Hipparionini is a tribe of three-toed horses in the subfamily
Equinae
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 ar ...
. They had body forms similar to modern equines, with high-crowned teeth. They first appeared in North America during the Early Miocene around 17 million years ago, before migrating into the
Old World
The "Old World" () is a term for Afro-Eurasia coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...
around 11.4-11.0 million years ago. The youngest species date to the
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 ...
, becoming extinct following the arrival of modern equines of the genus '' Equus'' to the Old World.
Description
Hipparionines varied widely in size, with the smallest species like ''Hipparion periafricanum'' having a body mass of only , considerably smaller than living equines, while the largest species had body masses over .
Evolutionary history
In North America, hipparionins were equally diverse to equins during the
Middle Miocene
The Middle Miocene is a sub-epoch of the Miocene epoch (geology), epoch made up of two Stage (stratigraphy), stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene.
The sub-epoch lasted from 15.97 ± 0. ...
but overtook them in
species richness
Species richness is the number of different species represented in an community (ecology), ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the Abundance (ecology), abunda ...
during the
Late Miocene
The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...
and
Early Pliocene
Early may refer to:
Places in the United States
* Early, Iowa, a city
* Early, Texas, a city
* Early Branch, a stream in Missouri
* Early County, Georgia
* Fort Early, Georgia, an early 19th century fort
Music
* Early B, stage name of Jamaican d ...
. At the end of the
Hemphillian
The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...
, hipparionins severely declined in diversity.
Ecology
In the Old World hipparionins were initially browsers and mixed feeders (both browsing and
grazing
In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...
), over time there was increasing proportion of pure grazers, though the groups ecology remained diverse, with mixed feeding being the dominant ecology during the
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 Hipparionins in the western Mediterranean during the Vallesian and
Turolian
The Turolian age is a period of geologic time (9.0–5.3 Ma) within the Miocene used more specifically with European Land Mammal Ages. It precedes the Ruscinian age and follows the Vallesian age. The Turolian overlaps the Tortonian and Messinia ...
exhibited noticeable niche partitioning, with smaller forms being mixed feeders while larger species had more grazing diets. In contrast, contemporaneous eastern Mediterranean hipparionins did not exhibit such niche partitioning.
Taxonomy
North American genera:
* ''"Hipparion" '' (distinct from Old World species assigned to this genus)
* ''
Neohipparion
''Neohipparion'' (Greek: "new" (neos), "pony" (hipparion)) is an extinction, extinct genus of equid, from the Neogene (Miocene to Pliocene) of North America and Central America. Fossils of this horse have been found in Texas, Florida, Kansas, ...
Nannippus
''Nannippus'' is an extinct genus of three-toed horse endemic to North America during the Miocene through Pleistocene, about 13.3—1.8 million years ago (Mya), living around 11.5 million years. This ancient species of three-toed horse grew up to ...
''
* '' Cormohipparion''
Old World genera: (widely thought to descend from ''Cormohipparion'')
* ''
Hipparion
''Hipparion'' is an extinct genus of three-toed, medium-sized equine belonging to the extinct tribe Hipparionini, which lived about 10-5 million years ago. While the genus formerly included most hipparionines, the genus is now more narrowly defi ...