Equus neogeus is an extinct species ofequine native to South America during thePleistocene. It was formerly thought to be several distinct species within the subgenusAmerhippus, but was later shown to be a single morphologically variable species. It is thought to be closely related to true horses.
While they have formerly been referred to as belonging to 5 separate species, this has been revised down into three,[1] and more recently a single, morphologically variable speciesEquus neogeus.[2][3] Some authors continue to recognise three species, restrictingEquus neogeus to large-sized individuals spanning from thePampas toNortheast Brazil, while separating the smallerEquus andium for populations in the northern-central Andes, andEquus insulatus for medium-sized animals spanning from Bolivia to Venezuela. These authors suggest thatE. insulatus was the ancestor of the other species.[4] Historically, South AmericanEquus species were placed in the subgenusAmerhippus, but this has subsequently been questioned.[4] A 2008 study ofmitochondrial DNA fragments of a specimen ofE. neogeus found it to be nested within mitochondrial lineages ofE. caballus,[5] however, later studies suggested that this result required more specimens to be analysed for confirmation.[6] A close relationship to caballine horses was also supported by a 2019 morphological analysis study.[7]
A 2019 study suggested thatEquus neogeus specimens from Uruguay were primarilygrazers that fed on bothC4 andC3 grasses inprairies and open woodlands.[12]
Equus neogeus became extinct at the end of the Late Pleistocene as part of theend-Pleistocene extinctions, along with the vast majority of other large mammals in South America.[13] The youngest remains date to approximately 11,700 yearsBefore Present (BP), in Río Quequén Salado, in the southwest ofBuenos Aires province, Argentina.[11] The extinctions followed human arrival to the Americas, and several sites show evidence of human interaction withEquus neogeus, which may have been a factor in its extinction.[14] At the Paso Otero 5 site in the Pampas of northeast Argentina,Fishtail points are associated with burned bones ofEquus neogeus and other extinct megafauna. The bones appear to have been deliberately burned as a source of fuel. Due to the poor preservation of the bones there is no clear evidence of human modification.[15] At the Taguatagua 3 in central Chile, dating to around 12,440–12,550 years BP, a firstphalanx ofEquus was found near a hearth, alongside the remains of other megafauna, including the much more abundant remains ofgomphotheres (elephant relatives).[16] At the Arroyo Seco 2 site in the Argentinian Pampas, which has multiple episodes of human activity dating to between 14,782 and 11,142 cal yr BP remains ofEquus neogeus (alongside those of other megafauna) are associated with human artifacts and exhibit fracture marks indicative of butchery.[14][17]
^abPrado, J. L.; Alberdi, M. A. T.; De Reyes, M. N. L.; Poiré, D. G.; Canalicchio, J. M. (2013). "New material ofEquus (Amerhippus)neogeus (Mammalia, Perissodactyla) from the late Pleistocene of Olavarría (Argentina)".Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen.269 (2): 125.Bibcode:2013NJGPA.269..125P.doi:10.1127/0077-7749/2013/0340.hdl:10261/115119.
