Hippidion

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Hippidion
Temporal range: Late Pliocene-Holocene (Uquian-Lujanian)
~2.5–0.011  Ma
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Hippidion principale skeleton.JPG
H. principale skeleton
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Subfamily: Equinae
Tribe: Equini
Genus: Hippidion
Owen, 1869
Species
  • H. principale (Lund, 1846) (type)
  • H. saldiasi Roth, 1899
  • H. devillei (Gervais, 1855)
Synonyms
  • Hipphaplous Ameghino 1882
  • Hipphaplus Ameghino 1882
  • OnohippidionFilhol 1888
  • OnohippidiumMoreno 1891
  • Parahipparion Ameghino 1904

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 .

Contents

Taxonomy

Evolution

Although early ancient DNA analysis studies suggested a close relationship with the wild horse, Equus ferus, [1] [2] 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 North American "New World stilt legged horse", Haringtonhippus francisci. Cladogram shown below: [4]

Equini

Hippidion

Haringtonhippus

Genus  Equus

Equus ferus (wild horse)

Equus ovodovi

Subgenus Asinus (asses)

Subgenus Hippotigris (zebras)

Hippidion is part of a distinct lineage of equines belonging to the tribe Equini that are suggested to have diverged from the ancestors of living equines of the genus Equus at least 6 million years ago. [4] The earliest members of the Hippidion lineage are known from the Late Miocene of North America. [5] [6] Hippidion migrated into the South American continent at the Pliocene-Pleistocene transition, around 2.5 million years ago as part of the Great American Biotic Interchange [1] [2] with the hippidiform lineage becoming extinct in North America during the Early Pleistocene. [5] It is disputed as to whether Hippidion is an exclusively South American genus or whether remains from North America are attributable to it. [7] [6]

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, while H. devillei was found to be clearly genetically distinct. [3]

Description

Skeleton in Natural History Museum, London Hippidion 23.JPG
Skeleton in Natural History Museum, London
Reconstruction of skull musculature with proposed prehensile lip Hippidion skull muscles.jpg
Reconstruction of skull musculature with proposed prehensile lip

Specimens of Hippidion saldiasi have been estimated to weigh in the range of 252.7–326.4 kilograms (557–720 lb), while specimens of H. devillei have been estimated to weigh in the region of 227.3–366.5 kilograms (501–808 lb). H. principale was somewhat larger, with an estimated mass range of 252.7–468.6 kilograms (557–1,033 lb). [8] The skull of Hippidion is noted for its very long nasal notch separating the elongate nasal bone from the rest of the skull. [9] This structure is suggested to correspond to the presence of a prehensile upper lip. [10]

Paleobiology

Restoration of a Hippidion browsing with prehensile lips. South American Pleistocene equids.jpg
Restoration of a Hippidion browsing with prehensile lips.

Isotopic evidence from δ13C suggests that Hippidion consumed plants of either C3 or mixed C3 and C4 type carbon fixation. [11] The δ13C values are consistent with the occupation of woodland and wooded grassland habitats. [12] 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. [13]

Distribution

Fossils of Hippidion have been found across South America. Hippidion principale is primarily known from the Pampas grasslands of Argentina, but its range may have extended to Peru and Ecuador. Hippidion devillei is also known from Argentinan Pampas, but is also found in the Peruvian central Andes, with remains possibly found in Venezuela. Hippidion saldiasi was native to the Southern Cone, including Patagonia and the southern Andes. [8]

Extinction

Hippidion became extinct alongside the other South American equines at the end of the Late Pleistocene, between 12,000 and 10,000 years Before Present (BP) as part of the Quaternary extinction event, which resulted in the extinction of most large animals in both North and South America. Climatic modelling suggests that the preferred habitat for species of Hippidion declined after the Holocene transition, but the decline is not enough to explain the extinction. [14] At the Arroyo Seco 2 site in the Argentinan Pampas (14,782–11,142 cal yr BP), and Piedra Museo site in Santa Cruz Province, Patagonia (two separate layers dating to 12,463–10,457 cal yr BP and 15,517–12,352 cal yr BP), remains of Hippidion are associated with human artifacts, including Fishtail projectile points, and bear cut marks, indicating that they were hunted by recently arrived humans, which may have played a role in their extinction. [15]

Related Research Articles

<span class="mw-page-title-main">Equidae</span> Family of hoofed mammals

Equidae is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. The family evolved around 50 million years ago from a small, multi-toed ungulate into larger, single-toed animals. All extant species are in the genus Equus, which originated in North America. Equidae belongs to the order Perissodactyla, which includes the extant tapirs and rhinoceros, and several extinct families.

