New Data on the Morphology and Distribution of Kotlassia prima Amalitzky (Tetrapoda, Seymouriamorpha)

New data on the morphology and distribution of the kotlassiid Kotlassia prima Amalitzky (Seymouriamorpha) are provided based on fragmentary remains from five upper Permian localities in Eastern Europe. The new finds suggest the absence of a seismosensory system at the final stages of ontogeny in K. prima that may indicate a more terrestrial ecology for this species in the adult state in comparison with other late Permian representatives of the family (Microphon spp.), for which the paedomorphic features in the cranial and postcranial anatomy are common. The homodont dentition and the simple shape of the teeth allow interpretation of K. prima as a predator with a wide trophic niche, the prey of which was determined by resources of the specific biotopes and might include both invertebrates and relatively small vertebrates. The new finds show that K. prima was typical for tetrapod associations of the northeast of the East European Platform, extend the stratigraphic range of the genus Kotlassia up to the terminal Permian (Zhukovian), and indicate that the family Kotlassiidae maintained its taxonomic diversity until the Permo–Triassic cenotic crisis, continuing to play a significant role in vertebrate communities in the time preceding it.