Editing Zebra (section)

==Taxonomy==
{{Further|Evolution of the horse}}
Zebras are classified in the genus ''[[Equus (genus)|Equus]]'' (known as equines) along with [[wild horse|horses]] and [[Asinus|asses]]. These three groups are the only living members of the family [[Equidae]].<ref name="MacDonald" /> The [[plains zebra]] and [[mountain zebra]] were traditionally placed in the [[subgenus]] ''Hippotigris'' (C. H. Smith, 1841) in contrast to the [[Grévy's zebra]] which was considered the sole species of subgenus ''Dolichohippus'' (Heller, 1912).<ref name="Prothero 2003">{{Cite book |title=Horns, Tusks, and Flippers: The Evolution of Hoofed Mammals |last1=Prothero |first1=D. R. |last2=Schoch|first2= R. M. |url=https://books.google.com/books?id=kWpQX-sfsLgC&q=Horns,+Tusks,+and+Flippers:+The+Evolution+of+Hoofed+Mammals |publisher=[[Johns Hopkins University Press]] |pages=216–218 |year=2003 |isbn=978-0-8018-7135-1}}</ref><ref>{{cite web|title=Hippotigris|website=ITIS|url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=926069#null|access-date=31 August 2020}}</ref><ref>{{cite web|title=Dolichohippus|website=ITIS|url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=926067#null|access-date=31 August 2020}}</ref> Groves and Bell (2004) placed all three species in the subgenus ''Hippotigris''.<ref name="GrovesBell2004">{{cite journal |author=Groves|first1= C. P. |last2=Bell|first2= C. H. |year=2004 |title=New investigations on the taxonomy of the zebras genus ''Equus'', subgenus ''Hippotigris'' |journal=Mammalian Biology |volume=69 |issue=3 |pages=182–196 |doi=10.1078/1616-5047-00133|bibcode= 2004MamBi..69..182G }}</ref> A 2013 [[phylogenetic]] study found that the plains zebra is more closely related to Grévy's zebras than mountain zebras.<ref name="Vilstrup">{{cite journal |author=Vilstrup|first1= Julia T. |last2=Seguin-Orlando|first2= A. |last3=Stiller|first3= M. |last4=Ginolhac|first4= A. |last5=Raghavan|first5= M. |last6=Nielsen|first6= S. C. A. |year=2013 |title=Mitochondrial phylogenomics of modern and ancient equids |journal=[[PLoS One]] |volume=8 |issue=2 |page=e55950 |doi=10.1371/journal.pone.0055950 |display-authors=etal |pmid=23437078 |pmc=3577844|bibcode= 2013PLoSO...855950V |doi-access= free }}</ref> The extinct [[quagga]] was originally classified as a distinct species.<ref>{{cite book |last1=Groves|first1= C. |last2=Grubb|first2= P. |year=2011 |title=Ungulate Taxonomy |publisher=Johns Hopkins University Press |page=16 |isbn=978-1-4214-0093-8}}</ref> Later genetic studies have placed it as the same species as the plains zebra, either a subspecies or just the southernmost population.<ref name="smithsonian">{{Cite journal |last1=Hofreiter |first1=M. |last2=Caccone |first2=A. |last3=Fleischer |first3=R. C. |last4=Glaberman |first4=S. |last5=Rohland |first5=N. |last6=Leonard |first6=J. A. |doi=10.1098/rsbl.2005.0323 |title=A rapid loss of stripes: The evolutionary history of the extinct quagga |journal=[[Biology Letters]] |volume=1 |issue=3 |pages=291–295 |year=2005 |pmid=17148190 |pmc=1617154}}</ref><ref name="PedersenAlbrechtsen2018">{{cite journal |last1=Pedersen |first1=Casper-Emil T. |last2=Albrechtsen |first2=Anders |last3=Etter |first3=Paul D. |last4=Johnson |first4=Eric A. |last5=Orlando |first5=Ludovic |last6=Chikhi |first6=Lounes |last7=Siegismund |first7=Hans R. |last8=Heller |first8=Rasmus |year=2018|title=A southern African origin and cryptic structure in the highly mobile plains zebra |journal=[[Nature Ecology & Evolution]] |volume=2 |issue=3 |pages=491–498 |issn=2397-334X |doi=10.1038/s41559-017-0453-7 |pmid=29358610|bibcode=2018NatEE...2..491P |s2cid=3333849 }}</ref> Molecular evidence supports zebras as a [[monophyletic]] [[Lineage (evolution)|lineage]].