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Equus (horse)

Mammalia - Perissodactyla - Equidae

Discussion

The genus Equus includes many extinct species in addition to the living domestic horse, zebras, and asses. It originated in North America and emigrated to the Old World during the Pliocene. In the 1920s a spectacular mass mortality assemblage of the primitive species Equus simplicidens was found at the Gidley Horse Quarry in Idaho. Before the end-Pleistocene megafaunal mass extinction several species of horses lived in North America. Pleistocene horses fossils are very common, but their taxonomy is still poorly resolved because many of the older species names were based on poor type specimens.

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Synonyms
Synonymy list
YearName and author
1758Equus Linnaeus p. 73
1762Onager Brisson
1822Asinus Gray
1825Asinus Gray p. 342
1841Hippotigris Hamilton-Smith
1846Asinus Owen
1848Equus Owen p. 139
1858Asinus africanus Fitzinger
1860Equus Leidy p. 100
1861Equus taeniopus Heuglin
1873Equus Leidy p. 321
1881Equus Cope p. 400
1884Asinus Noack
1884Asinus taeniopus Noack
1890Hippotherium princeps Leidy p. 182
1892Tomolabis Cope p. 125
1893Equus semiplicatus Cope p. 80
1896Hippotherium princeps Leidy and Lucas p. 49
1896Hipparion princeps Roger
1901Equus semiplicatus Gidley p. 129 fig. 20
1902Equus Hay p. 621
1902Equus semiplicatus Hay p. 624
1907Equus Gidley p. 867
1907Neohipparion princeps Gidley p. 910
1912Dolichohippus Heller
1912Equus (Grevya) Hilzheimer
1912Equus (Megacephalon) Hilzheimer
1913Neohippus Abel
1913Equus (Ludolphozecora) Griffini p. 382
1913Equus leidyi Hay p. 572
1913Equus Scott p. 291
1916Equus (Asinus) Lydekker
1916Equus asinus taeniopus Lydekker
1926Equus Oliver Schneider p. 149
1930Kolpohippus van Hoepen
1930Kraterohippus van Hoepen
1930Sterrohippus van Hopen
1935Asinus Dollman
1935Equus Schultz and Howard p. 285
1940Equus Stirton p. 194
1942Asinus Hopwood
1944Hippotigris McGrew
1945Asinus Harper
1955Equus Hibbard p. 51
1955Hippotigris Quinn p. 46
1955Asinus Quinn p. 52
1955Equus Quinn p. 58
1957Onager Quinn p. 10
1957Onager semiplicatus Quinn p. 10
1957Asinus Quinn p. 27
1957Equus Quinn p. 27
1958Hippotigris Mooser p. 360
1958Asinus Quinn
1959Asinus Mooser
1959Equus parastylidens Mooser
1961Allozebra Trumler
1961Asinus Trumler
1961Hippotigris Trumler
1972Equus (Amerhippus) Skinner p. 118
1972Equus (Dolichohippus) Skinner p. 118
1972Equus (Hippotigris) Skinner p. 118
1975Equus (Parastilidequus) Mooser and Dalquest p. 807
1975Equus (Parastilidequus) parastylidens Mooser and Dalquest p. 807
1980Equus Kurten and Anderson p. 285
1980Equus parastylidens Kurten and Anderson p. 287
1981Equus Thurmond and Jones p. 185
1988Equus Carroll
1989Equus Prothero and Schoch p. 532
1992Equus Koufos
1995Equus Capasso Barbato and Gliozzi p. 246
1995Equus leidyi Hulbert, Jr.
1995Equus Kelly p. 19
1996Equus Prado and Alberdi p. 676
1998Equus MacFadden p. 552
2004Equus (Amerhippus) Zurita et al.
2005Equus Cisneros p. 249
2005Equus Wilson and Reeder
2006Equus (Amerhippus) Rincón et al.
2006Equus Salles et al. p. 8
2014Equus Alberdi et al.
2017Haringtonhippus Heintzman et al. p. 5
2018Equus Eshelman et al. p. 8

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda
Reptiliomorpha
Anthracosauria
subclassAmphibiosauriaKuhn 1967
Cotylosauria()
Amniota
subclassSynapsida
Therapsida()
infraorderCynodontia()
Mammaliamorpha
Mammaliaformes
RankNameAuthor
classMammalia
Theriamorpha(Rowe 1993)
Theriiformes()
Trechnotheria
Cladotheria
Zatheria
subclassTribosphenida()
subclassTheria
Eutheria()
Placentalia
Boreoeutheria
Laurasiatheria
Scrotifera
Euungulata
Panperissodactyla
superorderPerissodactylamorpha
orderPerissodactyla()
superfamilyEquoidea
familyEquidae
subfamilyEquinae
tribeEquini
genusEquus

