Class Mammalia Linnaeus, 1758 - mammals Order Artiodactyla Owen, 1848 - even-toed ungulates see Order Cetartiodactyla Montgelard, Catzeflis & Douzery, 1997 Family Hippopotamidae Gray, 1821 - hippopotamuses Genus Hippopotamus Linnaeus, 1758 - hippopotamus 1 Hippopotamus amphibius Linnaeus, 1758 - hippopotamus 2 ‡Hippopotamus lemerlei Grandidier, in Milne-Edwards, 1868