Ancient Species of the Genus <i>Dvinosaurus</i> (Temnospondyli, Dvinosauria) from the Permian Sundyr Tetrapod Assemblage of Eastern Europe

From the Sundyr-1 reference locality of the Sundyr faunal assemblage of Eastern Europe (Upper Permian, Upper Severodvinian Substage, Suchonica vladimiri Assemblage Zone), the oldest species of the genus Dvinosaurus Amalitzky, 1921 Dvinosaurus gubini sp. nov. The diagnostic criterions for the new species are its smaller size compared to other dvinosaurs, the narrowest skull, short and wide zygomatic bone, parasphenoid body with a more wide base of the cultriform process and a well ossified basisphenoid, a strongly curved dentary with a well-defined symphyseal crest extending downward from the labial side of the symphysis and, in a several cases, with a single symphyseal canine, a large angle (135–152°) between the clavicular plate and the dorsal process of the clavicle, narrow areas of the interclavicle for insertion of the clavicles, narrow entepicondylus of the humerus. The size, narrowness of the skull, the presence of a single symphyseal canine, and hypocentrum structure bring together a new form closer to the basal Dvinosauria, in particular, with ancestral Trimerorhachidae.