Hipparionini

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Hipparionini
Temporal range: Early Miocene–Early Pleistocene
Skeleton of Hipparion on display in China
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Subfamily: Equinae
Tribe: †Hipparionini
Quinn, 1955
Genera

See text

Hipparionini is an extinct 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,[1] before migrating into the Old World around 11.4-11.0 million years ago.[2] The youngest species date to the Early Pleistocene, becoming extinct following the arrival of modern equines of the genus Equus to the Old World.[3]

Description

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Hipparionines varied widely in size, with the smallest species like Hipparion periafricanum having a body mass of only 23 kilograms (51 lb), considerably smaller than living equines,[4] while the largest species had body masses over 300 kilograms (660 lb).[2] The smallest species were North American with the smallest Old World hipparionines probably no smaller than 70 kilograms (150 lb).[5] Unlike modern horses, they bore three functional toes on each foot. Their teeth are somewhat lower crowned compared to modern equines, though they had relatively complex enamel patterns that exceed the enamel complexity of teeth of members of the tribe Equini, which is thought to have been an adaption to increasing wear resistance. Compared to modern equines, the metapodial bones of the leg/foot were longer, as is ancestrally found in equids.[6] Some Old World hipparionines like Proboscidipparion developed retracted nasals and elongated snouts that may indicate the presence of a tapir-like proboscis.[5]

Evolutionary history

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Hipparionini originated in North America during the late Early Miocene, around 17 million years ago.[1] In North America, hipparionins were equally diverse to equins during the Middle Miocene but overtook them in species richness during the Late Miocene and Early Pliocene. At the end of the Hemphillian (during the latest Miocene) hipparionins severely declined in diversity.[7] Hipparionines eventually went extinct in North America during the Early Pleistocene, by which time they were confined to the southern latitudes of the continent. Following the end of the Miocene, hipparionines were only represented in North America by very small (sheep-sized) species of Cormohipparion and Nannippus.[5]

Following their origin in North America, a member of the genus Cormohipparion crossed over into Eurasia via the Bering Land Bridge around 11.4-11 million years ago, becoming ancestral to all Old World hipparionines[2][5] which was followed shortly afterwards by a migration into Africa around 10.5 million years ago, though hipparionines did not begin significantly diversifying in Africa until around 7.5 million years ago.[5] During their first few million years in Eurasia, they coexised alongside more primitive anchitheriin horses, which had cross the Bering Land Bridge from North America 8 million years earlier, which subsequently became extinct around 9 million years ago.[8] Hipparionines subsequently diversified in Afro-Eurasia, reaching maximum diversity around 7.6-6.8 million years ago, though at the end of the Miocene, around 6.8-5.3 million years ago, numerous lineages of Old World hipparionine lineages became extinct. During the following Pliocene, Old World hipparionines exhibted developed larger body sizes and higher crowned teeth to cope with environmental change. At the Pliocene-Pleistocene boundary, approximately 2.6 million years ago "stenonine" equines of the genus Equus migrated into Eurasia from North America, providing direct competition with the hipparionines. The last hipparionines in the Old World are Proboscidipparion sinense from China, and Eurygnathohippus cornelianus from Africa, dating to the end of the Early Pleistocene, approximately 1 million years ago.[2]

Ecology

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In North America, Cormohipparion aff. C. quinni from the Barstovian (15-16 mya) and Neohipparion eurystyle from the Hemphillian (early Pliocene 4.7-4.8 mya) of Mexico have been suggested to have been mixed feeders (both browsing and grazing).[9][10]

In the Old World hipparionins were initially browsers and mixed feeders (both browsing and grazing), 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.[2] Hipparionins in the western Mediterranean during the Vallesian and Turolian stages of the late Miocene 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.[11]

Predators of hipparionines likely included sabertooth cats, such as Promegantereon and Machairodus, and amphicyonids (bear-dogs) such as Magericyon and Thaumastocyon, the large mustelid Eomellivora and the bear Indarctos in the late Miocene Batallones fossil site in Spain,[12] and the sabertooth cat Homotherium and the hyena Crocuta in the Pliocene of Hadar, Ethiopia, based on isotopic analysis.[13]

Taxonomy

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North American genera:

Old World genera:[1] (widely thought to descend from Cormohipparion[2])

