Hippopotamus amphibius; Print; The common hippopotamus; or hippo; is a large; mostly herbivorous; semiaquatic mammal and ungulate native to sub-Saharan Africa. It is one of only two extant species in the family Hippopotamidae; the other being the pygmy hippopotamus (Choeropsis liberiensis or Hexaprotodon liberiensis). The name comes from the ancient Greek for "river horse". After the elephant and rhinoceros; the common hippopotamus is the third-largest type of land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates; the closest living relatives of the Hippopotamidae are cetaceans (whales; dolphins; porpoises; etc.) from which they diverged about 55 million years ago.; intestines