''Pliohippus'' (Greek (, "more") and (, "horse")) is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

Equidae Equidae (commonly known as the horse family) is the Taxonomy (biology), taxonomic Family (biology), family of Wild horse, horses and related animals, including Asinus, asses, zebra, zebras, and many extinct species known only from fossils. The fa ...

, the horse family. ''Pliohippus'' arose in the middle

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, around 15 million years ago. The long and slim limbs of ''Pliohippus'' reveal a quick-footed

steppe In physical geography, a steppe () is an ecoregion characterized by grassland plains without closed forests except near rivers and lakes. Steppe biomes may include: * the montane grasslands and shrublands biome * the tropical and subtropica ...

animal. While some specimens have one toe per leg, others have three (the main toe and two non-functional side toes). Until recently, because of its many anatomical similarities, ''Pliohippus'' was believed to be the ancestor of the present-day

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

and its relatives in '' Equus''. Although ''Pliohippus'' clearly is an

equid Equidae (commonly known as the horse family) is the Taxonomy (biology), taxonomic Family (biology), family of Wild horse, horses and related animals, including Asinus, asses, zebra, zebras, and many extinct species known only from fossils. The fa ...

and thus related to ''Equus'', its skull had deep facial ''fossae'', a feature not found in any member of ''Equus''. Additionally, its teeth were strongly curved, unlike the very straight teeth of modern horses. Consequently, it is unlikely to be the ancestor of the modern horse; instead, it is likely to be the ancestor of '' Astrohippus''.MacFadden, B. J. (1984). "Astrohippus and Dinohippus". ''J. Vert. Paleon''. 4(2):273-283. ''Pliohippus'' stood approximately 1.25 metres, similar to the modern horse. Also like the modern horse, ''Pliohippus'' was a grazer that fed on steppe grasses of the North American plains it inhabited. Fossils of ''Pliohippus'' have been found at many late Miocene localities in Colorado, the Great Plains (Nebraska, including Ashfall Fossil Beds and the Dakotas) and also Canada. ''Pliohippus'' has been found beside '' Neohipparion''. File:Pliohippus pernix Wikipedia Juandertal.jpg, Life reconstruction of ''P. pernix''

References

{{Taxonbar, from=Q612924 Miocene horses Pliocene horses Prehistoric placental genera Transitional fossils Neogene mammals of North America Barstovian Clarendonian Hemphillian Fossil taxa described in 1874 Taxa named by Othniel Charles Marsh Equini