THE OLDEST DRYOLESTID MAMMAL FROM THE MIDDLE JURASSIC OF SIBERIA

Anthracolestes sergeii, gen. et sp. nov., based on three isolated lower molars and several edentulous dentary fragments from the Middle Jurassic (Bathonian) Itat Formation at Berezovsk Quarry in Krasnoyarsk Territory, Russia, is the oldest and most basal representative of Dryolestidae. It shows four unambiguous synapomorphies of Dryolestidae: lower molars with unilaterally hypsodont crowns, unequal roots, and pronounced precingulid instead of cusp f, and dentary with unequal alveolar borders. The dental formula of the new taxon is i1-4, c (double-rooted), p1-4(?), and m1-4(?). Anthracolestes sergeii, gen. et sp. nov., is plesiomorphic relative to more derived and geologically younger dryolestids in having possibly fewer lower molars, less pronounced mesiodistal compression of lower molars, oblique protocristid, short mandibular symphysis, and shallow mandibular ramus of the dentary. Asia is most likely the place of origin for Dryolestidae, but this group is so far not known from that continent after the Middle Jurassic.