References

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  1. ^ a b c d Janis, Christine M.; Bernor, Raymond L. (2019-04-12). "The Evolution of Equid Monodactyly: A Review Including a New Hypothesis". Frontiers in Ecology and Evolution. 7. doi:10.3389/fevo.2019.00119. hdl:1983/ede09e37-96f7-4baf-aec5-1bb7766a04e7. ISSN 2296-701X.
  2. ^ a b c d e f Bernor, Raymond L.; Kaya, Ferhat; Kaakinen, Anu; Saarinen, Juha; Fortelius, Mikael (October 2021). "Old world hipparion evolution, biogeography, climatology and ecology". Earth-Science Reviews. 221 103784. Bibcode:2021ESRv..22103784B. doi:10.1016/j.earscirev.2021.103784.
  3. ^ Cirilli, Omar; Pandolfi, Luca; Alba, David M.; Madurell-Malapeira, Joan; Bukhsianidze, Maia; Kordos, Laszlo; Lordkipanidze, David; Rook, Lorenzo; Bernor, Raymond L. (April 2023). "The last Plio-Pleistocene hipparions of Western Eurasia. A review with remarks on their taxonomy, paleobiogeography and evolution". Quaternary Science Reviews. 306 107976. Bibcode:2023QSRv..30607976C. doi:10.1016/j.quascirev.2023.107976. S2CID 257594449.
  4. ^ Orlandi-Oliveras, Guillem; Nacarino-Meneses, Carmen; Koufos, George D.; Köhler, Meike (2018-11-21). "Bone histology provides insights into the life history mechanisms underlying dwarfing in hipparionins". Scientific Reports. 8 (1): 17203. doi:10.1038/s41598-018-35347-x. ISSN 2045-2322. PMC 6249282.
  5. ^ a b c d e Janis, Christine M. (2023), Casanovas-Vilar, Isaac; van den Hoek Ostende, Lars W.; Janis, Christine M.; Saarinen, Juha (eds.), "Asymmetry of Evolutionary Patterns Between New World and Old World Equids and Among New World Equine Tribes", Evolution of Cenozoic Land Mammal Faunas and Ecosystems, Cham: Springer International Publishing, pp. 143–164, doi:10.1007/978-3-031-17491-9_10, ISBN 978-3-031-17490-2, retrieved 2025-10-21
  6. ^ Cantalapiedra, Juan L.; Sanisidro, Oscar; Cantero, Enrique; Prado, Jose Luis; Alberdi, María Teresa (2023), Prins, Herbert H. T.; Gordon, Iain J. (eds.), "Evolutionary Radiation of Equids", The Equids, Cham: Springer International Publishing, pp. 27–45, doi:10.1007/978-3-031-27144-1_2, ISBN 978-3-031-27143-4, retrieved 2025-10-21
  7. ^ Hulbert, Richard C. (Spring 1993). "Taxonomic evolution in North American Neogene horses (subfamily Equinae): the rise and fall of an adaptive radiation". Paleobiology. 19 (2): 216–234. doi:10.1017/S0094837300015888. ISSN 0094-8373. Retrieved 27 November 2024 – via Cambridge Core.
  8. ^ Janis, Christine M.; Franklin, Edward; Baird, C. Nicholas; Tyler, Joshua (2023), Prins, Herbert H. T.; Gordon, Iain J. (eds.), "The Miocene Browsing Horses: Another Way to Be a Successful Large Equid", The Equids, Cham: Springer International Publishing, pp. 47–71, doi:10.1007/978-3-031-27144-1_3, ISBN 978-3-031-27143-4, retrieved 2025-10-20
  9. ^ Bravo-Cuevas, Victor M.; Priego-Vargas, Jaime (August 2009). "Dietary evaluation of a hipparionin horse population from the middle Miocene of Oaxaca, southeastern Mexico". Revista mexicana de ciencias geológicas. 26 (2): 356–366. ISSN 1026-8774.
  10. ^ Pérez-Crespo, Víctor Adrián; Carranza-Castañeda, Oscar; Arroyo-Cabrales, Joaquín; Morales-Puente, Pedro; Cienfuegos-Alvarado, Edith; Otero, Francisco J.; Pérez-Crespo, Víctor Adrián; Carranza-Castañeda, Oscar; Arroyo-Cabrales, Joaquín; Morales-Puente, Pedro; Cienfuegos-Alvarado, Edith; Otero, Francisco J. (April 2017). "Diet and habitat of unique individuals of Dinohippus mexicanus and Neohipparion eurystyle (Equidae) from the late Hemphillian (Hh3) of Guanajuato and Jalisco, central Mexico: stable isotope studies". Revista mexicana de ciencias geológicas. 34 (1): 38–44. ISSN 1026-8774.
  11. ^ Orlandi-Oliveras, Guillem; Köhler, Meike; Clavel, Julien; Scott, Robert; Mayda, Serdar; Kaya, Tanju; Merceron, Glidas (April 2022). "Feeding strategies of circum‑Mediterranean hipparionins during the late Miocene: Exploring dietary preferences related to size through dental microwear analysis". Palaeontologia Electronica. doi:10.26879/990. Retrieved 1 January 2025 – via Palaeontologia Electronica.
  12. ^ Domingo, M. Soledad; Domingo, Laura; Abella, Juan; Valenciano, Alberto; Badgley, Catherine; Morales, Jorge (August 2016). "Feeding ecology and habitat preferences of top predators from two Miocene carnivore-rich assemblages". Paleobiology. 42 (3): 489–507. Bibcode:2016Pbio...42..489D. doi:10.1017/pab.2015.50. hdl:10261/136983. ISSN 0094-8373.
  13. ^ Robinson, Joshua R.; Lazagabaster, Ignacio A.; Rowan, John; Lewis, Margaret E.; Werdelin, Lars; Campisano, Christopher J.; Reed, Kaye E. (May 2025). "Palaeoecology of the Pliocene large carnivore guild at Hadar, Lower Awash Valley, Ethiopia". Journal of Human Evolution. 202 103653. doi:10.1016/j.jhevol.2025.103653. PMID 40174570.