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Scientific reports2021; 11(1); 10156; doi: 10.1038/s41598-021-89440-9

Evolution of Old World Equus and origin of the zebra-ass clade.

Abstract: Evolution of the genus Equus has been a matter of long debate with a multitude of hypotheses. Currently, there is no consensus on either the taxonomic content nor phylogeny of Equus. Some hypotheses segregate Equus species into three genera, Plesippus, Allohippus and Equus. Also, the evolutionary role of European Pleistocene Equus stenonis in the origin of the zebra-ass clade has been debated. Studies based on skull, mandible and dental morphology suggest an evolutionary relationship between North American Pliocene E. simplicidens and European and African Pleistocene Equus. In this contribution, we assess the validity of the genera Plesippus, Allohippus and Equus by cladistic analysis combined with morphological and morphometrical comparison of cranial anatomy. Our cladistic analysis, based on cranial and postcranial elements (30 taxa, 129 characters), supports the monophyly of Equus, denies the recognition of Plesippus and Allohippus and supports the derivation of Equus grevyi and members of the zebra-ass clade from European stenonine horses. We define the following evolutionary steps directly relevant to the phylogeny of extant zebras and asses: E. simplicidens-E. stenonis-E. koobiforensis-E. grevyi -zebra-ass clade. The North American Pliocene species Equus simplicidens represents the ancestral stock of Old World Pleistocene Equus and the zebra-ass clade. Our phylogenetic results uphold the most recent genomic outputs which indicate an age of 4.0-4.5 Ma for the origin and monophyly of Equus.
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Publication Date: 2021-05-12 PubMed ID: 33980921PubMed Central: PMC8114910DOI: 10.1038/s41598-021-89440-9Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research investigates the historical evolution and origin of the Equus genus, including zebras and asses, challenging existing theories and proposing a new lineage based on cranial and postcranial anatomical analysis.

Background of Research

  • The research focuses on the evolution of the genus Equus, which has been a debatable topic with no set consensus on its taxonomic content or phylogeny.
  • Some prevalent hypotheses segregate the Equus species into three different genera: Plesippus, Allohippus, and Equus.
  • This study also explores the hypothesized evolutionary role of European Pleistocene Equus stenonis in the origin of the zebra-ass clade.
  • It is noted that previous studies based on skull, mandible, and dental morphology suggest a link between North American Pliocene E. simplicidens and Pleistocene Equus from Europe and Africa.

Research Methodology

  • This study evaluates the validity of the genera Plesippus, Allohippus, and Equus and the supposed connections between them using cladistic analysis combined with morphological and morphometric comparison of cranial anatomy.
  • The research carries out a cladistic analysis based on cranial and postcranial elements across 30 taxa and 129 characters.

Findings and Conclusion

  • The analysis supports the monophyly of Equus, denies the recognition of Plesippus and Allohippus, and supports the evolution of Equus grevyi and the zebra-ass clade from European stenonine horses.
  • The research outlines an evolutionary pathway for extant zebras and asses, starting with the North American Pliocene species Equus simplicidens, which the study suggests is the ancestral stock of Old World Pleistocene Equus and the zebra-ass clade.
  • Finally, the results uphold most recent genomic outputs indicating an age of 4.0 – 4.5 million years for the origin and monophyly of Equus.

Cite This Article

APA
Cirilli O, Pandolfi L, Rook L, Bernor RL. (2021). Evolution of Old World Equus and origin of the zebra-ass clade. Sci Rep, 11(1), 10156. https://doi.org/10.1038/s41598-021-89440-9

Publication

Scientific reports
ISSN: 2045-2322
NlmUniqueID: 101563288
Country: England
Language: English
Volume: 11
Issue: 1
Pages: 10156
PII: 10156

Researcher Affiliations

Cirilli, Omar
  • Dottorato Regionale Pegaso in Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126, Pisa, Italy. omar.cirilli@phd.unipi.it.
  • Dipartimento di Scienze della Terra, Paleo[Fab]Lab, Università degli Studi di Firenze, Via G. La Pira 4, 50121, Firenze, Italy. omar.cirilli@phd.unipi.it.
Pandolfi, Luca
  • Dipartimento di Scienze della Terra, Paleo[Fab]Lab, Università degli Studi di Firenze, Via G. La Pira 4, 50121, Firenze, Italy. luca.pandolfi@unifi.it.
Rook, Lorenzo
  • Dipartimento di Scienze della Terra, Paleo[Fab]Lab, Università degli Studi di Firenze, Via G. La Pira 4, 50121, Firenze, Italy.
Bernor, Raymond L
  • Laboratory of Evolutionary Biology, Department of Anatomy, College of Medicine, 520 W St. N.W, Washington, DC, 20059, USA.
  • Department of Anthropology, Human Origins Program, Smithsonian Institution, Washington, DC, 20560, USA.

