The common hippopotamus (Hippopotamus amphibius), or hippo, is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extantspecies in the family Hippopotamidae, the other being the pygmy hippopotamus(Choeropsis liberiensis or Hexaprotodon liberiensis). The name comes from theancient Greek for "river horse" (ἱπποπόταμος). After the elephant andrhinoceros, the common hippopotamus is the third-largest type of land mammaland the heaviest extant artiodactyl. Despite their physical resemblance to pigsand other terrestrial even-toed ungulates, their closest living relatives arecetaceans (whales, porpoises, etc.) from which they diverged about . The common ancestor of whales and hippos split from other even-toed ungulates around . The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around .
Common hippos are recognizable by their barrel-shaped torsos, wide-opening mouths revealing large canine tusks, nearly hairless bodies, columnar-like legs and large size; adults average 1,500 kg (3,300 lb) and 1,300 kg (2,900 lb) for males and females respectively, making them the largest species of land mammal after the 3 species of elephants and the white and Indian rhinoceros. Despite its stocky shape and short legs, it is capable of running 30 km/h