Perissodactyla is an order of ungulates. The order includes about 17 living species divided into three families: Equidae, Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They typically have reduced the weight-bearing toes to three or one of the five original toes, though tapirs retain four toes on their front feet. The nonweight-bearing toes are either present, absent, vestigial, or positioned posteriorly. By contrast, artiodactyls bear most of their weight equally on four or two of the five toes: their third and fourth toes. Another difference between the two is that perissodactyls digest plant cellulose in their intestines, rather than in one or more stomach chambers as artiodactyls, with the exception of Suina, do.
The quagga is an extinct subspecies of the plains zebra that was endemic to South Africa until it was hunted to extinction in the late 19th century. It was long thought to be a distinct species, but early genetic studies have supported it being a subspecies of plains zebra. A more recent study suggested that it was the southernmost cline or ecotype of the species.
Zebras are African equines with distinctive black-and-white striped coats. There are three living species: Grévy's zebra, the plains zebra, and the mountain zebra. Zebras share the genus Equus with horses and asses, the three groups being the only living members of the family Equidae. Zebra stripes come in different patterns, unique to each individual. Several theories have been proposed for the function of these stripes, with most evidence supporting them as a deterrent for biting flies. Zebras inhabit eastern and southern Africa and can be found in a variety of habitats such as savannahs, grasslands, woodlands, shrublands, and mountainous areas.
The onager, also known as hemione or Asiatic wild ass, is a species of the family Equidae native to Asia. A member of the subgenus Asinus, the onager was described and given its binomial name by German zoologist Peter Simon Pallas in 1775. Six subspecies have been recognized, two of which are extinct.
The plains zebra is the most common and geographically widespread species of zebra. Its range is fragmented, but spans much of southern and eastern Africa south of the Sahara. Six or seven subspecies have been recognised, including the extinct quagga which was thought to be a separate species. More recent research supports variations in zebra populations being clines rather than subspecies.
Equus is a genus of mammals in the 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 most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes, and long tails. All species are herbivorous, and mostly grazers, with simpler digestive systems than ruminants but able to subsist on lower-quality vegetation.
The kiang is the largest of the Asinus subgenus. It is native to the Tibetan Plateau in Ladakh, northern Pakistan, Tajikistan, China and northern Nepal. It inhabits montane grasslands and shrublands. Other common names for this species include Tibetan wild ass, khyang and gorkhar.
Grévy's zebra, also known as the imperial zebra, is the largest living wild equid and the most threatened of the three species of zebra, the other two being the plains zebra and the mountain zebra. Named after Jules Grévy, it is found in parts of Kenya and Ethiopia. Superficially, Grévy's zebras' physical features can help to identify it from the other zebra species; their overall appearance is slightly closer to that of a mule, compared to the more "equine" (horse) appearance of the plains and mountain zebras. Compared to other zebra species, Grévy's are the tallest; they have mule-like, larger ears, and have the tightest stripes of all zebras. They have distinctively erect manes, and more slender snouts.
The wild asses (Asinus) are a subgenus of single toed grazing ungulates. Its species are:
The Mongolian wild ass, also known as Mongolian khulan, is the nominate subspecies of the onager. It is found in southern Mongolia and northern China. It was previously found in eastern Kazakhstan and southern Siberia before being extirpated there through hunting. As of 2015, the Mongolian wild ass is listed as Near Threatened by the IUCN. Current population estimates are approximately 42,000 individuals in Mongolia and around 5,000 individuals in Northern China.
The African wild ass or African wild donkey is a wild member of the horse family, Equidae. This species is thought to be the ancestor of the domestic donkey, which is sometimes placed within the same species. They live in the deserts and other arid areas of the Horn of Africa, in Eritrea, Ethiopia and Somalia. It formerly had a wider range north and west into Sudan, Egypt, and Libya. It is Critically Endangered, with about 570 existing in the wild.
Grant's zebra is the smallest of the seven subspecies of the plains zebra. This subspecies represents the zebra form of the Serengeti-Mara ecosystem and others across central Africa.
The European wild ass or hydruntine is an extinct equine from the Middle Pleistocene to Late Holocene of Europe and West Asia, and possibly North Africa. It is a member of the subgenus Asinus, and closely related to the living Asiatic wild ass. The specific epithet, hydruntinus, means from Otranto.
Asinus is a subgenus of Equus that encompasses several subspecies of the Equidae commonly known as wild asses, characterized by long ears, a lean, straight-backed build, lack of a true withers, a coarse mane and tail, and a reputation for considerable toughness and endurance.
Hippidion is an extinct genus of equine that lived in South America from the Late Pliocene to the end of the Late Pleistocene (Lujanian), between 2.5 million and 11,000 years ago. They were one of two lineages of equines native to South America during the Pleistocene epoch, alongside Equus (Amerhippus) neogeus.
The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the modern horse than of any other animal. Much of this evolution took place in North America, where horses originated but became extinct about 10,000 years ago, before being reintroduced in the 15th century.
The Turkmenian kulan, also called Transcaspian wild ass, Turkmenistani onager or simply the kulan, is a subspecies of onager native to Central Asia. It was declared Endangered in 2016.
Equus stenonis is an extinct species of equine that lived in Western Eurasia during the Early Pleistocene epoch.
Equus ovodovi is an extinct species of equine known from the Late Pleistocene and Holocene of North and East Asia.
