A large, heavily built, odd-toed ungulate (order Perissodactyla, family Rhinocerotidae), with skin up to 5 cm thick, a small brain, a narrow muzzle, and one or two horns on the snout made from keratin. Rhinoceroses are killed illegally for their horns, which have ornamental and medicinal uses in some cultures. There are four genera with five species. The white (Ceratotherium simum) and black (Diceros bicornis) rhinoceroses occur in central and southern Africa, the Indian (Rhinoceros unicornis), Javan (R. sondaicus), and Sumatran (Dicerorhinus sumatransis) in Asia.