<i>Megatherium</i> Genus of ground sloth (extinct)

Megatherium is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Pleistocene. It is best known for the elephant-sized type species M. americanum, sometimes known as the giant ground sloth, or the megathere, native to the Pampas through southern Bolivia during the Pleistocene. Various other smaller species belonging to the subgenus Pseudomegatherium are known from the Andes.

<i>Equus</i> (genus) Genus of mammals which includes horses, donkeys, and zebras

Equus is a genus of mammals in the family Equidae, which includes horses, asses, and zebras. Within the Equidae, Equus is the only recognized extant genus, comprising seven living species. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. The genus most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes, and long tails. All species are herbivorous, and mostly grazers, with simpler digestive systems than ruminants but able to subsist on lower-quality vegetation.

<span class="mw-page-title-main">American lion</span> Extinct species of carnivore

Panthera atrox, better known as the American lion, also called the North American lion, or American cave lion, is an extinct pantherine cat. Panthera atrox lived in North America during the Pleistocene epoch, from around 340,000 to 12,800 years ago. The species was initially described by American paleontologist Joseph Leidy in 1853 based on a fragmentary mandible (jawbone) from Mississippi; the species name ('atrox') means "savage" or "cruel". The status of the species is debated, with some mammalogists and paleontologists considering it a distinct species or a subspecies of Panthera leo, which contains living lions. However, novel genetic evidence has shown that it is instead a distinct species derived from the Eurasian cave or steppe lion, evolving after its geographic isolation in North America. Its fossils have been excavated from Alaska to Mexico. It was about 25% larger than the modern lion, making it one of the largest known felids.

<span class="mw-page-title-main">Wild horse</span> Undomesticated four-footed mammal from the equine family

The wild horse is a species of the genus Equus, which includes as subspecies the modern domesticated horse as well as the endangered Przewalski's horse. The European wild horse, also known as the tarpan, that went extinct in the late 19th or early 20th century has previously been treated as the nominate subspecies of wild horse, Equus ferus ferus, but more recent studies have cast doubt on whether tarpans were truly wild or if they actually were feral horses or hybrids.

<span class="mw-page-title-main">European wild ass</span> Extinct species of mammal

The European wild ass or hydruntine is an extinct equine from the Middle Pleistocene to Late Holocene of Europe and West Asia, and possibly North Africa. It is a member of the subgenus Asinus, and closely related to the living Asiatic wild ass. The specific epithet, hydruntinus, means from Otranto.

<i>Cuvieronius</i> Extinct genus of mammals

Cuvieronius is an extinct New World genus of gomphothere which ranged from southern North America to western South America during the Pleistocene epoch. Among the last gomphotheres, it became extinct at the end of the Pleistocene, approximately 12,000 years ago, following the arrival of humans to the Americas.

<i>Stegomastodon</i> Extinct genus of mammals

Stegomastodon is an extinct genus of gomphotheres, a family of proboscideans. It ranged throughout North America from the early Blancan ~4 Ma, to the early Irvingtonian. The South American species have been synonymized with Notiomastodon platensis.

<span class="mw-page-title-main">Evolution of the horse</span> Derivation of horses from an ungulate precursor

The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the modern horse than of any other animal. Much of this evolution took place in North America, where horses originated but became extinct about 10,000 years ago, before being reintroduced in the 15th century.

<span class="mw-page-title-main">Hagerman horse</span> Extinct species of mammal

Equus simplicidens, sometimes known as the Hagerman horse or the American Zebra is an extinct species of equine native to North America during the Pliocene and Early Pleistocene. It is one of the oldest and most primitive members of the genus Equus. Abundant remains of it were discovered in 1928 in Hagerman, Idaho. It is the state fossil of Idaho.

