formerly, any hoofed mammal. Although the term is now used more broadly in formal classification as the grandorder Ungulata, in common usage it was widely applied to a diverse group of placental mammals (placental mammal) that were characterized as hoofed herbivorous quadrupeds. The feature that united them, the hoof, consists of hornlike dermal (skin) tissue, comparable to the human fingernail, which extends over the end of a broadened terminal digit.

Modern hoofed mammals comprise three groups: Artiodactyla (artiodactyl), the even-toed ungulates (swine, camels, deer, and bovines); Perissodactyla (perissodactyl), the odd-toed ungulates (horses, tapirs, and rhinoceroses); and Uranotheria, which includes the orders Proboscidea (proboscidean) (elephants), Hyracoidea (hyraxes (hyrax)), and Sirenia (sirenian) (manatees and dugongs).

The grandorder Ungulata also includes the orders Tubulidendata (aardvarks (aardvark)) and Cetacea (cetacean) (whales and dolphins). Nine orders of fossil ungulates are also recognized: Dinocerata (uintatheres), Procreodi, Condylarthra (condylarths), Arctostylopida, Litopterna (litopterns (litoptern)), Notoungulata (notoungulates, including the toxodonts (Toxodon)), Astrapotheria (astrapotheres), Xenungulata (xenungulates), and Pyrotheria (pyrotheres).