The skull of hippos is relatively large and elongated, and the braincase is small. The orbits are high up on the skull. Hippos have a well developed sagittal crest and occipital ridges, and an incomplete postorbital bar. The foot bones are unfused and all four toes of each foot are functional and support the body. The lateral digits are nearly as well developed as the central ones. Hippos are digitigrade, but only the distal phalanx of each toe actually touches the ground, and the rest of the foot is braced by a pad of connective tissue. The stomach has three chambers but is non-ruminating.
The number of incisors is variable within both species and a general dental formula for the family is 2-3/1-3, 1/1, 4/4, 3/3 = 38-44. The tusk-like incisors and canines grow continuously. The lower incisors are longer than the uppers and project forward. The lower canines are the largest of the tusk-like teeth and curve up above the upper tooth row. The cheek teeth are progressively more complex toward the back of the jaw. The premolars are usually have single cusps, though this varies. The molars have two or three pairs of cusps which wear down to a trefoil, figure-eight and dumbbell-shaped enamel figures. They are bunodont.
Hippos are gregarious animals, living in herds of up to 40 animals. They are amphibious and excellent swimmers, spending much of the day in the water and emerging in the evening to feed on terrestrial vegetation. They also eat aquatic plants, which they may obtain by diving and swimming entirely submerged. Their terrestrial foraging areas may be several kilometers distant from where they pass the day, and they sometimes are responsible for considerable damage to crops and rangelands due to their foraging and their travel to foraging areas. Pygmy hippos are less social and are usually found in forested areas.
The historic range of both species included all of sub-Saharan Africa, the Nile river, Palestine and even Madagascar. Fossil hippos are known from late Miocene to late Pleistocene deposits in Europe, Asia and Africa.
 The Hippopatamus |
 The pygmy Hippopatamus |
 hippos drinking |
 classic hippo |
Family Suidae Family Tayassuidae Family Hippopotamidae Family Camelidae Family Tragulidae Family Giraffidae Family Moschidae Family Cervidae Family Antilocapridae Family Bovidae<<<<<<<>>>>>>> ARTIODACTYLA CARNIVORA CETACEA CHIROPTERA DASYUROMORPHIA DERMOPTERA DIDELPHIMORPHI DIPROTODONTIA HYRACOIDEA INSECTIVORA LAGOMORPHA MACROSCELIDEA MICROBIOTHERIA MONOTREMATA NOTORYCTEMORPHIA PAUCITUBERCULATA PERAMELEMORPHIA PERISSODACTYLA PHOLIDOTA PRIMATES PROBOSCIDEA RODENTIA SCANDENTIA SIRENIA TUBULIDENTATA XENARTHRA
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