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Equus (genus)
Encyclopedia
Equus is a genus
of animals in the family
Equidae
that includes horse
s, donkey
s, and zebra
s. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species
known only from fossil
s. This article deals primarily with the extant species.
The term equine refers to any member of this genus, including any horse
. The word comes from Latin
equus, "horse", cognate with Greek
"ἴκκος" (ikkos), "horse" (the earliest form of the word is the Mycenaean Greek i-qo, written in Linear B
syllabic script).
s, with long heads, and necks with a mane
. Their legs are slender and end in a single, unguligrade toe, protected by a horny hoof
. They have long, slender, tails, either ending in a tuft, or entirely covered in flowing hair. They are adapted to generally open terrain, from plain
s and savanna
s, to mountains or desert
s.
The pinnae (outer ears) of equines are mobile, enabling them to easily localise the origin of sounds. They have two-color, or dichromatic vision. Their eyes are set back far on the head, giving them a wide angle of view, without entirely losing binocular vision
. Equines also have a vomeronasal organ
, that allows males to use the flehmen, or 'lip-curling' response to assess the sexual state of potential mates. Equines are one of only two mammals (the other is the human) capable of producing copious sweat perspiration for thermoregulatory cooling, enabling fast running over long distances.
Equines are herbivore
s, and feed predominantly on tough, fibrous food, such as grass
es and sedges. When in need, they will also eat other vegetable matter, such as leaves, fruits, or bark, but are normally grazers, not browsers. Unlike ruminant
s, with their complex stomachs, equines break down cellulose
in the "hindgut" or caecum, a part of the colon
. Their dentition is almost complete, with cutting incisor
s to crop food, and grinding molars set well back behind a diastema
. The dental formula for equines is:
Equines are social animals, living in herds or bands. Horses, along with Plains and Mountain Zebras, have permanent herds generally consisting of a single male and a band of females, with the remaining males forming small "bachelor" herds. The remaining species have temporary herds, lasting only a few months, which may be either single-sexed or mixed. In either case, there are clear hierarchies established amongst the individuals, usually with a dominant female controlling access to food and water resources and the lead male controlling mating opportunities.
Females, usually called mares
in horses and zebras, or, in the case of asses and donkeys, jennies, usually bear a single foal
, after a gestation period of approximately 11 months. Young equines are able to walk within an hour of birth, and are weaned
after four to thirteen months (animals living in the wild naturally wean foals at a later date than those under domestication
). Depending on species, living conditions and other factors, females in the wild may give birth every year or every other year.
Equines who are not in foal generally have a seasonal estrous cycle
, from early spring into autumn. Most females enter an anestrus period during the winter and thus do not cycle in this period. The reproductive cycle is controlled by the photoperiod (length of the day), with estrus triggered when the days begin to lengthen. Anestrus prevents the female from conceiving in the winter months, as that would result in her foaling during the harshest part of the year, a time when it would be more difficult for the foal to survive. However, equines who live near the equator
, where there is less change in length of day from season to season, have no anestrus period, at least in theory. Further, for reasons that are not clear, about twenty percent of domestic mares in the Northern Hemisphere will cycle the year round.
(in addition to Equus, the family includes approximately 35 other genera, all extinct)
, though the ensuing offspring are usually infertile. Hybrids include:
Any equine with partial zebra ancestry is called a zebroid
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of animals in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Equidae
Equidae
Equidae is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils. All extant species are in the genus Equus...
that includes horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s, donkey
Donkey
The donkey or ass, Equus africanus asinus, is a domesticated member of the Equidae or horse family. The wild ancestor of the donkey is the African Wild Ass, E...
s, and zebra
Zebra
Zebras are several species of African equids united by their distinctive black and white stripes. Their stripes come in different patterns unique to each individual. They are generally social animals that live in small harems to large herds...
s. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
known only from fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s. This article deals primarily with the extant species.
The term equine refers to any member of this genus, including any horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
. The word comes from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
equus, "horse", cognate with Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
"ἴκκος" (ikkos), "horse" (the earliest form of the word is the Mycenaean Greek i-qo, written in Linear B
Linear B
Linear B is a syllabic script that was used for writing Mycenaean Greek, an early form of Greek. It pre-dated the Greek alphabet by several centuries and seems to have died out with the fall of Mycenaean civilization...
syllabic script).