<ref name="Vilstrup" /><ref name="Forstén">{{cite journal |author=Forstén|first= Ann |year=1992 |title=Mitochondrial-DNA timetable and the evolution of ''Equus'': of molecular and paleontological evidence |journal=Annales Zoologici Fennici |volume=28 |pages=301–309 |url=http://www.sekj.org/PDF/anzf28/anz28-301-309.pdf}}</ref><ref>{{cite journal |last1=Ryder |first1=O. A. |last2=George |first2=M. |year=1986 |title=Mitochondrial DNA evolution in the genus ''Equus'' |journal=[[Molecular Biology and Evolution]] |volume=3 |issue=6 |pages=535–546 |doi=10.1093/oxfordjournals.molbev.a040414 |pmid=2832696 |url=http://mbe.library.arizona.edu/data/1986/0306/5geor.pdf |doi-access=free |access-date=13 November 2015 |archive-date=28 May 2016 |archive-url=https://web.archive.org/web/20160528170756/http://mbe.library.arizona.edu/data/1986/0306/5geor.pdf |url-status=dead }}</ref>

''Equus'' originated in North America and direct [[paleogenomics|paleogenomic]] sequencing of a 700,000-year-old middle Pleistocene horse [[metapodial]] bone from Canada implies a date of 4.07 million years ago (mya) for the most [[recent common ancestor]] of the equines within a range of 4.0 to 4.5 mya.<ref name="ReferenceA">{{cite journal |last1=Orlando|first1= L.|last2 =Ginolhac|first2= A.|last3= Zhang|first3= G.|last4= Froese|first4= D.|last5= Albrechtsen|first5= A.|last6= Stiller|first6= M.|display-authors= etal |title=Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse |journal=[[Nature (journal)|Nature]] |volume=499 |issue=7456 |pages=74–78 |date=July 2013 |pmid=23803765 |doi=10.1038/nature12323|bibcode= 2013Natur.499...74O|s2cid= 4318227}}</ref> Horses [[Split (phylogenetics)|split]] from asses and zebras around this time and equines colonised Eurasia and Africa around 2.1–3.4 mya. Zebras and asses diverged from each other close to 2 mya. The mountain zebra diverged from the other species around 1.6 mya and the plains and Grévy's zebra split 1.4 mya.<ref name=Jónsson2014>{{cite journal|last1=Jónsson|first1=Hákon|last2=Schubert|first2=Mikkel|last3=Seguin-Orlando|first3=Andaine|last4=Orlando|first4=Ludovic|year=2014|title=Speciation with gene flow in equids despite extensive chromosomal plasticity|journal=Proceedings of the National Academy of Sciences|volume=111|issue=52|pages=18655–18660|doi=10.1073/pnas.1412627111 |pmid=25453089 |pmc=4284605 |bibcode=2014PNAS..11118655J |doi-access=free}}</ref>

A 2017 mitochondrial DNA study placed the Eurasian ''[[Equus ovodovi]]'' and the subgenus ''Sussemionus'' lineage as closer to zebras than to asses.<ref>{{Cite journal |last1=Druzhkova |first1=Anna S. |last2=Makunin |first2=Alexey I. |last3=Vorobieva |first3=Nadezhda V. |last4=Vasiliev |first4=Sergey K. |last5=Ovodov |first5=Nikolai D. |last6=Shunkov |first6=Mikhail V. |last7=Trifonov |first7=Vladimir A. |last8=Graphodatsky |first8=Alexander S. |date=January 2017 |title=Complete mitochondrial genome of an extinct ''Equus (Sussemionus) ovodovi'' specimen from Denisova cave (Altai, Russia) |journal=Mitochondrial DNA Part B |language=en |volume=2 |issue=1 |pages=79–81 |doi=10.1080/23802359.2017.1285209 |pmid=33473722 |pmc=7800821 |issn=2380-2359 |doi-access=free}}</ref> However, other studies disputed this placement, finding the ''Sussemionus'' lineage basal to the zebra+asses group, but suggested that the ''Sussemionus'' lineage may have received gene flow from zebras.