Editing Ungulate (section)

==Evolutionary history==
[[File:Protungulatum.png|thumb|left|Speculative [[Paleoart|reconstruction]] of the controversial ''Protungulatum'']]
[[File:Cladogram of Cetacea within Artiodactyla.png|thumb|upright=1.7|[[Cladogram]] showing relationships within Euungulata<ref name=Spauldingetal2009/>]]

[[Perissodactyla]] and [[Artiodactyla]]  include the majority of large land mammals. These two groups first appeared during the late [[Paleocene]], rapidly spreading to a wide variety of species on numerous continents, and have developed in parallel since that time. Some scientists believed that modern ungulates were descended from an [[evolutionary grade]] of mammals known as the [[condylarth]]s.<ref name=RoseArchaicUng>{{cite book|last=Rose|first=Kenneth D.|title=The beginning of the Age of Mammals|year=2006|publisher=Johns Hopkins University Press|location=Baltimore|isbn=9780801892219|chapter=Archaic Ungulates}}</ref> The earliest known member of this group may have been the tiny ''[[Protungulatum]]'', a mammal that co-existed with the last of non-avian [[dinosaur]]s 66&nbsp;million years ago.<ref>Jehle, Martin [http://www.paleocene-mammals.de/condylarths.htm#Arctocyonidae "Condylarths: Archaic hoofed mammals"] in ''Paleocene mammals of the world''</ref> However, many authorities do not consider it a true placental, let alone an ungulate.<ref>{{cite journal | last1 = Archibald | first1 = J. David | last2 = Zhang | first2 = Yue | last3 = Harper | first3 = Tony | last4 = Cifelli | first4 = Richard L. | year = 2011 | title = Protungulatum, Confirmed Cretaceous Occurrence of an Otherwise Paleocene Eutherian (Placental?) Mammal | journal = Journal of Mammalian Evolution | volume = 18| issue = 3| pages = 153–161| doi = 10.1007/s10914-011-9162-1 | s2cid = 16724836 }}</ref> The enigmatic [[dinocerata]]ns were among the first large herbivorous mammals, although their exact relationship with other mammals is still debated with one of the theories being that they might just be distant relatives to living ungulates; the most recent study recovers them as within the true ungulate assemblage, closest to ''[[Carodnia]]''.<ref name="Berger-Benjamin">{{cite conference |last=Burger |first=Benjamin J. |date=15 October 2015 |title=The Systematic Position of the Saber-Toothed and Horned Giants of the Eocene: The Uintatheres (Order Dinocerata) |url=http://www.benjamin-burger.org/wp-content/uploads/2019/12/SVP-Poster-Ben-Burger-2015.pdf |location=Dallas |conference=Society of Vertebrate Paleontology 75th Annual Meeting |access-date=20 February 2020 }} [http://vertpaleo.org/PDFS/SVP-2015-Program-and-Abstract-Book-9-22-2015.aspx Conference abstract (p. 99)] {{Webarchive|url=https://web.archive.org/web/20191224042705/http://vertpaleo.org/PDFS/SVP-2015-Program-and-Abstract-Book-9-22-2015.aspx |date=2019-12-24 }}. Explanation and conclusions: {{YouTube|B6lmLo14Cc0|Episode 17: Systematic position of the Uintatheres (Order Dinocerata)}}.</ref>

In Australia, the recently-extinct [[marsupial]] ''[[Chaeropus]]'' ("pig-footed bandicoot") also developed hooves similar to those of artiodactyls,<ref>{{cite journal|last1=Sánchez-Villagra|first1=Marcelo R|year=2013|title=Why were There Fewer Marsupials than Placentals? On the Relevance of Geography and Physiology to Evolutionary Patterns of Mammalian Diversity and Disparity|url=https://www.zora.uzh.ch/id/eprint/71489/10/ZORA_NL_71489.pdf|journal=Journal of Mammalian Evolution|volume=20|issue=4|pages=279–290|doi=10.1007/s10914-012-9220-3|s2cid=18789008}}</ref> an example of [[convergent evolution]].

