The even-toed ungulates are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two is that many other even-toed ungulates (with the exception of Suina) digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do.
Cetaceans (whales, dolphins, and porpoises) evolved from even-toed ungulates, so some modern taxonomists combine the two under the name Cetartiodactyla. Others opt to include cetaceans in the already-existing Artiodactyla.
The roughly 270 land-based even-toed ungulate species include pigs, peccaries, hippopotamuses, antelopes, deer, giraffes, camels, llamas, alpacas, sheep, goats, and cattle. Many are herbivores, but suids are omnivorous, while cetaceans are almost exclusively carnivorous. Many of these are of great dietary, economic, and cultural importance to humans.
Artiodactyls are native to almost all parts of the world, with the exception of Oceania and Antarctica. Humans have introduced different artiodactyls worldwide as hunting animals. Artiodactyls inhabit almost every habitat, from tropical rainforests and steppes to deserts and high mountain regions. The greatest biodiversity prevails in open habitats such as grasslands and open forests.