A New Leptoropha (Kotlassiidae, Seymouriamorpha) Species from the Upper Urzhumian of European Russia

A new species of the genus Leptoropha (Kotlassiidae, Seymouriamorpha), L. minima sp. nov, is described based on isolated teeth discovered in the Upper Urzhumian beds of the boundary stratotype of the Severodvinian Stage (Republic of Tatarstan, Russia). A sample from the type locality (Monastyrskii Ovrag-D) enabled the tracing of the modification of maxillar and mandibular tooth shape in individuals with skull lengths of 30–60 mm, from the tricuspid pattern to complex polycuspid fan-shaped crowns with a large (up to 14) number of complementary cusps that definitively formed the marginal portions of the protocingulum in the anteriormost jaw teeth. In addition to the type locality, individual teeth attributed to L. minima were identified from the Upper Urzhumian of the Southern Cis-Ural Region (Orenburg Region, Yashkino locality) and the lowermost Severodvinian beds of the Vyatka River basin (Kirov Region, Povoiska locality); findings of teeth of similar morphology at the Sundyr-1 locality (Mari El Republic, Russia) extend the stratigraphic distribution of Leptorophinae to the Upper Severodvinian (Lower Putyatinian) and indicate the presence of the group in the last fauna of the Dinocephalian Tetrapod Superassemblage of Eastern Europe, the Sundyr’ Tetrapod Assemblage.