Mammalia Linnaeus 1758 [Rowe 1988], nom. cl. inval. see Class Mammalia Linnaeus, 1758 Cetartiodactyla Montgelard, Catzeflis & Douzery 1997 see Order Cetartiodactyla Montgelard, Catzeflis & Douzery, 1997 Whippomorpha Waddell, Okada & Hasegawa 1999 see Suborder Whippomorpha Family Hippopotamidae Gray, 1821 - hippopotamuses