''Equus neogeus'' is an extinct species of
equine
Equinae is a subfamily of the family Equidae, known from the Hemingfordian stage of the Early Miocene (16 million years ago) onwards. They originated in North America, before dispersing to every continent except Australia and Antarctica. They are ...
native to South America during the
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
. It was formerly thought to be several distinct species within the subgenus ''Amerhippus'', but was later shown to be a single morphologically variable species. It is thought to be closely related to true horses.
Taxonomy
While they have formerly been referred to as belonging to 5 separate species, this has been revised down into three, and more recently a single, morphologically variable species ''Equus neogeus''. Some authors continue to recognise three species, restricting ''Equus neogeus'' to large-sized individuals spanning from the
Pampas
The Pampas (; from Quechua 'plain'), also known as the Pampas Plain, are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all o ...
to
Northeast Brazil
The Northeast Region of Brazil ( ) is one of the five official and political regions of Brazil, regions of the country according to the Brazilian Institute of Geography and Statistics. Of Brazil's twenty-six states, it comprises nine: Maranhão, ...
, while separating the smaller ''Equus andium'' for populations in the northern-central Andes, and ''Equus insulatus'' for medium-sized animals spanning from Bolivia to Venezuela. These authors suggest that ''E. insulatus'' was the ancestor of the other species.
Historically, South American ''Equus'' species were placed in the subgenus ''Amerhippus'', but this has subsequently been questioned.
A 2008 study of
mitochondrial DNA
Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...
fragments of a specimen of ''E. neogeus'' found it to be nested within mitochondrial lineages of ''
E. caballus,'' however, later studies suggested that this result required more specimens to be analysed for confirmation. A close relationship to caballine horses was also supported by a 2019 morphological analysis study.
Description

''Equus neogeus'' measured roughly tall and weighed approximately .
Distribution
They were one of two groups of equines in South America, alongside ''
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 2.5 million and 11,000 years ago. They were one of two lineages of eq ...
''.
Fossils have been recovered from the
Tarija Formation of
Bolivia
Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...
, the
Serranía del Perijá
The Serranía del Perijá, Cordillera de Perijá or Sierra de Perijá is a mountain range, an extension of the eastern Andean branch ( Cordillera Oriental), in northern South America, between Colombia and Venezuela, ending further north in the ...
in
Venezuela
Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...
, the
Chiu-Chiu Formation of
Chile
Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
, the
Sabana Formation of the
Bogotá savanna
The Bogotá savanna is a savanna#Savanna ecoregions, montane savanna, located in the southwestern part of the Altiplano Cundiboyacense in the center of Colombia. The Bogotá savanna has an extent of and an average altitude of . The savanna is si ...
in
Colombia
Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
,
and from various locations in
Ecuador
Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...
.
''Equus'' first appeared in South America during the late
Early Pleistocene
The Early Pleistocene is an unofficial epoch (geology), sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently esti ...
-earliest
Middle Pleistocene
The Chibanian, more widely known as the Middle Pleistocene (its previous informal name), is an Age (geology), age in the international geologic timescale or a Stage (stratigraphy), stage in chronostratigraphy, being a division of the Pleistocen ...
, around 1 million to 800,000 years ago, based on remains found near
Tarija, Bolivia.
Paleobiology
A 2019 study suggested that ''Equus neogeus'' specimens from Uruguay were primarily
grazers that fed on both
C4 and
C3 grasses in
prairie
Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...
s and open woodlands.
Extinction
''Equus neogeus'' became extinct at the end of the Late Pleistocene as part of the
end-Pleistocene extinctions, along with the vast majority of other large mammals in South America.
The youngest remains date to approximately 11,700 years
Before Present
Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...
(BP), in Río Quequén Salado, in the southwest of
Buenos Aires
Buenos Aires, controlled by the government of the Autonomous City of Buenos Aires, is the Capital city, capital and largest city of Argentina. It is located on the southwest of the Río de la Plata. Buenos Aires is classified as an Alpha− glob ...
province, Argentina.
The extinctions followed human arrival to the Americas, and several sites show evidence of human interaction with ''Equus neogeus,'' which may have been a factor in its extinction.
At the Paso Otero 5 site in the Pampas of northeast Argentina,
Fishtail points are associated with burned bones of ''Equus 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. At the Taguatagua 3 in central Chile, dating to around 12,440–12,550 years BP, a first
phalanx
The phalanx (: phalanxes or phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar polearms tightly packed together. The term is particularly used t ...
of ''Equus'' was found near a hearth, alongside the remains of other megafuna, including the much more abundant remains of
gomphothere
Gomphotheres are an extinct group of proboscideans related to modern elephants. First appearing in Africa during the Oligocene, they dispersed into Eurasia and North America during the Miocene and arrived in South America during the Pleistocene a ...
s (elephant relatives). 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 of ''Equus neogeus'' (alongside those of other megafauna) are associated with human artifacts and exhibit fracture marks indicative of butchery.
References
{{Equus
Pleistocene horses
Pleistocene mammals of South America
Lujanian
Ensenadan
Uquian
Pleistocene Bolivia
Fossils of Bolivia
Pleistocene Chile
Fossils of Chile
Pleistocene Colombia
Fossils of Colombia
Pleistocene Ecuador
Fossils of Ecuador
Pleistocene Venezuela
Fossils of Venezuela
Fossil taxa described in 1950
Taxa named by Robert Hoffstetter
Animal subgenera
Equus (genus)
Pleistocene Argentina