From Wikipedia: The rhinoceros (meaning "nose horn"), often abbreviated to rhino, is one of any five extant species of odd-toed
ungulates in the family Rhinocerotidae, as well as any of the numerous extinct species. Two of these extant species are native to
Africa and three to Southern Asia.
Members of the rhinoceros family are characterized by their large size (they are some of the largest remaining megafauna, with
all of the species able to reach one ton or more in weight); as well as by an herbivorous diet; a thick protective skin, 1.5–5 cm thick,
formed from layers of collagen positioned in a lattice structure; relatively small brains for mammals this size (400–600 g); and a
large horn. They generally eat leafy material, although their ability to ferment food in their hindgut allows them to subsist on more
fibrous plant matter, if necessary. Unlike other perissodactyls, the two African species of rhinoceros lack teeth at the front of their
mouths, relying instead on their lips to pluck food.
The two African species, the white rhinoceros and the black rhinoceros, belong to the tribe Dicerotini, which originated in the middle
Miocene, about 14.2 million years ago. The species diverged during the early Pliocene (about 5 million years ago). The main difference
between black and white rhinos is the shape of their mouths – white rhinos have broad flat lips for grazing, whereas black rhinos have
long pointed lips for eating foliage.