Class Mammalia Linnaeus, 1758 - mammals Order Artiodactyla Owen, 1848 - even-toed ungulates see Order Cetartiodactyla Montgelard, Catzeflis & Douzery, 1997 Family Hippopotamidae Gray, 1821 - hippopotamuses 1 Genus Hexaprotodon Falconer & Cautley, 1836 2 Genus Hippopotamus Linnaeus, 1758 - hippopotamus