Characteristics
Equines are medium to large mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, with long heads, and necks with a mane
Mane (horse)
The mane is the hair that grows from the top of the neck of a horse or other equine, reaching from the poll to the withers, and includes the forelock or foretop. It is thicker and coarser than the rest of the horse's coat, and naturally grows to roughly cover the neck...
. Their legs are slender and end in a single, unguligrade toe, protected by a horny hoof
Horse hoof
A horse hoof is a structure surrounding the distal phalanx of the 3rd digit of each of the four limbs of Equus species, which is covered by complex soft tissue and keratinised structures...
. They have long, slender, tails, either ending in a tuft, or entirely covered in flowing hair. They are adapted to generally open terrain, from plain
Plain
In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or...
s and savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
s, to mountains or desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
s.
Binocular vision
Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
. Equines also have a vomeronasal organ
Vomeronasal organ
The vomeronasal organ , or Jacobson's organ, is an auxiliary olfactory sense organ that is found in many animals. It was discovered by Frederik Ruysch and later by Ludwig Jacobson in 1813....
, that allows males to use the flehmen, or 'lip-curling' response to assess the sexual state of potential mates. Equines are one of only two mammals (the other is the human) capable of producing copious sweat perspiration for thermoregulatory cooling, enabling fast running over long distances.
Equines are herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s, and feed predominantly on tough, fibrous food, such as grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es and sedges. When in need, they will also eat other vegetable matter, such as leaves, fruits, or bark, but are normally grazers, not browsers. Unlike ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s, with their complex stomachs, equines break down cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
in the "hindgut" or caecum, a part of the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
. Their dentition is almost complete, with cutting incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s to crop food, and grinding molars set well back behind a diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
. The dental formula for equines is:
Females, usually called mares
Mare (horse)
A mare is an adult female horse or other equine.In most cases, a mare is a female horse over the age of three, and a filly is a female horse age three and younger. However, in Thoroughbred horse racing, a mare is defined as a female horse more than four years old; in harness racing a mare is a...
in horses and zebras, or, in the case of asses and donkeys, jennies, usually bear a single foal
Foal
A foal is an equine, particularly a horse, that is one year old or younger. More specific terms are colt for a male foal and filly for a female foal, but these terms are used until the horse is age three or four. When the foal is nursing from its dam , it may also be called a suckling...
, after a gestation period of approximately 11 months. Young equines are able to walk within an hour of birth, and are weaned
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
after four to thirteen months (animals living in the wild naturally wean foals at a later date than those under domestication
Domestication
Domestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...
). Depending on species, living conditions and other factors, females in the wild may give birth every year or every other year.
Equines who are not in foal generally have a seasonal estrous cycle
Estrous cycle
The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies...
, from early spring into autumn. Most females enter an anestrus period during the winter and thus do not cycle in this period. The reproductive cycle is controlled by the photoperiod (length of the day), with estrus triggered when the days begin to lengthen. Anestrus prevents the female from conceiving in the winter months, as that would result in her foaling during the harshest part of the year, a time when it would be more difficult for the foal to survive. However, equines who live near the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
, where there is less change in length of day from season to season, have no anestrus period, at least in theory. Further, for reasons that are not clear, about twenty percent of domestic mares in the Northern Hemisphere will cycle the year round.
Classification
Family EquidaeEquidae
Equidae is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils. All extant species are in the genus Equus...
(in addition to Equus, the family includes approximately 35 other genera, all extinct)
- Genus Equus
- Subgenus Equus
- Equus ferus Wild horseWild HorseThe wild horse is a species of the genus Equus, which includes as subspecies the domesticated horse as well as the undomesticated Tarpan and Przewalski's Horse. The Tarpan became extinct in the 19th century, and Przewalski's Horse was saved from the brink of extinction and reintroduced...
- Equus ferus caballus Domestic horseHorseThe horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
- †Equus ferus ferus TarpanTarpanTarpan is an extinct subspecies of wild horse. The last individual of this subspecies died in captivity in Russia in 1909....
