Enigmatic ungulate-like mammals from the Eocene of Central Asia.

A new mammal family, Olseniidae, is proposed based on a complete foot skeleton of cf. Olsenia sp. from the Eocene Toru Ajgyr locality in Kyrgyzstan and an astragalus of Olsenia mira from the Eocene Shara Murun locality in northern China. The new form cf. Olsenia sp. is an early ungulate that combines characteristics of mesonychids, perissodactyls and artiodactyls: tetradactyl and paraxonic foot, terminal phalanges claw-like but not fissured, astragalus with shallow proximal caput and without distal trochlea. This unique character set fills a gap in the fossil record and gives insights into the ungulate phylogeny, which is still not completely understood.