<ref>{{Cite journal |last1=Cai |first1=Dawei |last2=Zhu |first2=Siqi |last3=Gong |first3=Mian |last4=Zhang |first4=Naifan |last5=Wen |first5=Jia |last6=Liang |first6=Qiyao |last7=Sun |first7=Weilu |last8=Shao |first8=Xinyue |last9=Guo |first9=Yaqi |last10=Cai |first10=Yudong |last11=Zheng |first11=Zhuqing |last12=Zhang |first12=Wei |last13=Hu |first13=Songmei |last14=Wang |first14=Xiaoyang |last15=Tian |first15=He |date=2022-05-11 |title=Radiocarbon and genomic evidence for the survival of Equus Sussemionus until the late Holocene |journal=eLife |language=en |volume=11 |doi=10.7554/eLife.73346 |issn=2050-084X |pmc=9142152 |pmid=35543411 |doi-access=free }}</ref>

[[File:Equus quagga quagga, coloured.jpg|thumb|alt=Photograph of a Quagga mare |[[Quagga]] mare at London Zoo, 1870, the only specimen photographed alive. This animal was historically considered a separate species but is now considered a subspecies or population of plains zebra.]]
The cladogram of ''Equus'' below is based on Vilstrup and colleagues (2013) and Jónsson and colleagues (2014):<ref name="Vilstrup" /><ref name=Jónsson2014/>
{{clade| style=font-size:85%; line-height:90%;
|label1=''Equus''
|1={{clade
 |1={{clade
|label2=
  |1={{clade
 |label1='''Zebras'''
 |label2=[[Asinus|Wild asses]]
   |1={{clade
    |1=[[Mountain zebra]] (''E. zebra'') [[File:The book of the animal kingdom (Plate XVII) (white background).jpg|40 px]]
    |2={{clade
     |1=[[Plains zebra]] (''E. quagga'') [[File:NIE 1905 Horse - Burchell's zebra.jpg|40 px]]
     |2=[[Grévy's zebra]] (''E. grevyi'') [[File:Equus grevyi (white background).png|40 px]]}} }}
   |2={{clade
    |1={{clade
     |1=[[Kiang]] (''E. kiang'')  [[File:Equus hemionus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|40 px]]
     |2=[[Onager]] (''E. hemionus'') [[File:Hémippe (white background).jpg|40 px]]}}
    |2=[[African wild ass]] (''E. africanus'') [[File:Âne d'Ethiopie (white background).jpg|40 px]]}} }} }}
  |label2=[[Wild horse|Horses]]
 |2={{clade
    |1=[[Horse]] (''E. ferus caballus'') [[File:NIEdot332 white background 2.jpg|40 px]]
    |2=[[Przewalski's horse]] (''E. ferus przewalski'') [[File:The Soviet Union 1959 CPA 2325 stamp (Przewalski's Horse) white background.jpg|40 px]]}} }} }}

===Extant species===
{| class="wikitable"
|+ style="text-align: centre;" |
! Name
! Dimensions
! Description
! Distribution
! Subspecies
! Chromosomes
! Image
|-
| [[Grévy's zebra]] (''Equus grevyi'')
|'''Body length''': {{cvt|250|–|300|cm}}<br>'''Tail length''': {{cvt|38|–|75|cm}}<br>'''Shoulder height''': {{cvt|125|–|160|cm}}<br>'''Weight''': {{cvt|352|–|450|kg}}.{{sfn|Caro|2016|p=9}}
|Thin, elongated skull, robust neck and conical ears; narrow striping pattern with [[Concentric objects|concentric]] rump stripes, white belly and tail base and white line around the ashy muzzle.<ref name="MacDonald">{{Cite book |last=Rubenstein|first= D. I. |contribution=Horse, Zebras and Asses |year=2001 |title=The Encyclopedia of Mammals |edition=2nd |editor=MacDonald|editor-first= D. W. |publisher=[[Oxford University Press]] |pages=468–473 |isbn=978-0-7607-1969-5}}</ref><ref name="Churcher 1993" />{{sfn|Caro|2016|p=15}}
