Equidae

2025-09-10T17:46:46Z

2605:59C0:20C0:3E08:7:8AD7:7B27:1C2A: Hyracotherium is not part of Equidae.

{{Short description|Family of hoofed mammals}}
{{Automatic taxobox
| name = Equidae
| fossil_range = {{Fossil range|55.8|0|earliest=Eocene}} [[Early Eocene]] - [[holocene|Recent]]<ref>{{Cite web|title=PBDB|url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=42984&is_real_user=1|access-date=2021-07-18|website=[[Paleobiology Database]]}}</ref><ref>{{Citation |last1=Secord |first1=Ross |last2=Bloch |first2=Jonathan I. |last3=Chester |first3=Stephen G. B. |last4=Boyer |first4=Doug M. |last5=Wood |first5=Aaron R. |last6=Wing |first6=Scott L. |last7=Kraus |first7=Mary J. |last8=McInerney |first8=Francesca A. |last9=Krigbaum |first9=John |year=2012 |title=Evolution of the Earliest Horses Driven by Climate Change in the Paleocene-Eocene Thermal Maximum |journal=Science |volume=335 |issue=6071 |page=959-962 |url=https://www.science.org/doi/10.1126/science.1213859 |doi= 10.1126/science.1213859|bibcode=2012Sci...335..959S |url-access=subscription }}</ref>
| image = Dubbo Zoo (3149120827).jpg
| image_caption = [[Persian onager]]
| taxon = Equidae
| authority = [[John Edward Gray|Gray]], 1821
| subdivision_ranks = Subfamilies
| subdivision = *{{extinct}}Eohippinae
*{{extinct}}[[Anchitheriinae]]
*[[Equinae]]
}}

'''Equidae''' (commonly known as the '''horse family''') is the [[Taxonomy (biology)|taxonomic]] [[Family (biology)|family]] of [[Wild horse|horse]]s and related animals, including [[Asinus|asses]], [[zebra|zebras]], and many extinct [[species]] known only from [[fossil]]s. The family evolved more than 50 million years ago, in the [[Eocene]] epoch, from a small, multi-toed [[ungulate]] into larger, single-toed animals. All [[Extant taxon|extant]] species are in the [[genus]] ''[[Equus (genus)|Equus]]'', which originated in North America. Equidae belongs to the order [[Perissodactyla]], which includes the extant [[tapir]]s and [[rhinoceros]], and several extinct families. It is more specifically grouped within the [[superfamily (taxonomy)|superfamily]] [[Equoidea]], the only other family being the extinct [[Palaeotheriidae]].

The term '''equid''' refers to any member of this family, including any [[equinae|equine]].

==Evolution==

{{main|Evolution of the horse}}
[[File:Extinct horses.jpg|thumb|left|Extinct equids restored to scale. Left to right: ''[[Mesohippus]]'', ''[[Neohipparion]]'', ''[[Eohippus]]'', ''[[Equus scotti]]'' and ''[[Hypohippus]]'']]

The oldest known [[fossil]]s 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 [[palaeotheriidae|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.<ref>{{cite book |editor=Palmer, D.|year=1999 |title= The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|publisher= Marshall Editions|location=London|pages= 255|isbn= 1-84028-152-9}}</ref> 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 fermentation|hindgut fermenters]]. They have evolved specialized teeth that cut and shear tough plant matter to accommodate their fibrous diet.<ref>{{Cite journal|last1=Engels|first1=Sandra|last2=Schultz|first2=Julia A.|date=June 2019|title=Evolution of the power stroke in early Equoidea (Perissodactyla, Mammalia)|journal=Palaeobiodiversity and Palaeoenvironments|language=en|volume=99|issue=2|pages=271–291|doi=10.1007/s12549-018-0341-4|bibcode=2019PdPe...99..271E |s2cid=133808650|issn=1867-1594}}</ref> Their seemingly inefficient digestion strategy is a result of their size at the time of its evolution,<ref>{{Cite journal|last=Janis|first=Christine|date=1976|title=The Evolutionary Strategy of the Equidae and the Origins of Rumen and Cecal Digestion|journal=Evolution|language=en|volume=30|issue=4|pages=757–774|doi=10.1111/j.1558-5646.1976.tb00957.x|pmid=28563331|s2cid=5053639|issn=1558-5646|doi-access=free}}</ref> 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,<ref>{{cite book |chapter-url=https://link.springer.com/chapter/10.1007/978-3-031-27144-1_2|chapter=Evolutionary Radiation of Equids|first1=Juan L.|last1=Cantalapiedra|first2=Oscar L.|last2=Sanisdro|first3=Enrique|last3=Cantero|first4=Jose Luis|last4=Prado|first5=Mª Teresa Luis|last5=Alberdi| editor1-first= Herbert H.| editor1-last=Prins | editor2-first= Ian J.| editor2-last= Gordon | date=4 August 2023|publisher=Springer|title=The Equids, A Suite of Splendid Species|series=Fascinating Life Sciences |pages=27–45|via=www.springer.com|doi=10.1007/978-3-031-27144-1_2|isbn=978-3-031-27143-4 }}</ref> with many new species appearing. By this time, equids were more truly horse like, having developed the typical body shape of the modern animals.<ref>{{Cite journal | last1 = MacFadden | first1 = B. J. | title = Fossil Horses--Evidence for Evolution | doi = 10.1126/science.1105458 | journal = Science | volume = 307 | issue = 5716 | pages = 1728–1730 | date = March 18, 2005 | pmid = 15774746| s2cid = 19876380 | url = http://doc.rero.ch/record/14414/files/PAL_E1597.pdf }}</ref> 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.<ref name=MamEv>{{cite book |author1=Savage, RJG |author2=Long, MR |name-list-style=amp |year=1986 |title=Mammal Evolution: an illustrated guide |publisher=Facts on File |location=New York |pages=[https://archive.org/details/mammalevolutioni0000sava/page/200 200–204] |isbn=0-8160-1194-X |url=https://archive.org/details/mammalevolutioni0000sava/page/200 }}</ref>
{{Clear}}

