Instruct: Given a question, retrieve passages that can help answer the question.
Query: What other species belong to the Equidae?
Equidae (sometimes known as the horse family) 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. Equidae belongs to the order Perissodactyla, which includes the extant tapirs and rhinoceros, and several extinct families.
Donkeys can interbreed with other members of the family Equidae, and are commonly interbred with horses. The hybrid between a jack and a mare is a mule, valued as a working and riding animal in many countries. Some large donkey breeds such as the Asino di Martina Franca, the Baudet de Poitou and the Mammoth Jack are raised only for mule production. The hybrid between a stallion and a jenny is a hinny, and is less common. Like other inter-species hybrids, mules and hinnies are usually sterile. Donkeys can also breed with zebras in which the offspring is called a zonkey (among other names).
The mountain zebra ("Equus zebra") is a species in the family Equidae. It is native to south-western Angola, Namibia, and South Africa.
Equus is a genus of mammals in the family Equidae, which includes horses, donkeys, and zebras. Within Equidae, "Equus" is the only recognized extant genus, comprising seven living species. The term equine refers to any member of this genus, including horses. 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 (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.
The order includes about 17 species divided into three families: Equidae (horses, asses, and zebras), Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). 
"Dinohippus" was the most common species of Equidae in North America during the late Pliocene. It was originally thought to be monodactyl, but a 1981 fossil find in Nebraska shows some were tridactyl.
Hyracotherium ( ; "hyrax-like beast") is an extinct genus of very small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, dog-sized animal was once considered to be the earliest known member of Equidae before the type species, "H. leporinum", was reclassified as a palaeothere, a perissodactyl family basal 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".
Ancestral rhinoceroses first diverged from other perissodactyls in the Early Eocene. Mitochondrial DNA comparison suggests the ancestors of modern rhinos split from the ancestors of Equidae around 50 million years ago. The extant family, the Rhinocerotidae, first appeared in the Late Eocene in Eurasia, and the ancestors of the extant rhino species dispersed from Asia beginning in the Miocene.
Bequaert describes the extensive color and shape similarities between "B. lecheguana" and a number of other species with the word “homeochromic” instead of “mimic”. He lists a number of vespid wasps and potter wasps belonging to the genera "Pachodynerus", "Odynerus", and "Ancistrocerus", and several crabronid wasps of the genera "Gorytes" and "Cerceris". Along with wasps, there are several bee species that are homeochromic, including mason bees of the genera "Megachile", "Anthidiellum", "Hypanthidium", and "Dianthidium", Cuckoo bees belonging to the genus "Epeolus", stingless "Trigona" bees, and sweat bees from the genus "Halictus". He also lists a soldier fly of the genus "Stratiomys" as a homeochromic species. While it is unclear what species he is referring to, he cites "Stelis costaricensis" as a homeochromic species, and while "Stelis" is a genus of orchid, he did not elaborate enough to rule out the possibility that he was simply using an outdated name for another insect.
The horse family Equidae and the genus "Equus" evolved in North America, before the species moved into the Eastern Hemisphere. Studies using ancient DNA, as well as DNA of recent individuals, show the presence of two closely related horse species in North America, the wild horse and "Haringtonhippus francisci", the "New World stilt-legged horse"; the latter has been taxonomically assigned to various names.
Covering sickness, or dourine (French, from the Arabic "darina", meaning mangy (said of a female camel), feminine of "darin", meaning dirty), is a disease of horses and other members of the family Equidae. The disease is caused by "Trypanosoma equiperdum", which belongs to an important genus of parasitic protozoa, and is the only member of the genus that is spread through sexual intercourse. The occurrence of dourine is notifiable in the European Union under legislation from the OIE. There currently is no vaccine and although clinical signs can be treated, there is no cure.
The family became relatively diverse during the Miocene, with many new species appearing. By this time, equids were more truly horse-like, having developed the typical body shape of the modern animals.[2] Many of these species bore the main weight of their bodies on their central, third, toe, with the others becoming reduced, and barely touching the ground, if at all. The sole surviving genus, Equus, had evolved by the early Pleistocene, and spread rapidly through the world.[3]
Τrypanosoma equiperdum is a species of kinetoplastid parasites that causes Dourine or covering sickness in horses and other animals in the family equidae. "T. equiperdum" is the only trypanosome that is not spread by an insect vector. There has been substantial controversy surrounding whether "T. equiperdum" should be considered a unique species, or a strain of "T. evansi" or "T. brucei". "T. equiperdum" is unique in that its kinetoplast, the network of connected rings that make up its mitochondrial DNA, consists of thousands of "minicircles" that are identical in sequence.
Brontotheriidae, also called Titanotheriidae, is a family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs. Superficially, they looked rather like rhinos, although they were actually more closely related to horses; Equidae and Brontotheriidae make up the suborder Hippomorpha. They lived around 56–34 million years ago, until the very close of the Eocene.
Due to the relatively recent redefinition of the species, most published work does not yet distinguish between the new species belonging to the previously recognised "A. pullulans" species complex. It is therefore not clear to what extent this knowledge is valid for "A. pullulans" "s. str." and what should be attributed to the three new species.
