Abstract
Hapalodectes paradux sp. nov. (Hapalodectidae, Mesonychia) is described on the base of the dentary fragment with M(2)-M(3) from the Tsagan-Khushu locality in Mongolia (Upper Paleocene, Naran Bulak Formation, Zhigden Member). The M(2) and M(3) are approximately the same size, with a high protoconid, anteriorly displaced reduced metaconid, anterolingually directed protocristid, very deep posterior notch, narrow talonid, and distinct hypoconid, entoconid and hypoconulid. Based on dental characters, the new species is presumably related to the base of the lineage of Hapalodectes that dispersed to North America at the beginning of the Eocene. Tsagan-Khushu is the only known locality where two species of Hapalodectes co-occur (larger H. dux Lopatin, 2001 and smaller H. paradux sp. nov.).