Hippo Classification

Class

• The hippopotamus belongs to the class mammalia, which includes all of the nearly 5,000 mammals. Members of this class have three inner ear bones, commonly called the hammer, anvil and stirrup, that move vibrations to the eardrum. Female mammals produce milk through their mammary glands. All members of the class mammalia also have hair on at least some parts of their body. Hippopotami have sparse hairs so they rely on mud and water to keep them protected from the sun.

Order

• Of the 26 orders within the class mammalia, the hippopotamus belongs to Artiodactyla. Members of the order Artiodactyla usually have either two or four feet with hooves. These species live on six continents, where they make up the majority of domesticated animals and large wild mammals. The animals within this order vary in every way but their foot structure, including habitats, size, color and behaviors. Artiodactyla members include pigs, reindeer, camels, sheep and giraffes. The exception to the rule is dolphins and whales, which evolved to lose their legs.

Suborder

• Until recently, the hippopotamus belonged to the suborder suiformes, because researchers believed pigs were their closest relative. However, genetic research concludes that the hippopotamus is more closely related to dolphins and whales than any other hoofed mammal. Thus, biologists created a new suborder to group the hippopotamus with its closest living relatives. Whales, dolphins and hippopotami belong to the suborder cetancodonta, even though the hippopotamus bears little physical resemblance to the aquatic mammals.

Family, Genus and Species

• The hippopotamus belongs to the aptly named family Hippopotamidae. This family only consists of the two types of hippopotami: the common hippopotamus and the pygmy hippopotamus. The pygmy hippopotamus has a genus and species of Hexaprotodon liberiensis, while the common hippopotamus, or river hippopotamus, has the genus and species Hippopotamus amphibious. Biologists haven't created any subspecies of hippopotamus, but historical evidence suggests that some biologists have previously separated the species with criteria that no one knows anymore.