(historically extinct) - Equus ferus przewalskii Przewalski's HorsePrzewalski's HorsePrzewalski's Horse or Dzungarian Horse, is a rare and endangered subspecies of wild horse native to the steppes of central Asia, specifically China and Mongolia.At one time extinct in the wild, it has been reintroduced to its native habitat in Mongolia at the Khustain Nuruu...
or Mongolian Wild Horse or takhi - †Equus algericus (Pleistocene of Algeria)
- † North American caballid horses (Pleistocene; most likely synonymous with E. ferus):
- †Equus lambei Yukon Wild Ass (or Yukon Wild Horse)
- †Equus niobrarensis
- Subgenus †Amerhippus Hoffstetter, 1950 (jr synonym subgenus Tomolabis Cope, 1892) (this subgenus and the species therin are possibly synonymous with E. ferus)
- †Equus andium
- †Equus neogeus
- †Equus fraternus Leidy, 1860 (North America)
- †Equus santaeelenae
- †Equus scottiEquus scottiEquus scotti is an extinct species of Equus, the genus that includes the horse. E. scotti was native to North America and likely evolved from earlier, more zebra-like North American equids early in the Pleistocene Epoch...
Owen - †Equus niobrarensis
- †Equus conversidensEquus conversidensEquus conversidens Owen 1869, or the Mexican Horse, was a Pleistocene species of horse, now extinct, that inhabited North America.Fossils found in Mexico, Texas, Arizona, New Mexico, Oklahoma, Kansas and Florida have been identified as Equus conversidens...
Owen, 1863 ("Mexican Horse") (North America)
- Equus ferus caballus Domestic horse
- †New World stilt-legged horse (all following species within the group may be synonyms or regional races of a single species)
- †Equus francisciEquus francisciEquus francisci is an extinct species of Equus which was native to North America. Specimens of E. francisci have been found from northern Texas to southern South Dakota and in Alberta, Canada. Evidence shows this species to have evolved in North America.The species Equus francisci was...
Hay, 1915 - †Equus semiplicatus Cope, 1893 (North America)
- †Equus francisci
- Equus ferus Wild horse
- Subgenus AsinusAsinusThe subgenus Asinus encompasses four species and several subspecies of Equidae characterized by long ears, a lean, straight-backed build, a scant tail, and a reputation for considerable toughness and endurance....
- Equus africanus African Wild AssAfrican Wild AssThe African Wild Ass is a wild member of the horse family, Equidae. This species is believed to be the ancestor of the domestic donkey which is usually placed within the same species. They live in the deserts and other arid areas of northeastern Africa, in Eritrea, Ethiopia and Somalia; it...
- Equus africanus africanus Nubian Wild AssNubian Wild AssThe Nubian Wild Ass is a subspecies of the African wild ass, and probably the ancestor of domestic donkeys, since both have a stripe across the shoulder. The ass was domesticated about 6,000 years ago, probably in Egypt or Mesopotamia.The Nubian wild ass is most likely extinct in the wild since...
- Equus africanus asinus Domestic DonkeyDonkeyThe donkey or ass, Equus africanus asinus, is a domesticated member of the Equidae or horse family. The wild ancestor of the donkey is the African Wild Ass, E...
, Ass or Burro - †Equus africanus atlanticus Atlas Wild AssAtlas Wild AssThe Atlas Wild Ass , also known as Algerian Wild Ass is an extinct animal. It was last shown in a villa mural in AD 300 in Bona, Algeria, and went extinct after Roman sport hunting.-Taxonomy:...
- Equus africanus somalicus Somali Wild AssSomali Wild AssThe Somali Wild Ass is a subspecies of the African wild ass. It was found in the Southern Red Sea region of Eritrea, the Afar Region of Ethiopia, and Somalia...
- Equus africanus africanus Nubian Wild Ass
- Equus hemionus OnagerOnagerThe Onager is a large member of the genus Equus of the family Equidae native to the deserts of Syria, Iran, Pakistan, India, Israel and Tibet...
or Asiatic Ass- Equus hemionus hemionus Mongolian Wild AssMongolian Wild AssThe Mongolian Wild Ass is a subspecies of the Onager. It may be synonymous with the Gobi Kulan, Chigetai or Dziggetai...
, Dziggetai or Gobi Kulan - †Equus hemionus hemippus Syrian Wild AssSyrian Wild AssThe Syrian Wild Ass is an extinct subspecies of Equus hemionus that ranged across Syria, Jordan and Iraq.The Syrian Wild Ass was the smallest form of Equidae and could not be domesticated...