===Perissodactyl evolution ===
{{See also|Evolution of the horse}}
[[File:Eurohippus parvulus.jpg|thumb|left|Restoration of ''[[Eurohippus parvulus]]'', a mid- to late Eocene equid of Europe ([[Natural History Museum, Berlin]])]]
[[File:Sa-rhino-skin.jpg|thumb|The thick dermal [[Armour (anatomy)|armour]] of the Rhinoceros evolved at the same time as shearing [[tusks]].<ref>{{cite thesis |last=Hieronymus|first=Tobin L.|title=Osteological Correlates of Cephalic Skin Structures in Amniota: Documenting the Evolution of Display and Feeding Structures with Fossil Data |type=PhD dissertation |publisher=Ohio University |url=http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1237491191 |access-date=2022-11-12 |page=3|date=March 2009}}</ref>]]

Perissodactyls were thought to have evolved from the [[Phenacodontidae]], small, sheep-sized animals that were already showing signs of anatomical features that their descendants would inherit (the reduction of digit I and V for example).<ref name="Jehle-Condylarths"/> By the start of the [[Eocene]], 55&nbsp;million years ago (Mya), they had diversified and spread out to occupy several continents. [[Horse]]s and [[tapir]]s both evolved in North America;<ref name=MamEv>{{cite book|author= Savage, RJG, & Long, MR|year= 1986|title= Mammal Evolution: an illustrated guide|publisher= Facts on File|location= New York|isbn= 978-0-8160-1194-0|oclc= 12949777|url-access= registration|url= https://archive.org/details/mammalevolutioni0000sava}}</ref> rhinoceroses appear to have developed in [[Asia]] from tapir-like animals and then colonised the Americas during the middle Eocene (about 45&nbsp;Mya). Of the approximately 15 families, only three survive (McKenna and Bell, 1997; Hooker, 2005). These families were very diverse in form and size; they included the enormous [[Brontotheriidae|brontotheres]] and the bizarre [[Chalicotheriidae|chalicothere]]s. The largest perissodactyl, an Asian rhinoceros called ''[[Paraceratherium]]'', reached {{convert|15|tonne}}, more than twice the weight of an [[elephant]].<ref name=Benton>{{cite book|author= Benton, Michael J. |year= 1997 |title= Vertebrate Palaeontology |publisher= Chapman & Hall |location= London |page= 343 |isbn= 0-412-73810-4}}</ref>

It has been found in a cladistic study that the [[Anthracobunidae|anthracobunid]]s and the [[desmostylia]]ns – two lineages that have been previously classified as [[Afrotheria]]ns (more specifically closer to elephants) – have been classified as a clade that is closely related to the perissodactyls.<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.
|author5-link=Sunil Bajpai
|author7-link=Hans Thewissen
  | pmc=4189980
| bibcode = 2014PLoSO...9j9232C
 | doi-access = free
 }}</ref> The desmostylians were large amphibious quadrupeds with massive limbs and a short tail.<ref name="Gheerbrant-etal-2005">{{Harvnb|Gheerbrant|Domning|Tassy|2005|pp=95–6}}</ref>{{Missing long citation|date=July 2023}} They grew to {{Convert|1.8|m|ft|sigfig=1}} in length and were thought to have weighed more than {{convert|200|kg|lb}}. Their [[fossil]]s were known from the northern [[Pacific Rim]],<ref>{{Cite journal
  | last       = Gingerich
  | first      = Philip D.
  | author-link = Philip D. Gingerich
  | title      = Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian ''Desmostylus''
  | year       = 2005
  | journal    = Journal of Mammalian Evolution
  | volume     = 12
  | issue      = 1/2
  | url        = http://deepblue.lib.umich.edu/bitstream/handle/2027.42/44971/10914_2005_Article_5719.pdf
  | doi        = 10.1007/s10914-005-5719-1
  | pages      = 183–194
| hdl = 2027.42/44971
 | s2cid = 7812089
 | hdl-access= free
  }}</ref> from southern [[Japan]] through [[Russia]], the [[Aleutian Islands]] and the Pacific coast of [[North America]] to the southern tip of [[Baja California]]. Their dental and skeletal form suggests desmostylians were aquatic [[herbivore]]s dependent on [[littoral]] habitats. Their name refers to their highly distinctive molars, in which each cusp was modified into hollow columns, so that a typical molar would have resembled a cluster of pipes, or in the case of worn molars, volcanoes. They were the only marine mammals to have gone extinct.

