Prehistoric rhinos: Horny or Not?

Black Rhino (Diceros bicornis), Pittsburgh Zoo

It might seem strange, but the first members of the rhino family to appear on the evolutionary scene some 40 million years ago were hornless. Paleontologists place them in the Family Rhinocerotidae based on similarities in dentition, especially tusk-like incisors that remain prominent in today’s greater one-horned and Javan rhinos from Asia. Interestingly enough, both present-day African species – white and black rhinos – have lost their incisor teeth entirely.

Fossil rhinos of the North American genus Menoceras possessed two horns, the same as the two African species and the Sumatran rhino. However, instead of one horn being located in front of the other, the two horns were situated side by side. And only the males had them, the same as in Javan rhinos today!