==Classification==
[[File:Equine evolution.jpg|thumb|Skeletons]]
[[File:F John Series 2 Protorohippus card 5.jpg|thumb|''Protorohippus'']]
[[File:Hipparion3.jpg|thumb|''Hipparion'']]
[[File:Przewalski horse.jpg|thumb|''Equus'' ([[Przewalski's Horse|Przewalski's horse]])]]
{{see also|List of perissodactyls}}

* '''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 [[Extinction|extinct]] taxa.
** Family '''Equidae'''
*** Subfamily †'''Eohippinae'''
**** Genus †''[[Epihippus]]''
**** Genus †''[[Haplohippus]]''
**** Genus †''[[Eohippus]]''
**** Genus †''[[Minippus]]''<ref name=Froehlich2002>{{cite journal |last1= Froehlich|first1= D.J. |date= February 2002 |title= Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla) |journal= Zoological Journal of the Linnean Society |volume= 134 |issue= 2 |pages= 141–256 |doi= 10.1046/j.1096-3642.2002.00005.x|doi-access= free }}</ref>
**** Genus †''[[Orohippus]]''
**** Genus †''[[Pliolophus]]''
**** Genus †''[[Protorohippus]]''
**** Genus †''[[Sifrhippus]]''
**** Genus †''[[Xenicohippus]]''<ref name=Froehlich2002/>
*** 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]]''<ref>Hay, Oliver P. (1915). "Contributions to the Knowledge of the Mammals of the Pleistocene of North America". Proceedings of the United States National Museum. 48 (2086): 535–549. {{doi|10.5479/si.00963801.48-2086.515}}</ref>
***** Genus †''[[Heteropliohippus]]''<ref name=Bravo2010>{{cite journal |last1= Bravo-Cuevas |first1= V.M. |last2= Ferrusquía-Villafranca |first2= I. |date= 2010 |title= The oldest record of Equini (Mammalia: Equidae) from Mexico |url= https://www.redalyc.org/pdf/572/57219891015.pdf |journal= Revista Mexicana de Ciencias Geológicas |volume= 27 |issue= 3 |pages= 593–603 |access-date= 14 August 2020}}</ref>
***** Genus †''[[Parapliohippus]]''<ref name=Bravo2010/>
***** Genus †''[[Calippus (mammal)|Calippus]]''
***** Genus †''[[Protohippus]]''
***** Genus †''[[Astrohippus]]''
***** Genus †''[[Dinohippus]]''
***** Genus ''[[Equus (genus)|Equus]]'' (22 species, 7 [[Extant taxon|extant]])
***** Genus †''[[Cremohipparion]]''
***** Genus †''[[Hippidion]]''
***** Genus †''[[Pliohippus]]''

==References==
{{Reflist}}
{{wiktionary|Equidae|equid}}
{{Perissodactyla}}
{{Perissodactyla Genera|P.}}
{{Equidae extinct nav|state=collapsed}}
{{Equus|state=collapsed}}
{{Taxonbar|from=Q165115}}
{{Authority control}}

[[Category:Equidae| ]]
[[Category:Extant Ypresian first appearances]]
[[Category:Mammal families]]
[[Category:Taxa named by John Edward Gray]]

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Equidae