The South American [[South American native ungulates|meridiungulate]]s contain the somewhat tapir-like [[Pyrotheria|pyrotheres]] and [[Astrapotheria|astrapotheres]], the mesaxonic [[Litopterna|litoptern]]s and the diverse [[Notoungulata|notoungulates]]. As a whole, meridiungulates were said to have evolved from animals like ''[[Hyopsodus]]''.<ref name="Jehle-Condylarths"/> For a while their relationships with other ungulates were a mystery. Some [[paleontologists]] have even challenged the [[monophyly]] of Meridiungulata by suggesting that the pyrotheres may be more closely related to other mammals, such as [[Embrithopoda]] (an African order that were related to [[elephant]]s) than to other South American ungulates.<ref name=Shockey>{{cite journal |author1=Shockey, B.J. |author2=Anaya, F.  |name-list-style=amp | year = 2004 | title = ''Pyrotherium macfaddeni'', sp. nov. (late Oligocene, Bolivia) and the pedal morphology of pyrotheres | journal = Journal of Vertebrate Paleontology | volume = 24 | issue = 2 | pages = 481–488 | doi = 10.1671/2521|bibcode=2004JVPal..24..481S |s2cid=83680724 }}</ref> A recent study based on bone collagen has found that at least litopterns and the notoungulates were closely related to the perissodactyls.<ref name="Welker2015">{{cite journal |title=Ancient proteins resolve the evolutionary history of Darwin's South American ungulates |doi=10.1038/nature14249 |date=18 March 2015 |volume=522 |issue=7554 |journal=Nature |pages=81–84 |pmid=25799987 |last1=Welker |first1=F |last2=Collins |first2=MJ |last3=Thomas |first3=JA |last4=Wadsley |first4=M |last5=Brace |first5=S |last6=Cappellini |first6=E |last7=Turvey |first7=ST |last8=Reguero |first8=M |last9=Gelfo |first9=JN |last10=Kramarz |first10=A |last11=Burger |first11=J |last12=Thomas-Oates |first12=J |last13=Ashford |first13=DA |last14=Ashton |first14=PD |last15=Rowsell |first15=K |last16=Porter |first16=DM |last17=Kessler |first17=B |last18=Fischer |first18=R |last19=Baessmann |first19=C |last20=Kaspar |first20=S |last21=Olsen |first21=JV |last22=Kiley |first22=P |last23=Elliott |first23=JA |last24=Kelstrup |first24=CD |last25=Mullin |first25=V |last26=Hofreiter |first26=M |last27=Willerslev |first27=E |last28=Hublin |first28=JJ |last29=Orlando |first29=L |last30=Barnes |first30=I |last31=MacPhee |first31=RD |author2-link=Matthew Collins (academic)|author12-link=Jane Thomas-Oates|author17-link=Benedikt Kessler|author27-link=Eske Willerslev|bibcode=2015Natur.522...81W |hdl=11336/14769 |s2cid=4467386 |url=http://eprints.whiterose.ac.uk/91438/1/Welker_postprint.docx|hdl-access=free }}</ref>

The oldest known [[fossil]]s assigned to [[Equidae]] date from the early [[Eocene]], 54&nbsp;million years ago. They had been assigned to the genus ''[[Hyracotherium]]'', but the [[type species]] of that genus is now considered not a member of this family, but the other species have been split off into different genera.  These early Equidae 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 were 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= 978-1-84028-152-1}}</ref> Later species reduced the number of toes, and developed teeth more suited for grinding up grass and other tough plant food.

Rhinocerotoids diverged from other [[perissodactyls]] by the early Eocene. Fossils of ''[[Hyrachyus|Hyrachyus eximus]]'' found in North America date to this period. This small hornless ancestor resembled a tapir or small horse more than a rhino. Three families, sometimes grouped together as the [[Taxonomic rank|superfamily]] Rhinocerotoidea, evolved in the late Eocene: [[Hyracodontidae]], [[Amynodontidae]] and [[Rhinoceros|Rhinocerotidae]], thus creating an explosion of diversity unmatched for a while until environmental changes drastically eliminated several species.

The first tapirids, such as ''[[Heptodon]]'', appeared in the early Eocene.<ref>Ballenger, L. and Myers, P. (2001). [http://animaldiversity.ummz.umich.edu/site/accounts/information/Tapiridae.html "Family Tapiridae"], ''Animal Diversity Web''. Retrieved November 22, 2007.</ref> They appeared very similar to modern forms, but were about half the size, and lacked the proboscis. The first true tapirs appeared in the [[Oligocene]]. By the [[Miocene]], such genera as ''[[Miotapirus]]'' were almost indistinguishable from the extant species. Asian and American tapirs were believed to have diverged around 20 to 30&nbsp;million years ago; and tapirs migrated from North America to South America around 3&nbsp;million years ago, as part of the [[Great American Interchange]].<ref>{{Cite journal | doi = 10.1007/BF02077448 | last1 = Ashley | first1 = M.V. | last2 = Norman | first2 = J.E. | last3 = Stross | first3 = L. | year = 1996 | title = Phylogenetic analysis of the perissodactyl family tapiridae using mitochondrial cytochrome c oxidase (COII) sequences | journal =   Journal of Mammalian Evolution| volume = 3 | issue = 4| pages = 315–326 | s2cid = 24948320 }}</ref>

Perissodactyls were the dominant group of large terrestrial browsers right through the Oligocene. However, the rise of grasses in the Miocene (about 20&nbsp;Mya) saw a major change: the artiodactyl species with their more complex stomachs were better able to adapt to a coarse, low-nutrition diet, and soon rose to prominence. Nevertheless, many perissodactyl species survived and prospered until the late [[Pleistocene]] (about 10,000 years ago) when they faced the pressure of human hunting and habitat change.

