Hipparion

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Hipparion
Temporal range: Late Miocene 9.9–5.3  Ma
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Hipparion NNHM.jpg
Skeleton on display at the National Natural History Museum of China
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Subfamily: Equinae
Tribe: Hipparionini
Genus: Hipparion
De Christol, 1832
Species

See text

Synonyms
  • Hemihipparion

Hipparion is an extinct genus of three-toed, medium-sized equine belonging to the extinct tribe Hipparionini, who lived about 10-5 million years ago. [1] [2] While the genus formerly included most hipparionines, the genus is now more narrowly defined as hipparionines from Eurasia spanning the Late Miocene. [2] Hipparion was a mixed-feeder who ate mostly grass, and lived in the savannah biome. [2] [3] Hipparion evolved from Cormohipparion , [2] and went extinct due to environmental changes like cooling climates and decreasing atmospheric carbon dioxide levels. [4]

Contents

Taxonomy

"Hipparion" in sensu lato

The genus "Hipparion" was used for over a century as a form classification to describe over a hundred species of Holartic hipparionines from the Pliocene and Miocene eras that had three toes and isolated protocones. Since then, groups such as the genera Cormohipparion and Neohipparion were proposed to further sort these species, typically based on differences in skull morphology. These species are now known as "Hipparion" in sensu lato (s.l.), or a broad sense. [5]

Hipparion in sensu stricto

Hipparion in sensu stricto (s.s.), or a strict sense, describes the genus of Old World hipparionines from remains found in Eurasia (France, Greece, Turkey, Iran, and China) from the Late Miocene era (~10-5 Ma, or million years ago). The assignment of remains from elsewhere to the genus, such as North America and Africa, is uncertain. [2]

Morphology

Life reconstruction of H. forcei Hipparion forcei NT.jpg
Life reconstruction of H. forcei
H. gracile skull Hipparion gracile skull.jpg
H. gracile skull
Three-toed Hipparion hind leg fossil Fossil Hipparion in Haining Museum 02 2014-08.JPG
Three-toed Hipparion hind leg fossil

Limbs

Hipparion generally resembled a smaller version of the modern horse, but was tridactyl, or three-toed. It had two vestigial outer toes on each limb in addition to its hoof. [2] In some species, these outer toes were functional. [6]

Size

Hipparion was typically medium in size, at about 1.4 m (4.6 ft) tall at the shoulder. [7] [8] The estimated body mass of Hipparion depends on the species, but ranges from about 135 to 200 kg (about 298 to 441 lbs). [2]

Skull

Hipparion had hypsodont dentition (high-crowned teeth) for its premolars and molars, with a crown height of about 60 mm (2.36 in). Hipparion had isolated protocones in the upper molars, meaning a cusp of the teeth called a protocone was not connected to a tooth crest called a protoloph. [2] Hipparion is also characterized by its facial fossa, or deep depression in the skull, located high on the head in front of the orbit. [9] [10]

Life

Mauricio Anton's illustration of Hipparion cornelianum that resembles a modern-day zebra Hipparion cornelianum.jpg
Mauricio Antón's illustration of Hipparion cornelianum that resembles a modern-day zebra

Habitat and diet

Hipparion lived in the Old World Savannah Biome, or OWSB, consisting of woodlands to grasslands. [2] Hipparion ate a mixed-feed diet, mostly consisting of grass. This diet is indicated by fossil evidence of microscopic wear patterns of scratches and pits on the enamel of Hipparion's teeth, observed using scanning electron microscopy (SEM). [3]

Lifespan

Hipparion achieved skeletal maturity and possibly sexual maturity at about 3 years old. Fossils of Hipparion individuals are up to 10 years old at death. [8]

Evolution and extinction

Evolution

Hipparion likely evolved from a species of Cormohipparion during the Late Miocene, about 11.4-11.0 Ma. This species, C. occidentale, came to Eurasia and Africa from North America. [2] The last common ancestor of Hipparion and the modern horse was Merychippus. [11]

Extinction

In the Old World, Hipparion experienced population decline and extinction down a North to South gradient, as did many other Miocene vertebrates. This trend is believed to be due to environmental changes caused by global cooling and decreasing carbon dioxide levels in the atmosphere. [4]

Species

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. It is more specifically grouped within the superfamily Equoidea, the only other family being the extinct Palaeotheriidae.

