Perissodactyl in the context of Chalicotheriidae

Artiodactyls are placental mammals belonging to the order Artiodactyla (/ˌɑːrtioʊˈdæktɪlə/ AR-tee-oh-DAK-tih-lə; from Ancient Greek ἄρτιος ártios 'even' and δάκτυλος dáktylos 'finger, toe'). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, most perissodactyls bear weight on an odd number of the five toes. Another difference between the two orders is that many artiodactyls (except for Suina) digest plant cellulose in one or more stomach chambers rather than in their intestine (as perissodactyls do). Molecular biology, along with new fossil discoveries, has found that cetaceans (whales, dolphins, and porpoises) fall within this taxonomic branch, being most closely related to hippopotamuses. Some modern taxonomists thus apply the name Cetartiodactyla (/sɪˌtɑːrtioʊˈdæktɪlə/) to this group, while others opt to include cetaceans within the existing name of Artiodactyla. Some researchers use "even-toed ungulates" to exclude cetaceans and only include terrestrial artiodactyls, making the term paraphyletic in nature.

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, and cetaceans are entirely carnivorous. Artiodactyls are also known by many extinct groups such as anoplotheres, cainotheriids, merycoidodonts, entelodonts, anthracotheres, basilosaurids, and palaeomerycids. Many artiodactyls are of great dietary, economic, and cultural importance to humans.

Artiodactyls are placental mammals belonging to the order Artiodactyla (/ˌɑːrtioʊˈdæktɪlə/ AR-tee-oh-DAK-tih-lə; from Ancient Greek ἄρτιος ártios 'even' and δάκτυλος dáktylos 'finger, toe'). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, most perissodactyls bear weight on an odd number of the five toes. Another difference between the two orders is that many artiodactyls (except for Suina) digest plant cellulose in one or more stomach chambers rather than in their intestine (as perissodactyls do). Molecular biology, along with new fossil discoveries, has found that cetaceans (whales, dolphins, and porpoises) fall within this taxonomic branch, being most closely related to hippopotamuses. Some modern taxonomists thus apply the name Cetartiodactyla (/sɪˌtɑːrtioʊˈdæktɪlə/) to this group, while others opt to include cetaceans within the existing name of Artiodactyla. Some researchers use "even-toed ungulates" to exclude cetaceans and only include terrestrial artiodactyls, making the term paraphyletic in nature, but since cetaceans have 0 toes, and 0 is an even number, they technically fit the label.

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, and cetaceans are entirely carnivorous. Artiodactyls are also known by many extinct groups such as anoplotheres, cainotheriids, merycoidodonts, entelodonts, anthracotheres, basilosaurids, and palaeomerycids. Many artiodactyls are of great dietary, economic, and cultural importance to humans.

Equus (/ˈɛkwəs, ˈiːkwəs/) is a genus of mammals in the perissodactyl family Equidae, which includes horses, asses, and zebras. Within the Equidae, Equus is the only recognized extant genus, comprising seven living species. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. The genus originated in North America and dispersed into the Old World and South America during the Early and Middle Pleistocene. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes (erect in most subspecies), and long tails. All species are herbivorous, and mostly grazers, with simpler digestive systems than ruminants but able to subsist on lower-quality vegetation.

While the domestic horse and donkey (along with their feral descendants) exist worldwide, wild equine populations are limited to Africa and Asia. Wild equine social systems are in two forms; a harem system with tight-knit groups consisting of one adult male or stallion/jackass, several females or mares/jennets, and their young or foals; and a territorial system where males establish territories with resources that attract females, which associate very fluidly. In both systems, females take care of their offspring, but males may play a role as well. Equines communicate with each other both visually and vocally. Human activities have threatened wild equine populations.

Palaeotheriidae is an extinct family of herbivorous perissodactyl mammals that inhabited Europe, with less abundant remains also known from Asia, from the mid-Eocene to the early Oligocene. They are classified in Equoidea, along with the living family Equidae (which includes zebras, horses and asses).

A rhinoceros (/raɪˈnɒsərəs/ ry-NOSS-ə-rəss; from Ancient Greek ῥινόκερως (rhinókerōs) 'nose-horned'; from ῥίς (rhis) 'nose' and κέρας (kéras) 'horn'; pl.: rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family Rhinocerotidae. It is the only living family in the superfamily Rhinocerotoidea (whose members are also sometimes called rhinoceroses). Two of the extant species are native to Africa, and three to South and Southeast Asia.

Rhinoceroses are some of the largest remaining megafauna: all weigh over half a tonne in adulthood. They have a herbivorous diet, small brains 400–600 g (14–21 oz) for mammals of their size, one or two horns, and a thick 1.5–5 cm (0.59–1.97 in), protective skin formed from layers of collagen positioned in a lattice structure. They generally eat leafy material, although their ability to ferment food in their hindgut allows them to subsist on more fibrous plant matter when necessary. Unlike other perissodactyls, the two African species of rhinoceros lack teeth at the front of their mouths; they rely instead on their lips to pluck food.

The hoof (pl.: hooves or hoofs) is the tip of a toe of an ungulate mammal, which is covered and strengthened with a thick and horny keratin covering. Artiodactyls are even-toed ungulates, species whose feet have an even number of digits; the ruminants with two digits are the most numerous, e.g. giraffe, deer, bison, cattle, goats, gazelles, pigs, and sheep. The feet of perissodactyl mammals have an odd number of toes, e.g. the horse, the rhinoceros, and the tapir. Although hooves are limb structures primarily found in placental mammals, hadrosaurs such as Edmontosaurus possessed hoofed hindlimbs. The marsupial Chaeropus also had hooves.

Hyracotherium (/ˌhaɪrəkoʊˈθɪəriəm, -kə-/ HY-rək-o-THEER-ee-əm; "hyrax-like beast") is an extinct genus of small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, fox-sized animal is (for some scientists) considered to be the earliest known member of Equidae before the type species, H. leporinum, was reclassified as a palaeothere, a perissodactyl family related to both horses and brontotheres. The remaining species are now thought to belong to different genera, such as Eohippus, which had previously been synonymised with Hyracotherium.