| [[East Africa|Eastern Africa]] including [[Horn of Africa|the Horn]];<ref name="Churcher 1993">{{cite journal |author=Churcher|first= C. S. |year=1993 |title=Equus grevyi |url=http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-3519-453-01-0001.pdf |journal=[[Mammalian Species]] |issue=453 |pages=1–9 |doi=10.2307/3504222 |jstor=3504222}}</ref> arid and semiarid [[grassland]]s and [[shrubland]]s.{{sfn|Caro|2016|p=14}}
|[[Monotypic taxon|Monotypic]]<ref name="Churcher 1993"/>
|46{{sfn|Caro|2016|p=14}}
|[[File:Grevy's Zebra Stallion.jpg|120px]]
|-
|[[Plains zebra]] (''Equus quagga'')
|'''Body length''': {{cvt|217|–|246|cm}}<br>'''Tail length''': {{cvt|47|–|56|cm|in}}<br>'''Shoulder height''': {{cvt|110|–|145|cm}}<br>'''Weight''': {{cvt|175|–|385|kg}}.{{sfn|Caro|2016|p=9}}
|Thick bodied with relatively short legs and an obtusely-shaped skull profile with a protruding forehead and a more recessed nose area;<ref name="MacDonald" /><ref name="Grub 1981">{{cite journal |last1=Grubb |first1=P. |year=1981 |title=Equus burchellii |journal=Mammalian Species |issue=157 |pages=1–9 |doi=10.2307/3503962 |jstor=3503962|doi-access=free }}</ref> broad stripes, horizontal on the rump, with northern populations having more extensive striping while populations further south have whiter legs and bellies and more brown "shadow" stripes while the snout is black.<ref name="MacDonald" /><ref name="Estes 1991" />{{sfn|Caro|2016|pp=12–13}}<ref name="Skinner"/>
|Eastern and [[southern Africa]]; [[savannah]]s, grasslands and open woodlands.{{sfn|Caro|2016|p=11}}
|6<ref name="GrovesBell2004"/> or monotypic<ref name="PedersenAlbrechtsen2018"/>
|44{{sfn|Caro|2016|p=13}}
|[[File:Equus quagga burchellii - Etosha, 2014.jpg|120px]]
|-
|[[Mountain zebra]] (''Equus zebra'')
|'''Body length''': {{cvt|210|–|260|cm}}<br>'''Tail length''': {{cvt|40|–|55|cm}}<br>'''Shoulder height''': {{cvt|116|–|146|cm}}<br>'''Weight''': {{cvt|204|–|430|kg}}.{{sfn|Caro|2016|p=9}}
|[[Eye sockets]] more circular and positioned farther back, a squarer [[Nuchal lines|nuchal crest]], [[dewlap]] present under neck and compact hooves; stripes intermediate in width between the other species, with gridiron and horizontal stripes on the rump, while the belly is white and the black muzzle is lined with [[Chestnut (color)|chestnut]] or orange.<ref name="Penzhorn 1988">{{cite journal |last1=Penzhorn |first1=B. L. |year=1988 |title=Equus zebra |journal=Mammalian Species |issue=314 |pages=1–7 |doi=10.2307/3504156|jstor=3504156 |s2cid=253987177 }}</ref><ref name="MacDonald" /><ref name="handbook" />{{sfn|Caro|2016|p=14}}
|Southwestern Africa; mountains, rocky uplands and [[Karoo]] shrubland.{{sfn|Caro|2016|p=11}}<ref name="Penzhorn 1988" /><ref name="Skinner"/>
|2<ref name="Penzhorn 1988" />
|32{{sfn|Caro|2016|p=14}}
|[[File:Equus zebra hartmannae - Etosha 2015.jpg|120px]]
|}

===Fossil record===
[[File:Equus mauritanicus.JPG|thumb|right|alt= A fossil skull of ''Equus mauritanicu'' | Fossil skull of ''Equus mauritanicus'']]
