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.

Hapalodectidae (literal translation 'soft biters': ('soft, tender'), ('biter')) is an extinct family of relatively small-bodied () mesonychian placental mammals from the Paleocene and Eocene of North America and Asia. Hapalodectids differ from the larger and better-known mesonychids by having teeth specialized for cutting (presumably meat), while the teeth of other mesonychids, such as Mesonyx or Sinonyx, are more specialized for crushing bones. Hapalodectids were once considered a subfamily of the Mesonychidae, but the discovery of a skull of Hapalodectes hetangensis showed additional differe

Triisodontidae is an extinct, probably paraphyletic, or possibly invalid family of mesonychian placental mammals. Most triisodontid genera lived during the Paleocene in North America, but the genus Andrewsarchus (if it is a mesonychian, and not an artiodactyl) is known from the middle Eocene of Asia. Triisodontids were the first relatively large predatory mammals to appear in North America following the extinction of the non-bird dinosaurs. They differ from other mesonychian families in having less highly modified teeth.

Hapalodectes (literal translation 'soft biter'; from ('soft, tender') and ('biter')) is an extinct genus of otter-like mesonychians from the Late Paleocene to Early Eocene, some 55million years ago. Although the first fossils were found in the Eocene strata of Wyoming, the genus originated in Mongolia, as the oldest species is H. dux, which was found in Late Paleocene strata in the Naran Bulak Formation. left|thumb|Life restoration of H. serus The genus was once suggested to be related to the Archaeoceti, such as Pakicetus, due to numerous similarities between the skull and tooth anatomies of

Triisodon (ancient Greek: "Tri" (three),"isos" (equal), and modern Greek: "donti" (tooth/teeth), supposedly describing tritubercular lower cheek teeth) is a genus of extinct mesonychian mammal that existed during the Early Paleocene of New Mexico, North America, from about 63.5-62.0 Ma. The genus was named by Edward Drinker Cope in 1881 as a member of the Acreodi, a now invalid taxon that encompassed creodonts, mesonychians and certain arctocyonians. Cope described the type specimen of T. quivirensis as "about the size of a wolf." A smaller species, T. crassicuspis, has also been identified fr

Eoconodon is an extinct genus of triisodontid mesonychian that existed during the early Paleocene of North America. Characteristics of the genus include massive jaws, blunt builds, and strong canine teeth. thumb|left|E. coryphaeus jaw Eoconodon is considered to be a giant for mammals during the Early Paleocene, with E. coryphaeus weighing up to .