Equidae

Equidae Temporal range: 50.3–0  Ma PreꞒ Ꞓ O S D C P T J K Pg N Early Eocene - Recent[1]
Persian onager
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Suborder:	Hippomorpha
Family:	Equidae Gray, 1821
Subfamilies
†Anchitheriinae Equinae

Equidae (sometimes known as the horse family) is the

The term equid refers to any member of this family, including any equine.

The oldest known fossils assigned to Equidae were found in North America, and date from the early Eocene epoch, 54 million years ago. They were once assigned to the genus Hyracotherium, but the type species of that genus is now regarded as a palaeothere. The other species have been split off into different genera. These early equids were fox-sized animals with three toes on the hind feet, and four on the front feet. They were herbivorous browsers on relatively soft plants, and already adapted for running. The complexity of their brains suggest that they already were alert and intelligent animals.^[2] Later species reduced the number of toes, and developed teeth more suited for grinding up grasses and other tough plant food.

The equids, like other perissodactyls, are hindgut fermenters. They have evolved specialized teeth that cut and shear tough plant matter to accommodate their fibrous diet.^[3] Their seemingly inefficient digestion strategy is a result of their size at the time of its evolution,^[4] as they would have already had to be relatively large mammals to be supported on such a strategy.

The family became relatively diverse during the Miocene epoch,^[5] with many new species appearing. By this time, equids were more truly horse like, having developed the typical body shape of the modern animals.^[6] Many of these species bore the main weight of their bodies on their central third toe, with the others becoming reduced and barely touching the ground, if at all. The sole surviving genus, Equus, had evolved by the early Pleistocene epoch, and spread rapidly through the world.^[7]

