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(vertebrate zoology)
A family of perissodactyl mammals in the superfamily Equoidea, including the horses, zebras, and donkeys.



a family of the order Perissodactyla. It comprises three subfamilies with approximately 20 genera, including extinct genera (such as Hyracotherium, Anchitherium, Mesohippus, Miohippus, Merychippus, Hipparion, and Pliohippus) and the only surviving genus, Equus.

The family comprises animals varying greatly in appearance and structure. With the exception of the most ancient (Eocene) representatives, equids are well-proportioned animals, with long legs and a very developed large third toe encased in a hoof; the second and fourth toes are greatly reduced (they are absent in modern equids). The facial part of the skull is greatly elongated. The cheek teeth are hypsodont and grow as they wear down. The equids evolved so as to adapt to fast running in open spaces and eating coarse vegetation. During the evolutionary process, the legs lengthened, the joints straightened, the middle toe enlarged, and the side toes gradually reduced. The face lengthened as the molars grew larger, and the premolars acquired a molar-like appearance and a complex folded chewing surface.

The history of the family Equidae has been well studied in North America, where they lived from the early Eocene epoch to the late Pliocene epoch. In the eastern hemisphere, in different geological periods there existed representatives of the family that were not linked to one another evolutionarily. The ancestors of the modern equids came to the eastern hemisphere from North America in the late Pliocene epoch, and in different parts of their vast area of distribution gave rise to different groups of modern equids. The history of the family’s development studied in detail by V. O. Kovalevskii is a classic example of research into the specific evolutionary paths of a large group of animals.


Kovalevskii, V. O. Sobranie nauchnykh trudov, vol. 2. Moscow, 1956.
Osnovy paleontologii: Mlekopitaiushchie. Moscow, 1962.
Simpson, G. G. Horses. New York, 1951.


References in periodicals archive ?
Using such data may not only enhance our general understanding of life-history trade-offs, but also breeding protocols and thus offspring production aiding reintroduction or conservation projects for these highly endangered equids (Nowak 1999, Bahloul et al.
2008: Resource selection by sympatric wild equids in the Mongolian Gobi.
Actually, while treating the topic of donkeys, the author also deals with other equids, such as onagers, horses, and hybrids.
Merriam's vision, passion and dedication to thousands of working equids and their families.
A comparison of equid taxa from both sites would provide improved understanding of the relative age of the assemblage at the Mission Pit, and would provide unique insight into environmental variation within the northern Great Plains during the medial to late Miocene.
That this building was associated in some way with the breeding or trading of the hybrid kunga equids is attested by cuneiform documents recording the receipt or dispatch of these animals, found in courtyard 43 near the door of the temple antecella (Eidem et al.
38) In all Lemuel' s mulish and self-imposed hybridity, sensuality had appeared to retreat with the female Yahoo, but it seems that at least one reader had suspected a hidden desire (on Mary' s part if not on her husband's) that he might be hung like an equid.
The only equid in the area, plains zebra Equus burchelli bohmi, had to be omitted from our analysis as sex and age classes could not be determined unambiguously in the field.
Epidemiological investigation of equid herpesvirus-4 (EHV-4) excretion assessed by nasal swabs taken from thoroughbred foals.
1999): "Intertaxonomic variability in patterns of bone density and the differential representation of bovid, cervid and equid elements in the archaeological record", American Antiquity, 64, pp.
While it is far from mainstream, equine cloning has progressed steadily since the first equid clones were born in 2003 - three mule foals produced at the University of Idaho, and a horse foal born in the Laboratory of Reproductive Technology in Cremona, Italy.
A sampling of topics: metabolic responses of muscle to exercise, causal factors of equine stereotypy, development and application of modern breeding technologies to the horse, towards a common equine rationing system across the European Union, exploiting dietary fiber in equid diets, and the challenge of attracting and retaining sponsorship in eventing.