- Equus hemionus khur Indian Wild AssIndian Wild AssThe Indian wild ass also called khur, is a subspecies of the Onager native to Southern Asia.-Description:The Indian wild ass, as with most other Asian wild ass subspecies, is quite different from the African species. The coat is usually sandy, but varies from reddish grey, fawn, to pale chestnut...
or Khur - Equus hemionus kulan Turkmenian Kulan
- Equus hemionus onager Persian Onager
- Equus hemionus hemionus Mongolian Wild Ass
- Equus kiang KiangKiangThe kiang is the largest of the wild asses. It is native to the Tibetan Plateau, where it inhabits montane and alpine grasslands. Its current range is restricted to Ladakh in Jammu and Kashmir, plains of the Tibetan plateau and northern Nepal along the Tibetan border...
- Equus kiang chu Northern KiangNorthern KiangNorthern Kiang, Equus kiang chu, is a subspecies of the kiang. The Northern Kiang has a distinct "mating call". The Northern Kiang usually has a black stripe around the back of its head, which also separates it from the other subspecies of the kiang. Unlike the Southern Western and Eastern kiangs,...
- Equus kiang kiang Western KiangWestern KiangWestern Kiang, Equus kiang kiang, is a subspecies of the kiang. It is the first subspecies to be described....
- Equus kiang holdereri Eastern KiangEastern KiangEastern Kiang, Equus kiang holdereri, is a subspecies of kiang.The Eastern Kiang is the largest subspecies of the kiang....
- Equus kiang polyodon Southern KiangSouthern KiangSouthern Kiang, Equus kiang polyodon, is the smallest subspecies of kiang....
- Equus kiang chu Northern Kiang
- †Equus hydruntinus European AssEuropean AssThe European Ass is an extinct equine from the middle and late Pleistocene of Eurasia. It appeared first in the fossil report 300,000 years before present and did not disappear until Holocene times...
(late Paleolithic of southern Europe) - †Equus altidens (middle Pleistocene of Tadjikistan)
- †Equus tabeti (early middle Pleistocene of Algeria, known only from teeth and limb bones)
- †Equus melkiensis (late Paleolithic of Algeria, based on teeth and limb bones)
- †Equus graziosii (late Pleistocene of Italy)
- Equus africanus African Wild Ass
- Subgenus DolichohippusGrevy's ZebraThe Grévy's zebra , also known as the Imperial zebra, is the largest extant wild equid and one of three species of zebra, the other two being the plains zebra and the mountain zebra. Named after Jules Grévy, it is the sole extant member of the subgenus Dolichohippus. The Grévy's zebra is found in...
- Equus grevyi Grevy's ZebraGrevy's ZebraThe Grévy's zebra , also known as the Imperial zebra, is the largest extant wild equid and one of three species of zebra, the other two being the plains zebra and the mountain zebra. Named after Jules Grévy, it is the sole extant member of the subgenus Dolichohippus. The Grévy's zebra is found in...
- †Equus koobiforensis Eisenmann, 1983 (East Africa, ~2 million years (late Pliocene), similar but more derived than E.simplicidens and E.sanmeniensis
- †Equus oldowayensis Hopwood, 1937 (East Africa, late Pleiocene, early Pleistocene, likely conspecific with E.koobiforensis
- Equus grevyi Grevy's Zebra
- Subgenus HippotigrisZebraZebras are several species of African equids united by their distinctive black and white stripes. Their stripes come in different patterns unique to each individual. They are generally social animals that live in small harems to large herds...
- Equus quagga Plains ZebraPlains ZebraThe plains zebra , also known as the common zebra or Burchell's zebra, is the most common and geographically widespread species of zebra. It ranges from the south of Ethiopia through East Africa to as far south as Angola and eastern South Africa...
- Equus quagga boehmi Grant's ZebraGrant's ZebraThe Grant's Zebra is the smallest of six subspecies of the Plains Zebra.-Distribution:The distribution of this subspecies is in Zambia west of the Luangwa river and west to Kariba, Shaba Province of the Democratic Republic of the Congo, north to the Kibanzao Plateau. In Tanzania north from...
- Equus quagga borensis Selous' zebraSelous' ZebraThe Selous' Zebra, is one of the six subspecies of the Plains Zebra, spread over southeastern Africa. It is spread mostly in Mozambique, but nowadays it is endangered...
