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Hippidion

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Hippidion
Temporal range: Late Pliocene-Holocene (Uquian-Lujanian)
~2.5–0.011 Ma
↓
brown skeleton of a quadruped
H. principale skeleton
Scientific classification Edit this classification
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
  • Onohippidion Filhol 1888
  • Onohippidium Moreno 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.

Taxonomy

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Evolution

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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

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Skeleton in Natural History Museum, London
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

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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

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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

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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 Late Pleistocene megafauna extinctions, 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), as well as the similarly aged Cueva del Medio site in southern Chile 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][16]

References

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  1. ^ a b Weinstock, J.; et al. (2005). "Evolution, systematics, and phylogeography of Pleistocene horses in the New World: a molecular perspective". PLOS Biology. 3 (8): e241. doi:10.1371/journal.pbio.0030241. PMC 1159165. PMID 15974804.
  2. ^ a b Orlando, L.; et al. (2008). "Ancient DNA Clarifies the Evolutionary History of American Late Pleistocene Equids". Journal of Molecular Evolution. 66 (5): 533–538. Bibcode:2008JMolE..66..533O. doi:10.1007/s00239-008-9100-x. PMID 18398561. S2CID 19069554.
  3. ^ a b Der Sarkissian, Clio; Vilstrup, Julia T.; Schubert, Mikkel; Seguin-Orlando, Andaine; Eme, David; Weinstock, Jacobo; Alberdi, Maria Teresa; Martin, Fabiana; Lopez, Patricio M.; Prado, Jose L.; Prieto, Alfredo (March 2015). "Mitochondrial genomes reveal the extinct Hippidion as an outgroup to all living equids". Biology Letters. 11 (3): 20141058. doi:10.1098/rsbl.2014.1058. ISSN 1744-9561. PMC 4387498. PMID 25762573.
  4. ^ a b Heintzman, P.D.; Zazula, G.D.; MacPhee, R.D.E; Scott, E.; Cahill, J.A.; McHorse, B.K.; Kapp, J.D.; Stiller, M.; Wooller, M.J.; Orlando, L.; Southon, J.; Froese, D.G.; Shapiro, B. (2017). "A new genus of horse from Pleistocene North America". eLife. 6. doi:10.7554/eLife.29944. PMC 5705217. PMID 29182148.
  5. ^ a b Santos Avilla, Leonardo Dos; Bernardes, Camila; Mothé, Dimila (2015-05-04). "A new genus for Onohippidium galushai Macfadden and Skinner, 1979 (Mammalia, Equidae), from the late Hemphillian of North America". Journal of Vertebrate Paleontology. 35 (3): e925909. Bibcode:2015JVPal..35E5909S. doi:10.1080/02724634.2014.925909. ISSN 0272-4634.
  6. ^ a b MacFadden, B. J., and M. Skinner. 1979. Diversification and biogeography of the one-toed horses Onohippidium and Hippidion. Yale Peabody Museum of Natural History Postilla 175:1–9.
  7. ^ Prado, José; Alberdi, María (2023). "Diversity of the fossil equidsfrom South America". Publicación Electrónica de la Asociación Paleontológica Argentina. 23 (1): 241–254. doi:10.5710/PEAPA.06.06.2022.415.
  8. ^ a b Labarca, Rafael; Caro, Francisco J.; Villavicencio, Natalia A.; Capriles, José M.; Briones, Esteban; Latorre, Claudio; Santoro, Calogero M. (2020-12-10). "A partially complete skeleton of Hippidion saldiasi Roth, 1899 (Mammalia: Perissodactyla) from the late Pleistocene of the high Andes in northern Chile". Journal of Vertebrate Paleontology. 40 (6): e1862132. Bibcode:2020JVPal..40E2132L. doi:10.1080/02724634.2020.1862132. ISSN 0272-4634. S2CID 233706381.
  9. ^ Prado, José Luis; Alberdi, María Teresa (2017), "Nomenclatures and Taxonomy", Fossil Horses of South America, Cham: Springer International Publishing, pp. 7–59, doi:10.1007/978-3-319-55877-6_2, ISBN 978-3-319-55876-9, retrieved 2024-01-19
  10. ^ Bernardes, Camila; Sicuro, Fernando L.; Avilla, Leonardo S.; Pinheiro, André E.P. (2012). "Rostral reconstruction of South American hippidiforms (Mammalia, Perissodactyla, Equidae): New anatomical and ecomorphological inferences". Acta Palaeontologica Polonica. doi:10.4202/app.2011.0107.
  11. ^ Prado, José L; Sánchez, Begoña; Alberdi, María T (December 2011). "Ancient feeding ecology inferred from stable isotopic evidence from fossil horses in South America over the past 3 Ma". BMC Ecology. 11 (1): 15. Bibcode:2011BMCE...11...15P. doi:10.1186/1472-6785-11-15. ISSN 1472-6785. PMC 3129290. PMID 21672241.
  12. ^ Prado, José Luis; Alberdi, María Teresa (2017), "Ancient Feeding Ecology and Niche Differentiation of Pleistocene Horses", Fossil Horses of South America, Cham: Springer International Publishing, pp. 101–118, doi:10.1007/978-3-319-55877-6_6, ISBN 978-3-319-55876-9, retrieved 2024-01-20
  13. ^ Morosi, Elizabeth; Ubilla, Martin (December 2019). "Feeding and environmental studies on late Pleistocene horses in mid-latitudes of South America (northern Uruguay)". Quaternary Science Reviews. 225: 106025. Bibcode:2019QSRv..22506025M. doi:10.1016/j.quascirev.2019.106025. S2CID 210240458.
  14. ^ Villavicencio, Natalia A.; Corcoran, Derek; Marquet, Pablo A. (2019-06-27). "Assessing the Causes Behind the Late Quaternary Extinction of Horses in South America Using Species Distribution Models". Frontiers in Ecology and Evolution. 7: 226. doi:10.3389/fevo.2019.00226. ISSN 2296-701X.
  15. ^ Bampi, Hugo; Barberi, Maira; Lima-Ribeiro, Matheus S. (December 2022). "Megafauna kill sites in South America: A critical review". Quaternary Science Reviews. 298: 107851. Bibcode:2022QSRv..29807851B. doi:10.1016/j.quascirev.2022.107851. S2CID 253876769.
  16. ^ Nami, Hugo G. (2019-08-12). "Paleoamerican Occupation, Stone Tools from the Cueva del Medio, and Considerations for the Late Pleistocene Archaeology in Southern South America". Quaternary. 2 (3): 28. doi:10.3390/quat2030028. hdl:11336/120270. ISSN 2571-550X.
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