===Artiodactyl evolution===
[[File:Arctocyon DB.jpg|thumb|''[[Arctocyon]]'', an [[Arctocyonidae|arctocyonid]]]]
The artiodactyls were thought to have evolved from a small group of condylarths, [[Arctocyonidae]], which were unspecialized, superficially raccoon-like to bear-like omnivores from the Early [[Paleocene]] (about 65 to 60&nbsp;million years ago). They had relatively short limbs lacking specializations associated with their relatives (e.g. reduced side digits, fused bones, and hooves),<ref name="Jehle-Condylarths">Jehle, Martin [http://www.paleocene-mammals.de/condylarths.htm#Phenacodontidae "Condylarths: Archaic hoofed mammals"] in ''Paleocene mammals of the world''</ref> and long, heavy tails. Their primitive anatomy makes it unlikely that they were able to run down prey, but with their powerful proportions, claws, and long canines, they may have been able to overpower smaller animals in surprise attacks.<ref name="Jehle-Condylarths"/> Evidently these mammals soon evolved into two separate lineages: the [[mesonychia]]ns and the artiodactyls.

[[File:Anoplotherium commune.jpg|thumb|left|Skeleton of ''[[Anoplotherium commune]]'', an early artiodactyl with unusual features such as a long tail]]
The first artiodactyls looked like today's [[chevrotain]]s or pigs: small, short-legged creatures that ate [[leaves]] and the soft parts of [[plants]]. By the Late Eocene (46&nbsp;million years ago), the three modern suborders had already developed: [[Suina]] (the [[pig]] group); [[Tylopoda]] (the [[camel]] group); and [[Ruminantia]] (the [[goat]] and [[cattle]] group). Nevertheless, artiodactyls were far from dominant at that time: the perissodactyls were much more successful and far more numerous. Artiodactyls survived in niche roles, usually occupying marginal [[habitat (ecology)|habitats]], and it is presumably at that time that they developed their complex [[digestive system]]s, which allowed them to survive on lower-grade food. While most artiodactyls were taking over the niches left behind by several extinct perissodactyls, one lineage of artiodactyls began to venture out into the seas.

====Cetacean evolution====
{{See also|Evolution of cetaceans}}
[[File:Ambulocetus natans.jpg|thumb|Skeleton of ''[[Ambulocetus natans]]'', a stem whale]]
The traditional theory of cetacean evolution was that cetaceans were related to the [[Mesonychia|mesonychian]]. These animals had unusual triangular teeth very similar to those of primitive cetaceans.  This is why scientists long believed that cetaceans evolved from a form of mesonychian. Today, many scientists believe cetaceans evolved from the same stock that gave rise to hippopotamuses. This hypothesized ancestral group likely split into two branches around {{mya|54|million years ago}}.<ref name="Genomes" /> One branch would [[Evolution of cetaceans|evolve into cetaceans]], possibly beginning about {{mya|52|million years ago}} with the proto-whale ''[[Pakicetus]]'' and other early cetacean ancestors collectively known as [[Archaeoceti]], which eventually underwent [[aquatic adaptation]] into the completely aquatic [[cetacea]]ns.<ref name="Cetartiodactyla">{{cite journal |last=Boisserie |first=Jean-Renaud |author2=Lihoreau, F. |author3=Brunet, M. |date=February 2005 |title= The position of Hippopotamidae within Cetartiodactyla |journal= [[Proceedings of the National Academy of Sciences]] |volume= 102 |issue= 5 |pages= 1537–1541|doi= 10.1073/pnas.0409518102 |pmc=547867|bibcode = 2005PNAS..102.1537B |pmid= 15677331 |doi-access=free }}</ref> The other branch became the [[anthracotheriidae|anthracotheres]], a large family of four-legged beasts, the earliest of whom in the late [[Eocene]] would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into [[Hippopotamidae]], became extinct during the [[Pliocene]] without leaving any descendants.<ref name="ScienceNews">{{Cite web | title = Scientists find missing link between the dolphin, whale and its closest relative, the hippo | date = 2005-01-25 | access-date = 2007-06-18 | url = http://www.sciencenewsdaily.org/story-2806.html | work = Science News Daily | url-status = dead | archive-url = https://web.archive.org/web/20070304214747/http://www.sciencenewsdaily.org/story-2806.html | archive-date = 2007-03-04 }}</ref>