<i>Merychippus</i> Extinct genus of horses

Merychippus is an extinct proto-horse of the family Equidae that was endemic to North America during the Miocene, 15.97–5.33 million years ago. It had three toes on each foot and is the first horse known to have grazed.

<span class="mw-page-title-main">Gomphothere</span> Extinct family of proboscidean mammals

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 as part of the Great American Interchange. Gomphotheres are a paraphyletic group ancestral to Elephantidae, which contains modern elephants, as well as Stegodontidae.

<i>Chasmaporthetes</i> Extinct genus of carnivores

Chasmaporthetes, also known as hunting or running hyena, is an extinct genus of hyenas distributed in Eurasia, North America, and Africa during the Pliocene-Pleistocene epochs, living from 4.9 million to 780,000 years ago, existing for about 4.12 million years. The genus probably arose from Eurasian Miocene hyenas such as Thalassictis or Lycyaena, with C. borissiaki being the oldest known representative. The species C. ossifragus was the only hyena to cross the Bering land bridge into the Americas, and ranged over what is now Arizona and Mexico during Blancan and early Irvingtonian Land Mammal ages, between 5.0 and 1.5 million years ago.

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

Ancylotherium is an extinct genus of the family Chalicotheriidae, subfamily Schizotheriinae, endemic to Europe, Asia, and Africa during the Late Miocene-Early Pleistocene, existing for approximately 9.8 million years.

<i>Gomphotherium</i> Extinct genus of elephant-like mammals

Gomphotherium is an extinct genus of gomphothere proboscidean from the Neogene of Eurasia, Africa and North America. It is the most diverse genus of gompothere, with over a dozen valid species. The genus is probably paraphyletic.

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

Hippidion 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.

<span class="mw-page-title-main">Evolution of the horse</span>

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 in the horse family native to North America during the Pliocene and Early Pleistocene. It is one of the oldest and most primitive members of the genus Equus. It is the state fossil of Idaho, where its abundant remains were discovered in 1928, specifically in Hagerman, Idaho. They are also known from other US states including Arizona, California, Texas, Nebraska and Kansas.

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

Pseudhipparion is an extinct genus of three-toed horse endemic to North America during the Miocene. They were herding animals whose diet consisted of C3 plants. Fossils found in Georgia and Florida indicate that it was a lightweight horse, weighing up to 90 pounds. In 2005, fossils were unearthed in Oklahoma. Seven species of Pseudhipparion are known from the fossil record which were very small, following the trend of Bergmann's rule.

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

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 3.5 feet and weighed between 165 pounds to 199 pounds, which was around the same size as a domestic sheep.

<i>Cormohipparion</i> Extinct genus of horse

Cormohipparion is an extinct genus of horse belonging to the tribe Hipparionini that lived in North America during the late Miocene to Pliocene. They grew up to 3 feet long.

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

Hippotherium is an extinct genus of horse that lived in during the Miocene through Pliocene ~13.65—6.7 Mya, existing for 6.95 million years.

<span class="mw-page-title-main">Hipparionini</span> Extinct tribe of mammals

Hipparionini is a tribe of three-toed horses in the subfamily Equinae. 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 around 11.4-11.0 million years ago. The youngest species date to the Early Pleistocene.

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

Eurygnathohippus is an extinct genus of hipparionine horse. The majority of known fossils of members of this genus were discovered in Africa, where members of this genus lived during the late Miocene to Pleistocene interval. Fossils of Eurygnathohippus were also reported from the late Pliocene sediments of the Potwar Plateau in Pakistan and the Siwalik Hills in northwest India.

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

Cremohipparion is an extinct genus of horse living in Eurasia and Africa during the Miocene through Pliocene.

This paleomammalogy list records new fossil mammal taxa that were described during the year 2013, as well as notes other significant paleomammalogy discoveries and events which occurred during that year.

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

Sivalhippus is an extinct genus of horse that lived in Africa and the Indian subcontinent during the late Miocene.

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

Bunolistriodon is an extinct genus of pig-like animals from Eurasia and Africa during the Miocene.

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

Proboscidipparion is an extinct genus of hipparionine equine. It is named after its unusual retracted nasal region of the skull, which may have supported a proboscis. Fossils have been found throughout Eurasia, from England to China. The oldest specimens are known from Asia, dating to the Early Pliocene, around 5.3-5 million years ago. The genus was one of the last surviving hipparionines, with the youngest specimen dating to the end of the Early Pleistocene, around 1 million years ago.

References

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