Hippopotamus Hippopotamus The common hippopotamus ("Hippopotamus amphibius"), or hippo, is a large, mostly herbivorous, semiaquatic mammal native to sub-Saharan Africa, and 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
Common species Common species Common species and uncommon species are designations used in ecology to describe the population status of a species. Commonness is closely related to abundance. Abundance refers to the frequency with which a species is found in controlled samples; in contrast, species are defined as common or uncommon based on their overall presence in the environment. A species may be locally abundant without being common. However, "common" and "uncommon" are also sometimes used to describe levels of abundance, with a common species being less abundant than an abundant species, while an uncommon species is more abundant than a rare