A new docodont (Mammalia) from the Middle Jurassic of Kyrgyzstan, central Asia

Abstract

ABSTRACT Tashkumyrodon desideratus, gen. et sp. nov. from the Middle Jurassic (Callovian) Balabansai Formation near Tashkumyr in Kyrgyzstan is described from a single lower molar. The tooth exhibits the typical structure of a docodont lower molar with the main cusp a connected by crests to the lingual cusps (c and g) and to the mesial cusp b. Tashkumyrodon is plesiomorphic in retaining well developed crests c-d and d-f, and derived in reduction of crest b-g. By formation of crests b-e and e-g (derived), Tashkumyrodon resembles Tegotherium from the Late Jurassic of Mongolia and Sibirotherium from the Early Cretaceous of West Siberia, Russia. Tegotherium is more derived than Tashkumyrodon by the more prominent anterior basin (“pseudotalonid”) and the reduction of the crests distal to cusp c. The Asian docodonts probably represent the sister group of all remaining docodonts, an Euramerican clade characterized by retention of crest b-g and reduction of cusp e as well as crest b-e. Simpsonodon from the Middle Jurassic of England is convergently similar to Tegotherium in development of a “pseudotalonid” and reduction of distal crests.