The hippopotamus is a large amphibious, herbivorous mammal. It is characterized by large canines, a long body, and a long snout. After the elephant and rhinoceros, the hippo is the third largest land mammal and is the heaviest Artiodactyl (even-toed Ungulate). While hippos may look a lot like rhinos, they are closely related to the whales, dolphins, porpoises, dugongs, and manatees. The main hippo clades were Pakicetids, Anthracotheres, and Desmostylas. The first hippo relative was probably Pakicetus. It was then followed by Elomeryx, Anthracotherium, Merycopotamus, Libycosaurus, Desmostylus, Behemotops, Cornwallius, Paleoparadoxia, Kronokotherium, Kenyapotamus,and Archaeopotamus.