Mesonyx ("middle claw") is a genus of extinct, superficially wolf-like mesonychid mesonychian mammal: fossils of the various species are found in Early to Latee Eocene-age strata in the United States and Early Eocene-aged strata in China, 51.8—51.7 Ma (AEO). Mesonyx measured about 1.5 m (5 ft) long not including the tail, and weighted an estimated 22.7–34 kg.