Hipparion

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Hipparion
Temporal range: Late Miocene 9.9–5.3 
Ma
↓
H. laromae skeleton
Scientific classification Edit this classification
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

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]

Taxonomy

"Hipparion" in sensu lato

The genus "Hipparion" was used for over a century as a

sensu lato (s.l.), or a broad sense.[5]

Hipparion in sensu stricto

Hipparion in

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
Skull of H. gracile against a black background
H. gracile skull
Fossil of three-toed Hipparion lower hind leg, held up on a stand and against a brown cloth background
Three-toed Hipparion hind leg fossil

Limbs

Hipparion generally resembled a smaller version of the

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

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

Habitat and diet

Hipparion lived in the Old World Savannah

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 have been found to be up to 10 years old at the time of 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

  • H. chiai Liu et al., 1978
  • H. concudense Pirlot, 1956
  • H. condoni Merrian, 1915
  • H. crassum Gervais, 1859
  • H. dietrichi Wehrli, 1941
  • H. fissurae Crusafont and Sondaar, 1971
  • H. forcei Richey, 1948
  • H. gromovae Villalta and Crusafont, 1957
  • H. laromae Pesquero et al., 2006
  • H. longipes Gromova, 1952
  • H. lufengense Sun, 2013
  • H. macedonicum Koufos, 1984
  • H. matthewi Abel, 1926
  • H. mediterraneum Roth and Wagner, 1855
  • H. molayanense Zouhri, 1992
  • H. minus Pavlow, 1890
  • H. periafricanum Villalta and Crusafont, 1957
  • H. philippus Koufos & Vlachou, 2016
  • H. phlegrae Lazaridis and Tsoukala, 2014
  • H. prostylum Gervais, 1849 (type)
  • H. rocinantis Pacheco, 1921
  • H. sellardsi Matthew and Stirton, 1930
  • H. shirleyae MacFadden, 1984
  • H. sithonis Koufos & Vlachou, 2016
  • H. sitifense Pomel, 1897
  • H. tchicoicum Ivanjev, 1966[12]
  • H. tehonense (Merriam, 1916)
  • H. theniusi Melentis, 1969
  • H. venustum Leidy, 1860

References

  1. ISSN 0277-3791
    .
  2. ^
    doi:10.1016/j.earscirev.2021.103784
    .
  3. ^
    doi:10.1146/annurev.ecolsys.31.1.33
    – via JSTOR.
  4. ^
    doi:10.1127/njgpa/2022/1037
    – via Schweizerbart Science Publishers.
  5. ^ MacFadden, Bruce J. (August 1980). "The Miocene horse Hipparion from North America and from the type locality in Southern France". Paleontology. 23 (3): 617–635 – via The Paleontological Association.
  6. ISBN 9781443417860
    .
  7. ISBN 1-84028-152-9
    .
  8. ^
    PMID 25098950
    .
  9. ISSN 0272-4634
    .
  10. ISBN 0-716-71822-7
    .
  11. PMID 28183978
    .
  12. PMID 37186049
    .
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