Equidae

{{main|Evolution of the horse}}

File:Extinct horses.jpg, Neohipparion, Eohippus, Equus scotti and Hypohippus]]

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.{{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}} 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.{{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}} Their seemingly inefficient digestion strategy is a result of their size at the time of its evolution,{{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}} 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,{{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 }} with many new species appearing. By this time, equids were more truly horse like, having developed the typical body shape of the modern animals.{{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 }} 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.{{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 }}

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File:Equine evolution.jpg

File:F John Series 2 Protorohippus card 5.jpg

File:Hipparion3.jpg

File:Przewalski horse.jpg)]]

{{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 extinct taxa.
• Family Equidae
• Subfamily †Hyracotheriinae
• Genus †Epihippus
• Genus †Haplohippus
• Genus †Eohippus
• Genus †Minippus{{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 }}
• Genus †Orohippus
• Genus †Pliolophus
• Genus †Protorohippus
• Genus †Sifrhippus
• Genus †Xenicohippus
• 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 †HaringtonhippusHay, 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}}
• Genus †Heteropliohippus{{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}}
• Genus †Parapliohippus
• Genus †Calippus
• Genus †Protohippus
• Genus †Astrohippus
• Genus †Dinohippus
• Genus Equus (22 species, 7 extant)
• Genus †Cremohipparion
• Genus †Hippidion
• Genus †Pliohippus

{{Reflist}}

{{wiktionary|Equidae|equid}}

{{Perissodactyla}}

{{Perissodactyla Genera|P.}}

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{{Equus|state=collapsed}}

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Category:Extant Ypresian first appearances

Category:Mammal families

Category:Taxa named by John Edward Gray