Even-toed Ungulate - Evolutionary History

Evolutionary History

As with many mammal groups, even-toed ungulates first appeared during the Early Eocene (about 54 million years ago). In form, they were rather like today's chevrotains: small, short-legged creatures that ate leaves and the soft parts of plants. By the Late Eocene (46 million years ago), the three modern suborders had already developed: Suina (the pig group); Tylopoda (the camel group); and Ruminantia (the goat and cattle group). Nevertheless, artiodactyls were far from dominant at that time: the odd-toed ungulates (ancestors of today's horses and rhinos) were much more successful and far more numerous. Even-toed ungulates survived in niche roles, usually occupying marginal habitats, and it is presumably at that time that they developed their complex digestive systems, which allowed them to survive on lower-grade food.

The appearance of grasses during the Eocene, and their subsequent spread during the Miocene (about 20 million years ago), saw a major change; grasses are very difficult to eat and the even-toed ungulates, with their highly-developed stomachs, were better able to adapt to this coarse, low-nutrition diet, and soon replaced the odd-toed ungulates as the dominant terrestrial herbivores. Now-extinct Artiodactyla that developed during the Miocene include the genera Ampelomeryx, Tauromeryx, Triceromeryx.