In addition to the three living species, some fossil zebras and relatives have also been identified. ''E. oldowayensis'' is identified from remains in Olduvai Gorge dating to 1.8 mya.<ref name="Churcher2006" /> Fossil skulls of ''E. mauritanicus'' from Algeria which date to around 1 mya appears to show affinities with the plains zebra.<ref name="Azzaroli">{{Cite journal |last1=Azzaroli |first1=A. |last2=Stanyon |first2=R. |doi=10.1007/BF03001000 |title=Specific identity and taxonomic position of the extinct Quagga |journal=Rendiconti Lincei |volume=2 |issue=4 |page=425 |year=1991 |s2cid=87344101 }}</ref><ref>{{cite journal|author=Eisenmann|first= V.|year=2008|title=Pliocene and Pleistocene equids: palaeontology versus molecular biology|journal= Courier Forschungsinstitut Senckenberg|volume=256|pages=71–89|url=https://www.researchgate.net/publication/281338907}}</ref> ''[[Equus capensis|E. capensis]]'', known as the Cape zebra, appeared around 2 mya and lived throughout southern and eastern Africa.<ref name="Badenhorst2019">{{cite journal |author=Badenhorst|first1= S. |last2=Steininger|first2= C. M. |year=2019 |title=The Equidae from Cooper's D, an early Pleistocene fossil locality in Gauteng, South Africa |journal=[[PeerJ]] |volume=7 |pages= e6909 |doi=10.7717/peerj.6909 |pmid= 31143541 |pmc= 6525595 |doi-access=free}}</ref><ref name="Churcher2006">{{cite journal |author=Churcher|first= C. S. |year=2006 |title=Distribution and history of the Cape zebra (''Equus capensis'') in the Quarternary of Africa |journal=[[Transactions of the Royal Society of South Africa]] |volume=61 |issue=2 |pages=89–95 |doi=10.1080/00359190609519957|bibcode= 2006TRSSA..61...89C |s2cid= 84203907 }}</ref>
[[File:Grévy's × Plains Zebra, ol pejeta imported from iNaturalist photo 401473965 (cropped).jpg|thumb|Grévy's × plains zebra hybrid, alongside plains zebras.]]

===Hybridisation===
{{Main|Zebroid}}
Fertile hybrids have been reported in the wild between plains and Grévy's zebra.<ref>{{cite journal |first1=J. E.|last1= Cordingley |first2=S. R.|last2= Sundaresan |first3=I. R.|last3= Fischhoff |first4=B.|last4= Shapiro |first5=J.|last5= Ruskey |first6=D. I.|last6= Rubenstein |year=2009 |title=Is the endangered Grevy's zebra threatened by hybridization? |journal=Animal Conservation |volume=12 |issue=6 |pages=505–513 |doi=10.1111/j.1469-1795.2009.00294.x|bibcode= 2009AnCon..12..505C |s2cid= 18388598 }}</ref> Hybridisation has also been recorded between the plains and mountain zebra, though it is possible that these are infertile due to the difference in chromosome numbers between the two species.<ref>{{cite book |author=Giel|first1= E.-M. |last2=Bar-David|first2= S. |last3=Beja-Pereira|first3= A. |last4=Cothern|first4= E. G. |last5=Giulotto|first5= E. |last6=Hrabar|first6= H. |last7=Oyunsuren|first7= T. |last8=Pruvost|first8= M. |year=2016 |contribution=Genetics and Paleogenetics of Equids |title=Wild Equids: Ecology, Management, and Conservation |editor=Ransom|editor-first= J. I. |editor2=Kaczensky|editor-first2=P. |publisher=Johns Hopkins University Press |page=99 |isbn=978-1-4214-1909-1}}</ref> Captive zebras have been bred with horses and [[donkeys]]; these are known as [[zebroids]]. A zorse is a cross between a zebra and a horse; a zonkey, between a zebra and a donkey; and a zoni, between a zebra and a [[pony]]. Zebroids are often born sterile with [[dwarfism]].<ref>{{cite web |author=Bittel|first= Jason |date=19 June 2015 |title=Hold Your Zorses: The sad truth about animal hybrids |publisher=[[Slate.com]] |access-date=16 May 2020 |url=https://slate.com/technology/2015/06/zonkeys-ligers-the-sad-truth-about-animal-hybrids.html}}</ref>