The systematic arrangement of the order Perissodactyla

There is a graduated series, with successive modifications of four parts of the skeleton: 1. reduction of the number of toes on anterior foot 2. reduction in the number and development of the canine and incisor teeth 3. degree of closure of the meatus auditorius externus below 4. development of the dermal horns on the nose and its supports. Coelodonta Rhinoceros Atelodus Ceratorhinus Peraceras Aphelops Zalabis Coenopus Diceratherium End

Rhinoceridae