Editing Perissodactyla (section)

===Prehistoric members===
[[File:Paleotherium magnum.jpg|thumb|Restoration of ''[[Palaeotherium]]'', a [[palaeothere]] genus first formally described in 1804]]
[[File:ChalicotheriumDB1.jpg|thumb|Live reconstruction of [[chalicothere]] ''[[Anisodon]] grande'' (formerly ''Chalicotherium grande'')]]
There are many perissodactyl fossils of multivariant form. The major lines of development include the following groups:

*[[File:Paraceratherium-Scale-Diagram-SVG-Steveoc86.svg|thumb|Scale diagram of the [[paraceratheriid]] ''[[Paraceratherium]],'' one of the largest land mammals to have ever existed]]Brontotherioidea were among the earliest known large mammals, consisting of the families of [[Brontotheriidae]] (synonym Titanotheriidae), the most well-known representative being ''[[Megacerops]]'' and the more basal family [[Lambdotheriidae]]. They were generally characterized in their late phase by a bony horn at the transition from the nose to the frontal bone and flat molars suitable for chewing soft plant food. The Brontotheroidea, which were almost exclusively confined to North America and Asia, died out at the beginning of the Upper [[Eocene]].
*[[Equoidea]] also developed in the Eocene. [[Palaeotheriidae]] are known mainly from Europe. In contrast, the horse family ([[Equidae]]) flourished and spread. Over time this group saw a reduction in toe number, extension of the limbs, and the progressive adjustment of the teeth for eating hard grasses.
*[[Chalicotherioidea]] represented another characteristic group, consisting of the families [[Chalicothere|Chalicotheriidae]] and [[Lophiodontidae]]. The Chalicotheriidae developed claws instead of hooves and considerable extension of the forelegs. The best-known genera include ''[[Chalicotherium]]'' and ''[[Moropus]]''. Chalicotherioidea died out in the [[Pleistocene]].
*Rhinocerotoidea (rhino relatives) included a large variety of forms from the Eocene up to the Oligocene, including dog-size leaf feeders, semiaquatic animals, and also huge long-necked animals. Only a few had horns on the nose. The [[Amynodontidae]] were hippo-like, aquatic animals. [[Hyracodontidae]] developed long limbs and long necks that were most pronounced in the ''[[Paraceratherium]]'' (formerly known as ''Baluchitherium'' or ''Indricotherium''), the second largest known land mammal ever to have lived (after ''[[Palaeoloxodon namadicus]]''<ref>{{cite journal | author = Larramendi A | year = 2016 | title = Withers height, body mass and shape of proboscideans | url = http://www.app.pan.pl/article/item/article/item/app001362014.html?pdf=39| journal = Acta Palaeontologica Polonica | volume = 61 | doi = 10.4202/app.00136.2014 | doi-access = free }}</ref>). The rhinos (Rhinocerotidae) emerged in the Middle Eocene; five species survive to the present day.
*[[Tapiroidea]] reached their greatest diversity in the Eocene, when several families lived in Eurasia and North America. They retained a primitive physique and were noted for developing a trunk. The extinct families within this group include the [[Helaletidae]].{{citation needed|date=August 2020}}
*Several mammal groups traditionally classified as [[condylarth]]s, long-understood to be a [[wastebasket taxon]], such as [[Hyopsodontidae|hyopsodontids]] and [[Phenacodontidae|phenacodontids]], are now understood to be part of the odd-toed ungulate assemblage. Phenacodontids seem to be stem-perissodactyls, while hyopsodontids are closely related to horses and brontotheres, despite their more primitive overall appearance.
