Artiodactyla or Even Toed Ungulates is an order of ungulates—hoofed mammals—which typically 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, known as perissodactyls, bear weight on one (an odd number) of the five toes: the third toe. Another difference between the two is that even-toed ungulates digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do.
The aquatic cetaceans (whales, dolphins, and porpoises) evolved from even-toed ungulates, so modern taxonomic classification places Cetacea within the order.
The roughly 270 land-based even-toed ungulate species include pigs, peccaries, hippopotamuses, antelopes, mouse deer, deer, giraffes, camels, llamas, alpacas, sheep, goats, and cattle. Many of these are of great dietary, economic, and cultural importance to humans. Their oldest fossil dates back to the Eocene.