THE CRANIAL ANATOMY OF DISCOSAURISCUS KUHN, A SEYMOURIAMORPH TETRAPOD FROM THE LOWER PERMIAN OF THE BOSKOVICE FURROW (CZECH REPUBLIC)

摘要

A detailed description is given of the cranial anatomy of the Lower Permian tetrapod Discosauriscus. This material is three-dimensionally preserved and represents one of the best known seymouriamorph tetrapods. Two species, D. austriacus and D. pulcherrimus, are distinguished in the material from the Boskovice Furrow. D. austriacus is abundant, D. pulcherrimus is rare. The two species differ in the following features: in (1) the shape of the postorbital and the jugal and the nature of their junction, (2) the shape of the prefrontal and the postfrontal and the position of their contact and (3) the morphology of the ventral surfaces of the palatal bones and the arrangement of the denticles on them. The genus Discosauriscus represents larval, metamorphic and early juvenile individuals. Comparison of the cranial structures of Discosauriscus with those of Seymouria baylorensis, Seymouria sanjuanensis, and Seymouria cf. S. sanjuanensis (which is of similar size to the largest individuals of Discosauriscus) shows that (i) Discosauriscus and Seymouria are structurally similar but different genera, (ii) Discosauriscus is a member of the taxon Seymouriamorpha, (iii) Discosauriscus and Ariekanerpeton comprise the family Discosauriscidae and (iv) Seymouria is not a reptile (an amniote animal). Ariekanerpeton, Utegenia, Urumquia, kotlassiids, leptorophids and Enosuchus require revision. [References: 85]