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

G. Equus Linnaeus 1758 [horse]
show all | hide all
Subg. Equus (Hemionus) Stehlin and Graziosi 1935
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Equus (Hemionus) hemionus Pallas 1775 [onager]
Subg. †Equus (Hesperohippus) Hibbard 1955
+
+
Invalid names: Equus midlandensis Quinn 1957 [synonym], Onager oviedoi Mooser 1959 [synonym]
Subg. †Equus (Sussemionus) Eisenmann 2010
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Equus africanus Heuglin and Fitzinger 1866 [African wild ass]
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Equus africanus africanus Heuglin and Fitzinger 1866 [Nubian wild ass]
Equus africanus somaliensis Noack 1884 [Somali wild ass]
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Invalid names: Equus africanus somalicus Sclater 1884 [synonym]
Invalid names: Asinus asinus dianae Dollman 1935 [synonym]
Equus alaskae Winans 1989
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Invalid names: Equus lambei Hay 1917 [synonym]
Equus asinus Linnaeus 1758 [donkey]
Equus australis Moreno 1888
Equus caballus Linnaeus 1758 [horse]
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Equus caballus ferus Boddaert 1785
Invalid names: Equus (Amerhippus) neogeus Lund 1840 [synonym], Equus hippagrus Smith 1841 [synonym]
Equus calobatus Troxell 1915
Equus capensis Broom 1909
Equus cedralensis Alberdi et al. 2014
Equus coliemensis Lazarev 1980
Equus complicatus Leidy 1858
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Invalid names: Equus americanus Leidy 1847 [replaced], Equus eous Cope 1895 [synonym], Equus major DeKay 1842 [synonym]
Equus conversidens Owen 1869
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Invalid names: Equus barcenaei Cope 1884 [synonym], Onager zoyatalis Mooser 1959 [synonym]
Equus eisenmannae Qiu et al. 2004
Equus excelsus Leidy 1858
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Invalid names: Asinus aguascalentensis Mooser 1959 [synonym], Onager arellanoi Mooser 1959 [synonym], Onager hibbardi Mooser 1959 [synonym]
Equus francisci Hay 1915
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Invalid names: Equus (Asinus) calobatus Troxell 1915 [synonym], Equus arrelanoi Mooser 1958 [synonym], Equus quinni Slaughter et al. 1962 [synonym]
Equus fraternus Leidy 1858
Equus fromanius Repenning et al. 1995
Equus giganteus Gidley 1901
Equus holmesi Hay 1920
Equus intermedius Cope 1895
Equus jubatus Hay 1927
Equus laurentius Hay 1913
Equus mexicanus Hibbard 1955
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Invalid names: Equus occidentalis Leidy 1865 [synonym], Equus pacificus Leidy 1868 [synonym], Equus scotti Gidley 1900 [synonym]
Equus nalaikhaensis Kuznetsova and Zhegallo 1996
Equus nearcticus Blake 1863
Equus nevadanus Hay 1927
Equus niobrarensis Hay 1913
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Invalid names: Equus hatcheri Hay 1915 [synonym]
Equus nobisi Pichardo 2004
Equus pectinatus Cope 1901
Equus przewalskii Poliakov 1881 [Przewalski's horse]
Equus pseudaltidens Hulbert, Jr. 1995
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Invalid names: Onager altidens Quinn 1957 [replaced]
Equus quagga Boddaert 1785 [plains zebra]
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Equus quagga boehmi Matschie 1892
Equus quagga borensis Lönnberg 1922
Equus quagga burchelli Gray 1824 [Burchell's zebra]
Equus quagga crawshayi De Winton 1896
Equus quagga quagga Boddaert 1785
Equus sanmeniensis Teilhard de Chardin and Piveteau 1930
Equus santaeelenae Spillmann 1938
Equus sivalensis Falconer and Cautley 1849
Equus tabeti Arambourg 1970
Equus yunnanensis Colbert 1940
Equus zebra Linnaeus 1758 [mountain zebra]
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Equus zebra hartmannae Matschie 1898 [Hartmann's mountain zebra]
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Invalid names: Equus matschiei Zukowsky 1924 [synonym], Equus penricei Thomas 1900 [synonym]
Equus zebra zebra Linnaeus 1758 [Cape mountain zebra]
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Invalid names: Equus campestris Gray 1852 [synonym], Equus indica Trouessart 1898 [synonym], Equus montanus Burchell 1822 [synonym], Equus zebra frederici Trouessart 1905 [synonym]
