A large group of ungulates has an even number of toes on its feet, either 2 or 4. These ungulates include camel relatives, swine relatives, the hippos and the ruminants. This gallery shows examples of the first three groups. All of the animals shown here have multiple chambers in their stomachs, usually three. The two toes that bear their weight correspond to the middle and fourth toes of their five-toed ancestors. The other toes are reduced, or missing.
The 7 camel relatives include the camels themselves (3 species), the llamas (the wild guanaco and the domestic llama), and the alpacas (the wild vicuna and the domestic alpaca). The camelids have two toes with toenails on each foot. The camelids are adapted to areas with little water, obtaining the water that they need primarily from the vegetation that they eat. They are also adapted to high altitudes, with blood that retains more oxygen than other mammals. Differences from other mammals also include: the musculature of their hind legs, the arrangement of their teeth, and their split lips.
Only two species of hippo exist today — the common hippo and the pygmy hippo. Hippos are semi-aquatic. Due to their very sparse hair, they must spend time in the water to avoid drying out their skin. The hippopotamus is the closest living relative of the cetaceans (whales and dolphins). Both groups share webbed feet (or fins) with four toes, single-lobed lungs, and a unique larynx designed to project sound underwater.
The swine are medium-sized ungulates with large heads, a short neck and a body covered with short bristly hair. The peccaries (4 species) evolved in North America and are found in North and South America today. They represent the oldest lineage of the swine and have the three-chambered stomachs. The swine relatives also include 19 species of pigs that evolved in Asia, but are now distributed world-wide. The pigs have one main stomach chamber and reduced other chamber.