; suborder Ceratomorpha, superfamily Rhinoceratoidea)
A family that includes the rhinoceroses and their fossil relatives. They were derived from the Hyracodontidae (‘running rhinoceroses’) in the Eocene and were prominent in the Oligocene, producing a variety of different types. They are characterized by the molarization of the premolars, the enlargement of the first upper and second lower incisors as cutting teeth (subsequently lost in some lines) and the consequent development of a pointed lip and narrow muzzle, and a simple last upper molar. The skeleton is similar to that of elephants, having vertebrae with long neural spines and many ribs so the spine and ribs together form a weight-bearing ‘girder’ resting on the fore limbs and counterbalanced by the weight of the head. All later rhinoceroses have three digits on each limb, but early forms had four. Probably early forms were hornless. While all rhinoceroses tended to large size, some aberrant forms became very large indeed. Paraceratherium (formerly Baluchitherium), a hornless form which lived in Asia during the Oligocene, was about 5.5 m tall at the shoulder, had a long neck and a skull about 1.2 m long, and must have weighed about 20 tonnes, making it the largest land mammal ever to have lived. Elasmotherium, which may have possessed a very large horn, was also a large form which lived on the Eurasian plains during the Pleistocene. Coelodonta was the woolly rhinoceros which lived during the Pleistocene. Today there are four genera, and five species: Rhinoceros unicornis, the one-horned Indian form; R. sondaicus, the related Javan species (now very rare); Dicerorhinus sumatrensis, the rare two-horned Sumatran form; and the African rhinoceroses Diceros bicornis (black) and Ceratotherium simum (white).
Subjects: Zoology and Animal Sciences.