Hippidion (meaning little horse) is an extinct genus of equine that lived in South America from the Late Pliocene to the end of the Late Pleistocene (Lujanian), between 2.5 million and 11,000 years ago. They were one of two lineages of equines native to South America during the Pleistocene epoch, alongside Equus (Amerhippus) neogeus.
Hippidion has been considered a descendant of pliohippines, equines that migrated into the South American continent around 2.5 million years ago. Early analysis of the ancient DNA of Hippidion and other New World Pleistocene equines supported the novel hypothesis that Hippidion was actually a member of the living genus Equus, with a particularly close relationship to the wild horse, Equus ferus. However this was later shown to be incorrect, with more complete sequences finding Hippidion as an outgroup to all living equines and less closely related to living equines than the "New World stilt legged horse", Haringtonhippus francisci.
Hippidion is traditionally thought to have 3 species, H. principale, H. saldiasi and H. devillei, however, in a 2015 DNA analysis, the single sampled H. principale specimen was found to be nested with H. saldiasi, with H. devillei found to be clearly genetically distinct.
It stood approximately (also 13.2 hh) high at the shoulders and resembled a donkey. The skull of Hippidion is noted for its nasal bone, which projects forward from the skull.
A study found that Late Pleistocene specimens of Hippidion had lower δ13C values than those of specimens of Amerhippus, indicating a preference for C3 woodland and wooded open habitats. H. principale is suggested to have been a mixed feeder (both browsing and grazing), as opposed to the grazing diet of the contemporary Equus neogeus.
Remains of Hippidion saldiasi have been recovered in locations such as the Piedra Museo site, Santa Cruz, Argentina and Cueva del Milodon, Chile. The significance of such archaeological recovery is amplified by the association with hunting of these animals by prehistoric man at possible Pre-Clovis horizons.