MeSH Terms

  • Animals
  • Biological Evolution
  • Bone and Bones / anatomy & histology
  • Equidae / anatomy & histology
  • Equidae / classification
  • Equidae / genetics
  • Evolution, Molecular
  • Genetic Variation
  • Genotype
  • Horses / anatomy & histology
  • Horses / classification
  • Horses / genetics
  • Phylogeny

Conflict of Interest Statement

The authors declare no competing interests.

References

This article includes 56 references
  1. Skinner MP, Hibbard CW. Early Pleistocene pre-glacial and glacial rocks and faunas of north-central Nebraska. Bull. Am. Mus. Nat. Hist. 1972;148:1–148.
  2. Eisenmann V. Les Chevaux (Equussensulato) fossiles et actuels: cranes et dents jugalessupérieures. Cahiers de Paléonotlogie 1980;15:1–186.
  3. Azzaroli A. Ascent and decline of monodactyl equids: A case for prehistoric overkill. Ann ZoolFenn 1992;28:151–163.
  4. Azzaroli A. Phylogeny of the genus Equus L. Palaeont. Ital. 2002;84:11–16.
  5. Azzaroli A, Voorhies MR. The Genus Equus in North America. The Blancan species. Palaeont. Ital. 1993;80:175–198.
  6. Alberdi MT, Ortiz Jaureguizar E, Prado JL. A quantitative review of European stenonoid horses. J. Paleontol. 1998;72:371–387.
    doi: 10.1017/S0022336000036350google scholar: lookup
  7. Eisenmann V, Baylac M. Extant and fossil Equus (Mammalia, Perissodactyla) skulls: a morphometric definition of the genus Equus. Zool. Scr. 2000;29:89–100.
    doi: 10.1046/j.1463-6409.2000.00034.xgoogle scholar: lookup
  8. Macfadden BJ. Evolution. Fossil horses--evidence for evolution.. Science 2005 Mar 18;307(5716):1728-30.
    doi: 10.1126/science.1105458pubmed: 15774746google scholar: lookup
  9. Orlando L, Ginolhac A, Zhang G, Froese D, Albrechtsen A, Stiller M, Schubert M, Cappellini E, Petersen B, Moltke I, Johnson PL, Fumagalli M, Vilstrup JT, Raghavan M, Korneliussen T, Malaspinas AS, Vogt J, Szklarczyk D, Kelstrup CD, Vinther J, Dolocan A, Stenderup J, Velazquez AM, Cahill J, Rasmussen M, Wang X, Min J, Zazula GD, Seguin-Orlando A, Mortensen C, Magnussen K, Thompson JF, Weinstock J, Gregersen K, Røed KH, Eisenmann V, Rubin CJ, Miller DC, Antczak DF, Bertelsen MF, Brunak S, Al-Rasheid KA, Ryder O, Andersson L, Mundy J, Krogh A, Gilbert MT, Kjær K, Sicheritz-Ponten T, Jensen LJ, Olsen JV, Hofreiter M, Nielsen R, Shapiro B, Wang J, Willerslev E. Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse.. Nature 2013 Jul 4;499(7456):74-8.
    doi: 10.1038/nature12323pubmed: 23803765google scholar: lookup
  10. Palombo MR, Alberdi MT. Light and shadows in the evolution of South European stenonoid horses. Fossil Imprint 2017;73:115–140.
    doi: 10.2478/if-2017-0006google scholar: lookup
  11. Bernor RL. Evolution of early Equus in Italy, Georgia, the Indian Subcontinent, East Africa, and the origins of African zebras. Front. Ecol. Evol. 2019;7:166.
    doi: 10.3389/fevo.2019.00166google scholar: lookup
  12. Barrón-Ortiz CI. What is Equus? Reconciling taxonomy and phylogenetic analyses. Front. Ecol. Evol. 2019;7:343.
    doi: 10.3389/fevo.2019.00343google scholar: lookup
  13. Gazin CL. A study of the fossil horses remains from the Upper Pliocene of Idaho. Proc. U.S. Natl. Mus. 1936;83:281–320.
    doi: 10.5479/si.00963801.83-2985.281google scholar: lookup
  14. Gromova IV. Istorijaloshadej (rodaEquus) v StaromSvete. Chast’ 2. Evoljutsijaiklassifikatsijaroda. Trudy PaleontologicheskogoInstitutaAkademiiNauk SSSR 1949;17:2.
  15. Azzaroli A. The two Villafranchian horses of the Upper Valdarno. Palaeontogr. Ital. 1964;61:1–15.
  16. Eisenmann V. Family Equidae. In: Harris JM, editor. Koobi Fora Research Project; Volume 2. The Fossil Ungulates: Proboscidea, Perissodactyla, and Suidae. Clarendon Press; 1983. pp. 156–214.
  17. Lindsay EH, Opdyke ND, Johnson NM. Pliocene dispersal of the horse Equus and late Cenozoic mammal dispersal events. Nature 1980;287:135–138.
    doi: 10.1038/287135a0google scholar: lookup
  18. Bernor RL, Cirilli O, Wang SQ, Rook L. Equus cf. livenzovenzis from Montopoli, Italy (early Pleistocene; MN16b; ca. 2.6 Ma). Boll. Soc. Paleontol. Ital. 2018;57:203–216.
  19. Rook L. Mammal biochronology (Land Mammal Ages) around the world from the late Miocene to middle Pleistocene and major events in horse evolutionary history. Front. Ecol. Evol. 2019;7:278.
