Mesonychia

Mesonychia ("middle claws") is an extinct taxon of small to large-sized carnivorous ungulates related to artiodactyls. Mesonychians first appeared in the Early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely when the last genus, Mongolestes, became extinct in the Early Oligocene. In Asia, the record of their history suggests they grew gradually larger and more predatory over time, then shifted to scavenging and bone-crushing lifestyles before the group became extinct.

Mesonychians probably originated in China, where the most primitive mesonychian, Yantanglestes, is known from the early Paleocene. They were also most diverse in Asia, where they occur in all major Paleocene faunas. Since other predators, such as creodonts and Carnivora, were either rare or absent in these animal communities, mesonychians most likely dominated the large predator niche in the Paleocene of eastern Asia.