• Order Perissodactyla (In addition to Equidae, Perissodactyla includes four species of tapir in a single genus, as well as five living species (belonging to four genera) of rhinoceros.) † indicates extinct taxa.
  • Family Equidae
    • Subfamily †Eohippinae?
      • Genus †Epihippus
      • Genus †Haplohippus
      • Genus †Eohippus
      • Genus †Minippus^[8]
    • Subfamily †Propalaeotheriinae?
      • Genus †Orohippus
      • Genus †Pliolophus
      • Genus †Protorohippus
      • Genus †Sifrhippus
      • Genus †Xenicohippus^[8]
      • Genus †Eurohippus
      • Genus †Propalaeotherium?^[9]
    • Subfamily †Anchitheriinae
      • Genus †Anchitherium
      • Genus †Archaeohippus
      • Genus †Desmatippus
      • Genus †Hypohippus
      • Genus †Kalobatippus
      • Genus †Megahippus
      • Genus †Mesohippus
      • Genus †Miohippus
      • Genus †Parahippus
      • Genus †Sinohippus
    • Subfamily Equinae
      • Genus †Merychippus
      • Genus †Scaphohippus
      • Genus †Acritohippus
      • Tribe †Hipparionini
        • Genus †Eurygnathohippus
        • Genus †Hipparion
        • Genus †Hippotherium
        • Genus †Nannippus
        • Genus †Neohipparion
        • Genus †Proboscidipparion
        • Genus †Pseudhipparion
      • Tribe Equini
        • Genus †Haringtonhippus^[10]
        • Genus †Heteropliohippus^[11]
        • Genus †Parapliohippus^[11]
        • Subtribe
          Protohippina
          • Genus †Calippus
          • Genus †Protohippus
        • Subtribe
          Equina
          • Genus †Astrohippus
          • Genus †Dinohippus
          • Genus
            extant
            )
            • Equus ferus Wild horse
              • Equus ferus caballus
                Domestic horse
              • †Equus ferus ferus Tarpan
              • Equus ferus przewalskii Przewalski's horse
            • †Equus algericus^[12]
            • †Equus alaskae
            • †Equus lambei Yukon wild horse
            • †Equus niobrarensis
            • †Equus scotti
            • †Equus conversidens Mexican horse
            • †Equus semiplicatus
            • Subgenus †
              Amerhippus (this subgenus and its species are possibly synonymous with E. ferus)^[13]
              • †
                Equus andium
              • †Equus neogeus
              • †Equus insulatus
            • Subgenus Asinus
              • Equus africanus African wild ass
                • Equus africanus africanus Nubian wild ass
                • Equus africanus asinus Domestic donkey
                • †Equus africanus atlanticus Atlas wild ass
                • Equus africanus somalicus Somali wild ass
              • Equus hemionus Onager or Asiatic wild ass
                • Equus hemionus hemionus Mongolian wild ass
                • †Equus hemionus hemippus Syrian wild ass
                • Equus hemionus khur Indian wild ass
                • Equus hemionus kulan Turkmenian kulan
                • Equus hemionus onager Persian onager
              • Equus kiang Kiang
                • Equus kiang chu
                  Northern kiang
                • Equus kiang kiang
                  Western kiang
                • Equus kiang holdereri
                  Eastern kiang
                • Equus kiang polyodon
                  Southern kiang
              • †Equus hydruntinus
                European ass
              • †Equus altidens
              • †Equus tabeti
              • †Equus melkiensis
              • †Equus graziosii
            • Subgenus
              Hippotigris^[a]
              • Equus grevyi Grévy's zebra
              • †Equus koobiforensis
              • †Equus oldowayensis
              • Equus quagga Plains zebra
                • Equus quagga boehmi Grant's zebra
                • Equus quagga borensis Maneless zebra
                • Equus quagga burchellii Burchell's zebra
                • Equus quagga chapmani Chapman's zebra
                • Equus quagga crawshayi Crawshay's zebra
                • †Equus quagga quagga Quagga
                • Equus quagga selousi Selous' zebra
              • Equus zebra Mountain zebra
                • Equus zebra hartmannae Hartmann's mountain zebra
                • Equus zebra zebra Cape mountain zebra
              • †Equus capensis
              • †Equus mauritanicus
            • Subgenus †Parastylidequus
              • †Equus parastylidens Mooser's horse
            • †Subgenus Sussemionus^[16]
              • †Equus ovodovi^[17]
            • incertae sedis
              • †Equus simplicidens Hagerman horse
              • †Equus cumminsii
              • †Equus livenzovensis
              • †Equus sanmeniensis
              • †Equus teilhardi
              • †Equus numidicus
              • †Equus plicidens
              • †Equus cedralensis
              • †Equus stenonis group
                • †Equus stenonis Stenon zebra
                  • †Equus stenonis guthi
                  • †Equus stenonis senezensis
                  • †Equus stenonis pamirensis (Hippotigris pamirensis)
                  • †Equus stenonis petraloniensis
                  • †Equus stenonis vireti
                • †Equus sivalensis
                • †Equus stehlini
                • †Equus sussenbornensis
                • †Equus verae
                • †Equus namadicus
              • †subgenus Allozebra
                • †Equus (A.) occidentalis western horse
          • †Equus (A.) excelsus
            • • †subgenus Hesperohippus
                • †Equus (H.) pacificus
                • †Equus (H.) mexicanus
              • †Equus complicatus
              • †Equus fraternus^[18]
              • †Equus major
              • †Equus giganteus
              • †Equus pectinatus
              • †Equus crenidens
          • Genus †Hippidion
          • Genus †
            Onohippidium
          • Genus †Pliohippus

Notes

1. ^ Although the plains and mountain zebras have been placed in Hippotigris and Grévy's zebra in Dolichohippus, Vilstrup et al. (2013) finds that the plains zebra and Grévy's zebra are more closely related.^[14] Groves and Bell (2004) place all three species in the subgenus Hippotigris.^[15]

References

1. ^ "PBDB". paleobiodb.org. Retrieved 2021-07-18.
2. ISBN 1-84028-152-9
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3. S2CID 133808650
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4. S2CID 5053639
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5. ISBN 978-3-031-27143-4
   – via www.springer.com.
6. S2CID 19876380
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7. ISBN 0-8160-1194-X
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8. ^
   doi:10.1046/j.1096-3642.2002.00005.x
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9. doi:10.18563/pv.40.2.e1
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10. doi:10.5479/si.00963801.48-2086.515
11. ^ ^{a b} Bravo-Cuevas, V.M.; Ferrusquía-Villafranca, I. (2010). "The oldest record of Equini (Mammalia: Equidae) from Mexico" (PDF). Revista Mexicana de Ciencias Geológicas. 27 (3): 593–603. Retrieved 14 August 2020.
12. doi:10.3406/quate.1999.1649
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13. S2CID 19069554
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14. PMID 23437078
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15. doi:10.1078/1616-5047-00133
    .
16. PMID 20338542
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17. S2CID 128625427
    .
18. ^ "Fossilworks: Equus fraternus". fossilworks.org. Retrieved 17 December 2021.

Look up Equidae or equid in Wiktionary, the free dictionary.