<span class="mw-page-title-main">Late Pleistocene extinctions</span> Extinction event occurring during the late Quaternary period

The Late Pleistocene to the beginning of the Holocene saw numerous extinctions of predominantly megafaunal animal species, which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by the widespread absence of ecological succession to replace these extinct megafaunal species, and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are thought to have been driven by varying combinations of human and climatic factors. Human impact on megafauna populations is thought to have been driven by hunting ("overkill"), as well as possibly environmental alteration. The relative importance of human vs climatic factors in the extinctions has been the subject of long-running controversy.

<i>Glyptodon</i> Genus of large, heavily armored mammals

Glyptodon is a genus of glyptodont, an extinct group of large, herbivorous armadillos, that lived from the Pliocene, around 3.2 million years ago, to the early Holocene, around 11,000 years ago, in Brazil, Uruguay, Paraguay, Bolivia, Peru, Argentina, and Colombia. It is one of, if not the, best known genus of glyptodont. Glyptodon has a long and storied past, being the first named extinct cingulate and the type genus of the subfamily Glyptodontinae. Fossils of Glyptodon have been recorded as early as 1814 from Pleistocene aged deposits from Uruguay, though many were incorrectly referred to the ground sloth Megatherium by early paleontologists.

<i>Haringtonhippus</i> Extinct genus of mammals

Haringtonhippus is an extinct genus of equine from the Pleistocene of North America The genus is monospecific, consisting of the species H. francisci, initially described in 1915 by Oliver Perry Hay as Equus francisci. Members of the genus are often referred to as stilt-legged horses, in reference to their slender distal limb bones, in contrast with those of contemporary "stout legged" caballine true horses.

<span class="mw-page-title-main">Equinae</span> Subfamily of mammals

Equinae is a subfamily of the family Equidae, known from the Hemingfordian stage of the Early Miocene onwards. They originated in North America, before dispersing to every continent except Australia and Antarctica. They are thought to be a monophyletic grouping. Members of the subfamily are referred to as equines; the only extant equines are the horses, asses, and zebras of the genus Equus, with two other genera Haringtonhippus and Hippidion becoming extinct at the beginning of the Holocene, around 11-12,000 years ago.

<i>Notiomastodon</i> Extinct genus of mammals

Notiomastodon is an extinct genus of gomphothere proboscidean, endemic to South America from the Pleistocene to the beginning of the Holocene. Notiomastodon specimens reached a size similar to that of the modern Asian elephant. Like other brevirostrine gomphotheres such as Cuvieronius and Stegomastodon, Notiomastodon had a shortened lower jaw and lacked lower tusks.

<i>Arctotherium</i> Extinct genus of bears

Arctotherium is an extinct genus of the Pleistocene short-faced bears endemic to Central and South America. Arctotherium migrated from North America to South America during the Great American Interchange, following the formation of the Isthmus of Panama during the late Pliocene. The genus consists of one early giant form, A. angustidens, and several succeeding smaller species, which were within the size range of modern bears. Arctotherium was adapted to open and mixed habitat. They are genetically closer to the spectacled bear, than to Arctodus of North America, implying the two extinct forms evolved large size in a convergent manner.

<i>Equus neogeus</i> Extinct species of equine native to South America

Equus neogeus is an extinct species of equine native to South America during the Pleistocene. 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.

<span class="mw-page-title-main">Fishtail projectile point</span> Type of projectile point used in South America during the Late Pleistocene

Fishtail points, also known as Fell points are a style of Paleoindian projectile point widespread in South America at the end of the Late Pleistocene. Their chronological timing is disputed, with some authors favouring a short chronology spanning 12,800–12,200 years Before Present (BP), while others favouring a long chronology spanning 13,500–10,200 years BP. It is the earliest widespread lithic style in South America, being contemporaneous in its earlier stages to the use of Clovis points in North America. Fishtail points may be derived from Clovis points, or possibly from Fishtail-like points found on the Gulf Coast of North America and in Central America.

Equus ovodovi is an extinct species of equine known from the Late Pleistocene and Holocene of Northern and East Asia.

The Dolores Formation is a Lujanian geologic formation in Uruguay.

References

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