*[[Desmostylia]]<ref>{{cite journal |author1=Cooper L. N. |author2=Seiffert E. R. |author3=Clementz M. |author4=Madar S. I. |author5=Bajpai S. |author6=Hussain S. T. |author7=Thewissen J. G. M. |display-authors= 3| year = 2014 | title = Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls | journal = PLOS ONE| volume = 9 | issue = 10| page = e109232 | doi = 10.1371/journal.pone.0109232 | pmid = 25295875 | pmc=4189980|bibcode=2014PLoSO...9j9232C |doi-access=free }}</ref> and [[Anthracobunidae]] have traditionally been placed among the [[Afrotheria|afrotheres]], but they may actually represent stem-perissodactyls. They are an early lineage of mammals that took to the water, spreading across semi-aquatic to fully marine niches in the [[Tethys Ocean]] and the northern [[Pacific Ocean|Pacific]]. However, later studies have shown that, while anthracobunids are definite perissodactyls, desmostylians have enough mixed characters to suggest that a position among the Afrotheria is not out of the question.<ref name= "Gheerbrant 2016 e0157556">{{cite journal |last1= Gheerbrant| first1= Emmanuel| last2= Filippo| first2= Andrea | last3= Schmitt|first3= Arnaud | year = 2016 | title = Convergence of Afrotherian and Laurasiatherian Ungulate-Like Mammals: First Morphological Evidence from the Paleocene of Morocco | journal = PLOS ONE| volume = 11 | issue = 7| page = e0157556 | doi = 10.1371/journal.pone.0157556 | pmid=27384169 | pmc=4934866|bibcode=2016PLoSO..1157556G | doi-access= free}}</ref>
* '''Order Perissodactyla'''<ref name="Prothero 2009"/>
**'''Superfamily Brontotherioidea'''
*** †[[Brontotheriidae]]
**'''Suborder Hippomorpha'''
*** †[[Hyopsodontidae]]<ref>{{cite journal |last1= Ravel| first1= Anthony | last2= Orliac| first2= Maeva | year = 2014 | title = The inner ear morphology of the 'condylarthran' Hyopsodus lepidus | journal = Historical Biology | volume = 27 | issue = 8| page = 8 | doi = 10.1080/08912963.2014.915823 |s2cid=84391276 }}</ref>
*** †[[Pachynolophidae]]<ref name="Badiola2003">{{cite journal |last1= Badiola |first1= A. |last2= Pareda-Suberbiola |first2= X. |last3= Cuesta |first3= M. |date= 2003 |title= A new species of ''Pachynolophus'' (Mammalia, Perissodactyla) from Zambrana (Álava, Basque-Cantabrian Region). Phylogenetic analysis of ''Pachynolophus'' and first mention in the Late Eocene of the Iberian Peninsula |journal= Geobios |volume= 38 |issue= 1 |pages= 1–16 |doi= 10.1016/j.geobios.2003.07.005}}</ref>
*** '''Superfamily Equoidea'''
**** †[[Indolophidae]]<ref name="Tsubamoto2003">{{cite journal |last1= Tsubamoto |first1= T. |last2= Tun |first2= S.T. |display-authors = etal |date= 2003 |title= Reevaluation of some ungulate mammals from the Eocene Pondaung Formation, Myanmar |journal= Paleontological Research |volume= 7 |issue= 3 |pages= 219–43 |doi= 10.2517/prpsj.7.219|s2cid= 84061253 |doi-access= free |bibcode= 2003PalRe...7..219T }}</ref>
**** †[[Palaeotheriidae]] (might be a basal perissodactyl grade instead)
** '''Clade Tapiromorpha'''
*** †[[Isectolophidae]]<ref name="Holbrook 2001"/> (a basal family of Tapiromorpha; from the Eocene epoch)
*** †'''Suborder [[Ancylopoda]]'''
**** †[[Lophiodontidae]]
**** '''Superfamily [[Chalicotherioidea]]'''
***** †[[Eomoropidae]] (basal grade of chalicotheroids)
***** †[[Chalicothere|Chalicotheriidae]]
*** '''Suborder Ceratomorpha'''
**** '''Superfamily [[Rhinocerotoidea]]'''
***** †[[Amynodontidae]]
***** †[[Hyracodontidae]]
**** '''Superfamily [[Tapiroidea]]'''
***** †[[Deperetellidae]]
***** †[[Rhodopagidae]] (sometimes recognized as a subfamily of deperetellids)
***** †[[Lophialetidae]]<ref name=Gong2019>{{cite journal |last1= Gong |first1= Y. |last2= Wang |first2= Y. |display-authors = etal |date= December 2019 |title= Dietary adaptations and palaeoecology of Lophialetidae (Mammalia, Tapiroidea) from the Eocene of the Erlian Basin, China: combined evidence from mesowear and stable isotope analyses |journal= Palaeontology |volume= 63 |issue= 4 |pages= 547–564 |doi= 10.1111/pala.12471|s2cid= 214053761 }}</ref>
***** †[[Eoletidae]] (sometimes recognized as a subfamily of lophialetids)
** †[[Anthracobunidae]]<ref name="Cooper2014">{{Cite journal | doi = 10.1371/journal.pone.0109232| pmid = 25295875| title = Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls| journal = PLOS ONE| volume = 9| issue = 10| pages = e109232| date = 2014-10-08| last1 = Cooper | first1 = L. N. | last2 = Seiffert | first2 = E. R. | last3 = Clementz | first3 = M. | last4 = Madar | first4 = S. I. | last5 = Bajpai | first5 = S. | last6 = Hussain | first6 = S. T. | last7 = Thewissen | first7 = J. G. M.| pmc=4189980| bibcode = 2014PLoSO...9j9232C| doi-access = free}}</ref> (a family of stem-perissodactyls; from the Early to Middle Eocene epoch)
** †[[Phenacodontidae]]<ref name="Cooper2014"/> (a clade of stem-perissodactyls; from the Early Palaeocene to the Middle Eocene epoch)