Abstract: Early Paleogene mesonychid specimens, recently collected from the Huheboerhe area and Bayan Ulan, eastern Erlian Basin, Nei Mongol (Inner Mongolia), are described in this paper. They represent six species and four genera, a few of the specimens are specifically indeterminate. Mesonyx nuhetingensis sp. nov., from the basal Arshanto Formation, differs from previously known species of Mesonyx in p4 being the longest lower cheek tooth and weak lingual cingula being present on p3 and p4, respectively. Other mesonychid specimens described in this paper are referred toDissacus serratus, Dissacus sp., Mesonyx uqbulakensis, Mongolonyx dolichognathusand Harpagolestes leei. General evolutionary trends seen in mesonychids from theErlian Basin show a gradual increase in body size and a change in feeding habits from active predation to scavenging.