    doi: 10.3389/fevo.2019.00278google scholar: lookup
  20. Sun B, Deng T. The Equus datum and the early radiation of Equus in China. Front Ecol Evol 2019;7:429.
    doi: 10.3389/fevo.2019.00429google scholar: lookup
  21. Carranza-Castañeda O. Dinohippus mexicanus (early-late, late, and latest Hemphillian) and the transition to genus Equus, in Central Mexico faunas. Front. Earth Sci. 2019;7:89.
    doi: 10.3389/feart.2019.00089google scholar: lookup
  22. Cirilli O, Bernor RL, Rook L. New insights on the Early Pleistocene equids from Roca-Neyra (France, Central Europe); implications for the Hipparion LAD and the Equus FAD in Europe. J. Paleontol. 2020.
    doi: 10.1017/jpa.2020.99google scholar: lookup
  23. Flynn LJ, Tedford RH, Qiu Z. Enrichment and stability in the pliocene mammalian fauna of North China. Paleobiology 1991;17:246–265.
    doi: 10.1017/S0094837300010599google scholar: lookup
  24. Vislobokova I, Sotnikova M, Dodonov A. Bio-events and diversity of the Late Miocene-Pliocene mammal faunas of Russia and adjacent areas. In: Reumer JWF, Wessels W, editors. Distribution and Migration of Tertiary Mammals in Eurasia. A Volume in Honor of Hans De Brujin. 2003. pp. 563–574.
  25. Raymo ME, Lisiecki LE, Nisancioglu KH. Plio-Pleistocene ice volume, Antarctic climate, and the global delta18O record.. Science 2006 Jul 28;313(5786):492-5.
    doi: 10.1126/science.1123296pubmed: 16794038google scholar: lookup
  26. Eisenmann V, Deng T. Equus qingyangensis (Equidae, Perissodactyla) of the upper Pliocene of Bajiazui, China: Evidence for North American origin of an Old World lineage distinct from E. stenonis. Quaternaire 2005;2:113–122.
  27. Samson P. Les Equidés fossiles de Roumanie. Geol. Romana 1975;16:165–352.
  28. Eisenmann V. The Equids (Mammalia, Perissodactyla) of Saint-Vallier (Drome, France) and other Plio-Pleistocene European equids. Geobios 2004;37:279–305.
    doi: 10.1016/S0016-6995(04)80019-6google scholar: lookup
  29. Eisenmann V. Pliocene and Pleistocene Equids: Paleontology versus molecular biology. Cour. Forsch. Inst. Senckenerg. 2006;256:71–89.
  30. Zachos J, Pagani M, Sloan L, Thomas E, Billups K. Trends, rhythms, and aberrations in global climate 65 Ma to present.. Science 2001 Apr 27;292(5517):686-93.
    doi: 10.1126/science.1059412pubmed: 11326091google scholar: lookup
  31. Heck L, Wilson LAB, Evin A, Stange M, Sánchez-Villagra MR. Shape variation and modularity of skull and teeth in domesticated horses and wild equids.. Front Zool 2018;15:14.
    doi: 10.1186/s12983-018-0258-9pmc: PMC5907714pubmed: 29713365google scholar: lookup
  32. Orlando L, Metcalf JL, Alberdi MT, Telles-Antunes M, Bonjean D, Otte M, Martin F, Eisenmann V, Mashkour M, Morello F, Prado JL, Salas-Gismondi R, Shockey BJ, Wrinn PJ, Vasil'ev SK, Ovodov ND, Cherry MI, Hopwood B, Male D, Austin JJ, Hänni C, Cooper A. Revising the recent evolutionary history of equids using ancient DNA.. Proc Natl Acad Sci U S A 2009 Dec 22;106(51):21754-9.
    doi: 10.1073/pnas.0903672106pmc: PMC2799835pubmed: 20007379google scholar: lookup
  33. Vilstrup JT, Seguin-Orlando A, Stiller M, Ginolhac A, Raghavan M, Nielsen SC, Weinstock J, Froese D, Vasiliev SK, Ovodov ND, Clary J, Helgen KM, Fleischer RC, Cooper A, Shapiro B, Orlando L. Mitochondrial phylogenomics of modern and ancient equids.. PLoS One 2013;8(2):e55950.
    doi: 10.1371/journal.pone.0055950pmc: PMC3577844pubmed: 23437078google scholar: lookup
  34. Jónsson H, Schubert M, Seguin-Orlando A, Ginolhac A, Petersen L, Fumagalli M, Albrechtsen A, Petersen B, Korneliussen TS, Vilstrup JT, Lear T, Myka JL, Lundquist J, Miller DC, Alfarhan AH, Alquraishi SA, Al-Rasheid KA, Stagegaard J, Strauss G, Bertelsen MF, Sicheritz-Ponten T, Antczak DF, Bailey E, Nielsen R, Willerslev E, Orlando L. Speciation with gene flow in equids despite extensive chromosomal plasticity.. Proc Natl Acad Sci U S A 2014 Dec 30;111(52):18655-60.
    doi: 10.1073/pnas.1412627111pmc: PMC4284605pubmed: 25453089google scholar: lookup
  35. Vekua A. Die Wirbeltierfauna des Villafranchium vin Dmanisi und ihre biostratigraphische Bedeutung. Jahrbuch des Römisch-Germanischen Zentralmuseums Mainz 1995;42:77–180.
