Hippidion
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 two million and 11,000 years ago. They were one of two lineages of equines native to South America during the Pleistocene epoch alongside those of the Equus subgenus Amerhippus.
Hippidion has been considered a descendant of pliohippines,[1] equines that migrated into the South American continent around 2.5 million years ago.[1][2] 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.[1][2] However this was later shown to be incorrect, with more complete sequences finding Hippidion as an outgroup to all living equines[3] and less closely related to living equines than the "New World stilt legged horse", Haringtonhippus francisci.[4]
Hippidion is traditionally thought to have 3 species, H. principale, H. saldiasi and H. devillei, however, in the 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.[3]
Hippidion and other South American equines became extinct approximately 8,000 years ago.[5] Specific archaeological recovery at the Cueva del Milodon site in Patagonian Chile demonstrates that Hippidion saldiasi existed in that vicinity in the era of 10,000 to 12,000 years before present, making it the last surviving member of its species.[6] Equines did not reappear in South America until the 16th century, as a result of introduction by humans.
It stood approximately 1.4 metres (4.6 ft) (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.[7]
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.[7]
