The Artiodactyla are even-toed ungulates, an order of mammals. They have an even number of toes: two or four. For example, camelids or animals of the Giraffidae family have two toes, but hippopotami have four toes.
Whales are ocean creatures without toes, but are classified in the related super-order Cetartiodactyla because their ancestors were even toed ungulates.
Digestion
Some artiodactyls are ruminants (Ruminantia and Tylopoda). They ruminate their food—they regurgitate and re-chew it. This is a very important evolutionary advance. Their stomachs are divided into three to four sections.
After eating, the food re-enters the mouth, where it is chewed again. The food passes to the "fermentation chamber" (rumen and reticulum), where microbes (bacteria, protozoa, and fungi) help to break down the cellulose found in plant material.
This form of digestion has two advantages: ruminants can digest plants that are indigestible to other species, and they can take less time in eating. The animal spends only a short time out in the open with his head to the ground—rumination can happen later, in a sheltered area.