  36. MacFadden BJ, Carranza-Castañeda O. Cranium of Dinohippus mexicanus (Mammalia: Equidae) from the Early Pliocene (latest Hemphillian) of Central Mexico, and the origin of Equus. Bull. Florida Mus. Nat. Hist. 2002;43:163–185.
  37. Cirilli O, Pandolfi L, Bernor RL. The Villafranchian perissodactyls of Italy: Knowledge of the fossil record and future research perspectives. Geobios 2020;63:1–21.
    doi: 10.1016/j.geobios.2020.09.001google scholar: lookup
  38. Mihlbachler MC, Rivals F, Solounias N, Semprebon GM. Dietary change and evolution of horses in North America.. Science 2011 Mar 4;331(6021):1178-81.
    doi: 10.1126/science.1196166pubmed: 21385712google scholar: lookup
  39. Cantalapiedra JL, Prado JL, Hernández Fernández M, Alberdi MT. Decoupled ecomorphological evolution and diversification in Neogene-Quaternary horses.. Science 2017 Feb 10;355(6325):627-630.
    doi: 10.1126/science.aag1772pubmed: 28183978google scholar: lookup
  40. Jernvall J, Fortelius M. Common mammals drive the evolutionary increase of hypsodonty in the Neogene.. Nature 2002 May 30;417(6888):538-40.
    doi: 10.1038/417538apubmed: 12037565google scholar: lookup
  41. McDonald H. Population structure of the late Pliocene (Blancan) zebra Equus simplicidens (Perissodactyla: Equidae) from the Hagerman Horse Quarry, Idaho. In: Stewart KM, Seymour KL, editors. Paleoecology and Paleoenvironments of Late Cenozoic Mammals:Tributes to the Career of CS (Rufus) Churcher. University of Toronto Press; 1996. pp. 134–155.
  42. Burke KD, Williams JW, Chandler MA, Haywood AM, Lunt DJ, Otto-Bliesner BL. Pliocene and Eocene provide best analogs for near-future climates.. Proc Natl Acad Sci U S A 2018 Dec 26;115(52):13288-13293.
    doi: 10.1073/pnas.1809600115pmc: PMC6310841pubmed: 30530685google scholar: lookup
  43. Bennett DK. Stripes do not a zebra make, Part I: A cladistic analysis of Equus. Syst. Zool. 1980;29:272–287.
    doi: 10.2307/2412662google scholar: lookup
  44. Antoine PO. Phylogénie et évolution des Elasmotheriina (Mammalia, Rhinocerotidae). Mémoir. Mus. Natl. Hist. 2002;188:1–359.
  45. Antoine PO. A revision of Aceratherium blanfordi Lydekker, 1884 (Mammalia: Rhinocerotidae) from the Early Miocene of Pakistan: postcranials as a key. Zool. J. Linn. Soc.-Lond. 2010;160:139–194.
    doi: 10.1111/j.1096-3642.2009.00597.xgoogle scholar: lookup
  46. Pandolfi L. Persiatherium rodleri, gen. et sp. nov. (Mammalia, Rhinocerotidae), from the Late Miocene of Maragheh (Northwestern Iran). J VertPaleontol. 2015;36:e1040118.
    doi: 10.1080/02724634.2015.1040118google scholar: lookup
  47. Swofford DL. PAUP* (Phylogenetic Analysis Using Parsimony [*and Other Methods] Version 4.0β10. Sinauer; 2001.
  48. Eisenmann V, Alberdi MT, De Giuli C, Staesche U. Methodology. In: Woodburne M, Sondaar PY, editors. Studying fossil horses. EJ Brill Press: Leiden; 1988. pp. 1–71.
  49. Bernor RL, Tobien H, Hayek LAC, Mittmann HW. Hippotherium primigenium (Equidae, Mammalia) from the late Miocene of Höwenegg (Hegau, Germany). Andrias 1997;10:1–230.
  50. R-Development Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/ (2020).
  51. Wickham H. ggplot2: Elegant Graphics for Data Analysis. (ed. Wickham, H.) 1–260 (Springer, 2016).
  52. Venables WN, Ripley BD. Modern Applied Statistics with S. (ed. Venables, W. N. & Ripley, B. D.) 1–498 (Springer, 2008).
  53. Wang SQ, Deng T. Some evolutionary trends of Equus eisenmannae (Mammalia, Perissodactyla) in the stratigraphic sequence of Longdan, China, in comparison to modern Equus. J Vert Paleontol. 2011;31:1356–1365.
    doi: 10.1080/02724634.2011.611203google scholar: lookup
  54. Li Y, Zhang Y, Sun B, Ao H, Xue X. New fossils of the early Pleistocene Equus huanghoensis (Equidae, Perissodactyla) from Nihewan in Hebei province of China. Sci China Earth Sci. 2016;59:83–94.
    doi: 10.1007/s11430-015-5138-ygoogle scholar: lookup
  55. Cirilli O. Target deformation of the Equus stenonis holotype skull: A virtual reconstruction. Front Earth Sci. 2020;8:247.
    doi: 10.3389/feart.2020.00247google scholar: lookup
  56. Eisenmann V. Vera Eisenmann Website. https://vera-eisenmann.com/ (2020).