Invalid names: Allozebra Trumler 1961 [synonym], Asinus Gray 1822 [synonym], Asinus africanus aegyptiacus Heuglin and Fitzinger 1866 [synonym], Dolichohippus Heller 1912 [synonym], Equus (Amerhippus) Hoffstetter 1950 [invalid subgroup], Equus (Parastilidequus) Mooser and Dalquest 1975 [invalid subgroup], Equus asinus aethiopicus Denman 1957 [synonym], Equus leidyi Hay 1913 [nomen vanum], Equus parastylidens Mooser 1959 [nomen dubium], Equus semiplicatus Cope 1893 [nomen dubium], Equus taeniopus Heuglin 1861 [nomen dubium], Haringtonhippus Heintzman et al. 2017 [synonym], Hippotherium princeps Leidy 1890 [nomen dubium], Hippotigris Hamilton-Smith 1841 [synonym], Kolpohippus van Hoepen 1930 [synonym], Kraterohippus van Hoepen 1930 [synonym], Neohippus Abel 1913 [synonym], Onager Brisson 1762 [synonym], Sterrohippus van Hopen 1930 [synonym], Tomolabis Cope 1892 [synonym]
Diagnosis
ReferenceDiagnosis
J. H. Quinn 1955Large horses with complex permanent upper cheek teeth; styles of ectoloph high and thick, valleys deep and concave; protocones elongate and trans- versely compressed, internally concave but not as markedly as in Asinus; lower per- manent teeth with long, crescentic meta- conids and metastylids, intervening valleys U-shaped; lower molars with short median valleys not penetrating between the reen- trants of the flexids as deeply as in Hippo- tigris. In Old World species the median valley reaches the reentrants of the flexids but does not penetrate as deeply as in Hip- potigris; lower milk dentition without parastylids and hypostylids.
J. H. Quinn 1955 (Asinus)Lower milk dentition with parastylids and hypostylids weak or absent; lower permanent dentition with anterior border of metaflexid produced outward in a deep sharp angle exceeding either Equus or Hippotigris; metaconid directed inward and then forward, elongate and flattened internally, metastylid deflected, restricted, and rounded, inter- vening valley V-shaped as in the zebras but less deeply so; entoconid rounded and restricted; hylpoconulid prominent and with a hypostylid; pli caballinid present; median valley of molars variably shortened and not protruding beyond the reentrants of the flexids which form a short narrow commissure; upper permanent teeth with small fossettes; small enamel inflections; protocones excessively flat- tened and concave internally in late
species; metapodials slender.
J. H. Quinn 1957 (Asinus)Upper permanent teeth with square outline, small fossettes, protocones shorter than in Onager and teeth less hypsodont; lower permanent dentition, metaconid tends to be deflected inward, then forward, metastylid deflected and short tending to be nearly rounded; inter- vening valley V-shaped as in Hippotigris but less deeply so, no parastylid, pli caballinid present, hypoconulid prominent and with a hypostylid, median valley of molars not protruding between re-entrants of the flexids (except in very early stage of wear); lower milk dentition with parastylids and hypostylids weak or absent; metatarsals short and stout but less so than in Equus
J. H. Quinn 1957 (Onager)Size range equal to Equus; pattern of upper cheek teeth more complex, protocones elongated, hypoconal groove of premolars tends to be partly closed, third molar less modified than in Equus or Asinus; lower molars with median valley shorter than in most species of Equus; upper and lower teeth equalling or sur- passing Equus in hypsodonty and appreciably more hypsodont than Asinus; metapodials long and more slender than in Equus, longer and more slender than in A sinus.
P. D. Heintzman et al. 2017 (Haringtonhippus)Haringtonhippus is the sister genus to Equus (equid crown group), with Hippidion being sister to the Haringtonhippus-Equus clade (Figure 1). Haringtonhippus can be differentiated from Equus and Hip- pidion by 178 synapomorphic positions in the mitochondrial genome, including four insertions and 174 substitutions (Appendix 1—Table 2 and Appendix 1—table 2—source data 1). We caution that these synapomorphies are tentative and will likely be reduced in number as a greater diversity of mitochondrial genomes for extinct equids become available.