- Equus quagga chapmani Chapman's ZebraChapman's ZebraChapman's Zebra is a subspecies of Plains Zebra.They, like their relatives, are native to the savannah of north-east South Africa, north to Zimbabwe, west into Botswana, the Caprivi Strip in Namibia, and southern Angola. The Chapman's zebra eats mainly grass and occasionally shrubs...
- Equus quagga crawshayi Crawshay's ZebraCrawshay's ZebraThe Crawshay's zebra is a subspecies of the plains zebra. It is native to eastern Zambia, Malawi, and northern Mozambique. Crawshay's zebras can be distinguished from other subspecies of plains zebras in that its lower incisors lack an infundibulum....
- Equus quagga burchellii Burchell's ZebraBurchell's ZebraBurchell's Zebra is a southern subspecies of the Plains Zebra.-Range:Formerly Burchell's zebra ranged north of the Vaal/Orange river system, extending northwest via southern Botswana to Etosha and the Kaokoveld, southeast to Swaziland and Kwazulu-Natal...
- †Equus quagga quagga Gmelin, 1788 QuaggaQuaggaThe quagga is an extinct subspecies of the plains zebra, which was once found in great numbers in South Africa's Cape Province and the southern part of the Orange Free State. It was distinguished from other zebras by having the usual vivid marks on the front part of the body only...
(South Africa, extinction in early 20th century)
- Equus quagga boehmi Grant's Zebra
- Equus zebra L.,1758 Mountain ZebraMountain ZebraThe Mountain Zebra, Equus zebra, is a threatened species of equid native to south-western Angola, Namibia and South Africa. It has two subspecies, the Cape Mountain Zebra and Hartmann's Mountain Zebra , though it has been suggested these should be considered separate species.-Taxonomy:In 2004,...
- Equus zebra hartmannae Hartmann's Mountain ZebraHartmann's Mountain ZebraHartmann's mountain zebra, Equus zebra hartmannae, is a subspecies of the mountain zebra found in far south-western Angola and western Namibia.Hartmann's mountain zebras prefer to live in small groups of 7-12 individuals...
- Equus zebra zebra Cape Mountain ZebraCape Mountain ZebraCape mountain zebra, Equus zebra zebra, is a subspecies of the Mountain zebra found in the Western and Eastern Cape in South Africa. They mainly eat grass but if little food is left they will eat bushes...
- Equus zebra hartmannae Hartmann's Mountain Zebra
- †Equus mauritanicus Pomel, 1897 (Pleistocene transitional form between E. (Dolichohippus) and E. (Hippotigris), possibly via E.koobiforensis)
- Equus quagga Plains Zebra
- Subgenus †Parastylidequus
- †Equus parastylidens Mooser’s Horse
- incertae sedisIncertae sedis, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
- †Equus simplicidens Hagerman HorseHagerman HorseThe Hagerman horse , also called the Hagerman zebra or the American zebra, was a North American species of equid from the Pliocene period and the Pleistocene period. It was one of the oldest horses of the genus Equus. Discovered in 1928 in Hagerman, Idaho, it is believed to have been like the...
(North American Pleiocene - earliest known species of genus Equus) (perhaps closest to Dolichohippus) - †Equus cumminsii Cope, 1893 (North America; based on a single, 3 million year old tooth)
- †Equus livenzovensis Baihusheva, 1978 (southern Russia and western Europe, Pleiocene - highly similar to E. simplicidens
- †Equus sanmeniensis Teilhard&Piveteau, 1930 (south China, late? Pliocene; similar but more derived than E.livenzovensis
- †Equus teilhardi Eisenmann, 1975 (south China, late(?) Pliocene; similar to E.sanmeniensis but smaller, likely synonym)
- †Equus numidicus Pomel, 1897
- †Equus plicidens Owen, 1844 (late Pliocene, only teeth known)
- †Equus stenonis group
- †Equus stenonis Cocchi, 1867 (Europe to China, late Pleiocene)
- †Equus stenonis vireti (late Pliocene)
- †Equus stenonis senezensis (late Pliocene)
- †Equus stenonis guthi (late Pliocene, France)
- †Equus stenonis pamirensis (=Hippotigris pamirensis) (late Pliocene, central Asia)
- †Equus sivalensisEquus sivalensisEquus sivalensis is an extinct equid, discovered in the Siwalik hills of Pakistan. Remains date to 2.6 million years ago, and it is assumed that it was extinct during the last Ice Age, between 75,000 and 10,000 years ago, as part of the late Pleistocene megafaunal extinction...