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  1. Vincelette A. The Characteristics, Distribution, Function, and Origin of Alternative Lateral Horse Gaits. Animals (Basel) 2023 Aug 8;13(16).
    doi: 10.3390/ani13162557pubmed: 37627349google scholar: lookup
  2. Cirilli O, Machado H, Arroyo-Cabrales J, Barrón-Ortiz CI, Davis E, Jass CN, Jukar AM, Landry Z, Marín-Leyva AH, Pandolfi L, Pushkina D, Rook L, Saarinen J, Scott E, Semprebon G, Strani F, Villavicencio NA, Kaya F, Bernor RL. Evolution of the Family Equidae, Subfamily Equinae, in North, Central and South America, Eurasia and Africa during the Plio-Pleistocene. Biology (Basel) 2022 Aug 24;11(9).
    doi: 10.3390/biology11091258pubmed: 36138737google scholar: lookup
  3. Goodchild OA, Rosen SN, Mennecart B, Meng J, Tissier J. The petrosal and bony labyrinth of extinct horses (Perissodactyla, Equidae) and their implications for perissodactyl evolution. PeerJ 2026;14:e20484.
    doi: 10.7717/peerj.20484pubmed: 41522509google scholar: lookup
  4. Ali M. Tibetan wild ass, Equus kiang, in the literature: a comprehensive review. J Equine Sci 2025;36(4):115-127.
    doi: 10.1294/jes.36.115pubmed: 41409899google scholar: lookup
  5. Mallet C, Houssaye A. Deciphering the influence of evolutionary legacy and functional constraints on the patella: an example in modern rhinoceroses amongst perissodactyls. PeerJ 2024;12:e18067.
    doi: 10.7717/peerj.18067pubmed: 39469593google scholar: lookup
  6. Massari S, Giannico F, Paolillo NV, Pala A, Jambrenghi AC, Antonacci R. Genomic and comparative analysis of the T cell receptor gamma locus in two Equus species. Front Immunol 2023;14:1264949.
    doi: 10.3389/fimmu.2023.1264949pubmed: 37781375google scholar: lookup
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