Besides the horse, there are six other species of genus Equus in the Equidae family. These are the ass or donkey, Equus asinus; the mountain zebra, Equus zebra; plains zebra, Equus quagga; Grévy's zebra, Equus grevyi; the kiang, Equus kiang; and the onager, Equus hemionus.[142]
Another distinguishing characteristic of the bayou killifish also belongs to the subgenera that it belongs to, "Fundulus." All seven species belonging to this subgenera, including "F. pulvereus", are native to the Gulf coast and Atlantic waters of North America. What makes them different from other killifish species is the formation of the maxilla, a bone that helps form the upper jaw of the fish. In "F. pulvereus" and other species belonging to the subgenera "Fundulus", the maxilla has a distinctly concave edge near the back of the bone, toward the brain. In other species belonging to different subgenera, the maxilla may not be concave at all. Instead, they possess a straightened maxilla with no concavity towards the anterior. The purpose of the concavity in the maxilla of "F. pulvereus" is relatively unknown. However, if one were to study the morphology and skeletal structures of many different species of killifish carcasses, they would easily be able to pick out "F. pulvereus" because of their distinctive maxilla.
The onager is a member of the subgenus "Asinus", belonging to the genus "Equus" and is classified under the family Equidae. The species was described and given its binomial name "Equus hemionus" by German zoologist Peter Simon Pallas in 1775.
Order Perissodactyla (In addition to Equidae, Perissodactyla includes four species of tapir in a single genus, as well as five living species (belonging to four genera) of rhinoceros.) † indicates extinct taxa. Family Equidae Genus †Haringtonhippus[4] Genus †Epihippus Genus †Haplohippus Genus †Heptaconodon Genus †Eohippus Genus †Minippus Genus †Orohippus Genus †Pliolophus Genus †Protorohippus Genus †Sifrhippus Genus †Xenicohippus Genus †Eurohippus Genus †Propalaeotherium Subfamily †Anchitheriinae Genus †Anchitherium Genus †Archaeohippus Genus †Desmatippus Genus †Hypohippus Genus †Kalobatippus Genus †Megahippus Genus †Mesohippus Genus †Miohippus Genus †Parahippus Genus †Sinohippus Subfamily Equinae Genus †Merychippus Genus †Scaphohippus Genus †Acritohippus Tribe †Hipparionini Genus †Eurygnathohippus Genus †Hipparion Genus †Hippotherium Genus †Nannippus Genus †Neohipparion Genus †Proboscidipparion Genus †Pseudhipparion Tribe Equini Subtribe Protohippina Genus †Calippus Genus †Protohippus Genus †Astrohippus Genus †Dinohippus Genus Equus (22 species, 7 extant) Genus †Hippidion Genus †Onohippidium Genus †Pliohippus Genus †Heteropliohippus Genus †Parapliohippus
The oldest known fossils assigned to Equidae date from the early Eocene, 54 million years ago. They had been assigned to the genus "Hyracotherium", but the type species of that genus is now considered not a member of this family, but the other species have been split off into different genera. These early Equidae were fox-sized animals with three toes on the hind feet, and four on the front feet. They were herbivorous browsers on relatively soft plants, and already adapted for running. The complexity of their brains suggest that they already were alert and intelligent animals. Later species reduced the number of toes, and developed teeth more suited for grinding up grasses and other tough plant food.
The oldest known fossils assigned to Equidae date from the early Eocene, 54 million years ago. They used to be assigned to the genus Hyracotherium, but the type species of that genus now is regarded to be not a member of this family. The other species have been split off into different genera. These early Equidae were fox-sized animals with three toes on the hind feet, and four on the front feet. They were herbivorous browsers on relatively soft plants, and already adapted for running. The complexity of their brains suggest that they already were alert and intelligent animals.[1] Later species reduced the number of toes, and developed teeth more suited for grinding up grasses and other tough plant food.
Desmatippus is an extinct, three-toed, browsing member of the Equidae. It lived in what is now North America during the Miocene period (about 23 mya to 5 mya). "Desmatippus" was 60 cm height and 20 kg in weight.
For a span of about 20 million years, "Eohippus" thrived with few significant evolutionary changes. The most significant change was in the teeth, which began to adapt to its changing diet, as these early Equidae shifted from a mixed diet of fruits and foliage to one focused increasingly on browsing foods. During the Eocene, an "Eohippus" species (most likely "Eohippus angustidens") branched out into various new types of Equidae. Thousands of complete, fossilized skeletons of these animals have been found in the Eocene layers of North American strata, mainly in the Wind River basin in Wyoming. Similar fossils have also been discovered in Europe, such as "Propalaeotherium" (which is not considered ancestral to the modern horse).
Fructans also appear in grass, with dietary implications for horses and other grazing animals (Equidae).
Three lineages within Equidae are believed to be descended from the numerous varieties of "Merychippus": "Hipparion", "Protohippus" and "Pliohippus". The most different from "Merychippus" was "Hipparion", mainly in the structure of tooth enamel: in comparison with other Equidae, the inside, or tongue side, had a completely isolated parapet. A complete and well-preserved skeleton of the North American "Hipparion" shows an animal the size of a small pony. They were very slim, rather like antelopes, and were adapted to life on dry prairies. On its slim legs, "Hipparion" had three toes equipped with small hooves, but the side toes did not touch the ground.