrostegus bohemicus from the coal deposits of the Nýřany Basin in the Czech Republic. Gephyrostegus is known from several skulls ranging in length from about 25 mm to about 58 mm (holotype). The narrow skull is about twice as long as wide and shows a well-ossified quadrate and articular, but no evidence of braincase ossification. Autapomorphic features include a pustular ornamentation on some skull table bones, and a plate-like tabular process exhibiting a fine dorsal pitting. Gephyrostegus shares with Bruktererpeton fiebigi (Late Carboniferous, Germany) the presence of low, anteromedially to posterolaterally orientated sharp ridges on the posteroventral surface of the vomer. It shares with seymouriamorphs a rectangular, transverse pterygoid process and closely packed, radially arranged rows of small denticles on the palate. A phylogenetic analysis retrieves Gephyrostegidae (Gephyrostegus, Bruktererpeton) as sister group to Seymouriamorpha, although this wider clade receives low bootstrap support.

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ACKNOWLEDGMENTS

We are very grateful to J. Müller (Museum für Naturkunde, Berlin) and A. C. Milner (The Natural History Museum, London) for producing high-quality casts, B. Ekrt (National Museum, Prague) and U. Göhlich (Natural History Museum, Vienna) for access to specimens, A. Čerňanský (Comenius University, Bratislava) for Figures 6 and 7, and I. Koubová (Bratislava) for Figure 4C. M. Ruta drew all other figures. K. Dobiašová (Comenius University, Bratislava) took the photographs in Figures 1A, 2A, 4A, and 5A. B. Ekrt took the photograph in Figure 3. We are indebted to our editor J. Anderson, and referees R. Holmes and S. Sumida, for their insightful reviews. Support was provided by the Scientific Grant Agency, Ministry of Education of the Slovak Republic, and the Slovak Academy of Sciences (grant no. 1/0131/12 to J.K.) and Natural Environment Research Council (Advanced Research Fellowship NE/F014872/1 to M.R.).

Handling editor: Jason Anderson.