Ungulate is a term used to refer to any type of hoofed mammal. Deer, antelope, horses, and llamas are all examples of ungulates, which can be distinguished because they walk on their toes, which have hardened into hooves through millennia of evolution. Ungulate evolution favored fast moving animals with long legs well adapted to living on grassy plains and savannahs.
There are three to four orders of animal which are classified as ungulates, including even-toed ungulates, odd-toed ungulates, and elephants. Some biologists include a fourth order, the Hyracoidea, as well. They share a common ancestor, and can be found on almost every continent of the world. Other animals on Earth including many ocean going mammals share an ancestor with ungulates, but they are not classified as such because they lack distinctive hooves.
The even-toed ungulates are known as the Artiodactyla, and include goats, pigs, and sheep. Most even-toed ungulates have split hooves which face forward. Additional digits have shrunk and moved to the back of the foot as the animals evolved. In some animals, these extra digits have disappeared entirely, as is the case with the rhinoceros. This ungulate group is the largest, with one hundred living species.
An odd-toed ungulate is known as a member of the Perissodactyla, a much smaller ungulate division. The Perissodactyla is broken into three groups, which together contain 17 living species, although the fossil record indicates that this ungulate group was once much larger. The three groups are rhinoceroses, horses, and tapirs. The rhinoceroses and tapirs walk on three toes, while horses have only one.
The third ungulate group is the elephants, which are a part of a much larger group of animals. Some biologists also classify the Hyracoidea as ungulates. The Hyracoidea are rodents like mammals found in Africa and Asia which walk on the tip of their toes like other ungulates. These animals are more informally known as hyraxes, an inclusive name for fourteen individual species of the animals.
The role of ungulates in human history is very important. Some of the earliest domesticated animals such as goats and sheep are ungulate species. Humans have used ungulates to provide meat, milk, and fiber for thousands of years. Ungulate species such as horses were ridden by many ancient cultures and continue to be used for recreation and transportation today.