A new genus and species of basal salamanders from the Middle Jurassic of Western Siberia, Russia

Abstract

A new basal stem salamander, Urupia monstrosa gen. et sp. nov., is described based on an atlantal centrum (holotype), fragments of trunk vertebrae, and some associated elements (fragmentary dentaries and a femur) from the Middle Jurassic (Bathonian) Itat Formation of Krasnoyarsk Territory in Western Siberia, Russia. The new taxon is characterized by the following combination of characters: lack of the spinal nerve foramina in the atlas, presence atlantal transverse processes and a deep depression on the ventral surface of the atlas; lateral surface of anterior part of the dentary is sculptured by oval and rounded pits; very short diaphyseal part of femur. The absence of intercotylar tubercle on the atlas and presence of atlantal transverse processes support for neotenic nature of Urupia monstrosa gen. et sp. nov. Large size, presence of sculpture on vertebrae, and the absence of spinal nerve foramina in the atlas suggest that Urupia monstrosa gen. et sp. nov. is a stem group salamander. The phylogenetic relationships of Urupia monstrosa gen. et sp. nov. with other stem group salamanders cannot be established on the available material.