(late Pleiocene (?), India; similar to E.stenonis in skull shape) - †Equus stehlini (early Pleistocene, ~1 million years ago; similar but smaller than E. stenonis
- †Equus bressanus (early Pleistocene, ~1 million years ago; similar but much larger than E. stenonis
- †Equus sussenbornensis Wüst, 1901 (early middle Pleistocene of Europe)
- †Equus verae Sher, 1971 (middle Pleistocene of north eastern Asia)
- †Equus namadicusEquus namadicusEquus namadicus is a prehistoric equid, known from equid remains dating to the Pleistocene excavated in deposits of the Narmada river, in India. It is contemporary and possibly even identical to, Equus sivalensis.-References:...
(middle paleolithic sites in India)
- †Equus stenonis Cocchi, 1867 (Europe to China, late Pleiocene)
- †subgenus Allozebra & Hesperohippus (N. American lineage of middle to late Pleistocene)
- †Equus idahoensis
- †Equus (A.) occidentalis
- †Equus (A.) excelsus
- †Equus (H.) pacificus
- †Equus complicatus
- †Equus fraternus
- Equus major Boule (nomen dubium)
- †Equus giganteus group
- †Equus giganteus
- †Equus pectinatus
- †Equus crinidens
- †Equus simplicidens Hagerman Horse
- Subgenus Equus
Cross-breeds
Different species of Equus can crossbreedCrossbreed
A crossbreed or crossbred usually refers to an animal with purebred parents of two different breeds, varieties, or populations. Crossbreeding refers to the process of breeding such an animal, often with the intention to create offspring that share the traits of both parent lineages, or producing...
, though the ensuing offspring are usually infertile. Hybrids include:
- MuleMuleA mule is the offspring of a male donkey and a female horse. Horses and donkeys are different species, with different numbers of chromosomes. Of the two F1 hybrids between these two species, a mule is easier to obtain than a hinny...
, a cross between a male donkeyDonkeyThe donkey or ass, Equus africanus asinus, is a domesticated member of the Equidae or horse family. The wild ancestor of the donkey is the African Wild Ass, E...
and a female horseHorseThe horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
. Mules are the most common type of hybrid equine and are renowned for their toughness, surefootedness, and working ability. - HinnyHinnyA hinny is a domestic equine hybrid that is the offspring of a male horse and a female donkey . It is similar to the more common mule, which is the product of a female horse and a male donkey....
, a cross between a female donkeyDonkeyThe donkey or ass, Equus africanus asinus, is a domesticated member of the Equidae or horse family. The wild ancestor of the donkey is the African Wild Ass, E...
and a male horseHorseThe horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
. Considered a less desirable cross than a mule, generally smaller in size and not as hardy.
Any equine with partial zebra ancestry is called a zebroid
Zebroid
A zebroid is the offspring of any cross between a zebra and any other equine: essentially, a zebra hybrid. In most cases, the sire is a zebra stallion. Offspring of a donkey sire and zebra dam, called a zebra hinny, or donkra, do exist but are rare. Zebroids have been bred since the 19th century...
.
Sources
- Burke, et al. 2003. The systematic position of Equus hydruntinus, an extinct species of Pleistocene equid. Quaternary Research 59(3):459-469.
- Duncan, P. (ed.). 1992. Zebras, Asses, and Horses: an Action Plan for the Conservation of Wild Equids. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland.
- Equid Specialist Group 1996. Equus ferus. In: IUCN 2004. 2004 IUCN Red List of Threatened Species.
. Downloaded on 21 January 2006. - Equid Specialist Group 1996. Equus ferus ssp. przewalskii. In: IUCN 2004. 2004 IUCN Red List of Threatened Species.
. Downloaded on 21 January 2006. - International Commission on Zoological Nomenclature. 2003. Opinion 2027 (Case 3010). Usage of 17 specific names based on wild species which are pre-dated by or contemporary with those based on domestic animals (Lepidoptera, Osteichthyes, Mammalia): conserved. Bull.Zool.Nomencl., 60:81-84.
- Moehlman, P.D. 2002. Equids. Zebras, Assess and Horses. Status Survey and Conservation Action Plan. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland. (http://www.iucn.org/themes/ssc/publications/actionplans.htm#Equids2002)