The family [[Raoellidae]] is said to be the closest artiodactyl family to the cetaceans.<ref>{{cite journal |last1=Thewissen |first1=J. G. M. |year=2007 |title=Whales originated from aquatic artiodactyls in the Eocene epoch of India |journal=Nature |volume=450 |issue=7173 |pages=1190–1194 |doi=10.1038/nature06343 |url= http://repository.ias.ac.in/4642/1/316.pdf|pmid=18097400 |last2=Cooper |first2=LN |last3=Clementz |first3=MT |last4=Bajpai |first4=S|author4-link=Sunil Bajpai |last5=Tiwari |first5=BN |bibcode=2007Natur.450.1190T|s2cid=4416444 }}</ref><ref>{{cite magazine
|url=http://www.sciam.com/article.cfm?id=closest-whale-cousin
|title=Closest Whale Cousin—A Fox-Size Deer? Researchers split on closest evolutionary kin to whales and dolphins
|first=JR
|last=Minkel 
|magazine=Scientific American
|date=2007-12-19}}</ref> Consequentially, new theories in cetacean evolution hypothesize that whales and their ancestors escaped predation, not competition, by slowly adapting to the ocean.<ref name=GuardianIndohyus>{{cite news |url=https://www.theguardian.com/science/2007/dec/19/whale.deer?gusrc=rss&feed=networkfront |title=Whales may be descended from a small deer-like animal  |access-date=2007-12-21 |author= Sample, Ian|date=December 19, 2007|work=[[Guardian Unlimited]] |location=London}}</ref><ref name=TheLoom>{{cite web |url=http://scienceblogs.com/loom/2007/12/19/whales_from_so_humble_a_beginn.php |title=The Loom : Whales: From So Humble A Beginning... |access-date=2007-12-21 |author=Zimmer, Carl |author-link=Carl Zimmer |date=December 19, 2007 |publisher=[[ScienceBlogs]] |archive-date=2007-12-21 |archive-url=https://web.archive.org/web/20071221103928/http://scienceblogs.com/loom/2007/12/19/whales_from_so_humble_a_beginn.php |url-status=dead }}</ref><ref name=PharyngulaIndohyus>{{cite web |url=http://scienceblogs.com/pharyngula/2007/12/indohyus.php |title=Pharyngula: Indohyus |access-date=2007-12-21 |author=Myers, P.Z. |author-link=PZ Myers |date=December 19, 2007 |work=[[Pharyngula (blog)|Pharyngula]] |publisher=[[ScienceBlogs]] |archive-date=2007-12-20 |archive-url=https://web.archive.org/web/20071220115757/http://scienceblogs.com/pharyngula/2007/12/indohyus.php |url-status=dead }}</ref>

===Mesonychian evolution===
[[File:Mesonyx.jpg|thumb|left|Restoration of ''Mesonyx'']]
Mesonychians were depicted as "wolves on hooves" and were the first major mammalian predators, appearing in the Paleocene.<ref name="Jehle">Jehle, Martin [http://www.paleocene-mammals.de/predators.htm#Carnivorous "Carnivores, creodonts and carnivorous ungulates: Mammals become predators"] in ''Paleocene mammals of the world''</ref>  Early mesonychians had five digits on their feet, which probably rested flat on the ground during walking ([[plantigrade]] locomotion), but later mesonychians had four digits that ended in tiny hooves on all of their toes and were increasingly well adapted to running. Like running members of the even-toed ungulates, mesonychians (''Pachyaena'', for example) walked on their digits ([[digitigrade]] locomotion).<ref name="Jehle"/> Mesonychians fared very poorly at the close of the Eocene epoch, with only one genus, ''[[Mongolestes]]'',<ref name=Jin05>{{cite journal|author=Jin, X. |year=2005 |title=Mesonychids from Lushi Basin, Henan Province, China ''(in Chinese with English summary)'' |journal=Vertebrata PalAsiatica |volume=43 |issue=2 |pages=151–164 |url=http://www.ivpp.ac.cn/pdf/magazine308.pdf }}{{dead link|date=June 2016|bot=medic}}{{cbignore|bot=medic}}</ref> surviving into the Early [[Oligocene]] epoch, as the climate changed and fierce competition arose from the better adapted [[creodont]]s.