The members belonging to the order Perissodactyla are called odd-toed ungulates (ungulate is a general term denoting a group of mammals having hooves). Perissodactylids are medium to large sized mammals. These simple stomach animals have a large caecum. Nasals are broad at the posterior end. The true bony growths in terms of horns and antlers are not present. Two mammary glands are located in the inguinal region. The number of toes present in the perissodactylids varies according to the species. The tapirs have four toes on the forefoot and three on the hind. The rhinoceros, on the other hand, bear three toes on each foot. The horse, however, possesses one functional toe on each foot. With the exception of tapirs, all members of this order, therefore, either have one or three toes (hence called odd-toed ungulate) on each foot. All the members belonging to the order Perissodactyla are placed into the following three families: (a) Tapiridae - tapirs. (b) Rhinocerotidae - rhinoceros. (c) Equidae - horses, asses and zebras.