A lepidosauromorph specimen from the Middle Jurassic (Bathonian) Moskvoretskaya Formation of the Moscow Region, Russia

A fragmentary diapsid left maxilla from the Bathonian Peski locality in Moscow Region, previously referred to Choristodera, is identified as Lepidosauromorpha indet. This specimen represents the first fossil record of basal lepidosauromorphs in the Middle Jurassic of European Russia. Among basal lepidosauromorphs, the maxilla from the Peski locality resembles those of the Middle Triassic Fraxinisaura and the contemporary Middle Jurassic (Bathonian) Marmoretta in subpleurodont tooth implantation, a relatively low dorsal process, and high keeled teeth with gently recurved apices and striae on the lingual side. This similarity suggests possible close relationships of Fraxinisaura, Marmoretta and the Peski form. The recognition of a basal lepidosauromorph in the fauna of the Peski locality extends the known geographical range of the Bathonian non-lepidosaurian lepidosauromorphs and demonstrates their wide Laurasian distribution at this time. It is additional evidence that Bathonian vertebrate faunas of Europe and Western Siberia were similar in composition