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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 ?
An outbreak of glanders is ongoing in equids in Bahrain (6).
Requests to the US State Department and US military authorities resulted in release of attenuated VEE virus vaccine strain TC-83 for emergency use in equids to stop equine disease and interrupt human infections.
There is no evidence of butchering of the equid skeletons, in contrast to the abundant evidence for butchering on bovid and ovicaprid bones from Aissa Dugje and neighbouring sites.
Chapter 3, "The Donkey in Near Eastern Archaeology," presents most of the evidence available for equid burials, focusing, whenever possible, on donkey remains.
However, he wanted to expand the outreach effort by visiting other countries, speaking with more third-world equid doctors and starting a movement to inform veterinarians about the plight of the world's working equids, most of which work under terrible conditions but are vital to the family's survival in these countries.
Both sites have a particularly large sample of equids from both the Equini and Hipparionini tribes, common constituents in many medial to late Miocene assemblages.
Zoophilic dermatophytes spend their life on animal keratin and don't live on hair-baits in the soil (Simpanya 2000), such as Trichophyton equinum, which has a narrow range of receptive hosts mostly infecting equids.
Advances in the reconstruction of ungulate ecomorphology with application to early fossil equids.
Discussion of the nutrition and feeding of donkeys, mules, and captive equids is included.
Carbon isotopes, diets of North American equids, and the evolution of North American [C.
Allometric scaling in three sizes of equids (equus eaballus).