Editing Moropus

{{Short description|Extinct genus of mammals}}
{{Automatic taxobox
| fossil_range = [[Early Miocene|Early]]-[[Middle Miocene]], {{fossil range|20.43|13.6|ref=<ref name = "Fossilworks">{{cite web
 | title = ''Moropus'' in the Paleobiology Database | work = [[Fossilworks]]
 | url = https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=43084
 | access-date = 17 December 2021}}</ref>}}
| image = Moropus elatus.jpg
| image_caption = ''Moropus elatus'' skeleton at the<br />[[National Museum of Natural History]],<br />[[Washington, DC]]
| image2 = Moropus Head .jpg
| image2_caption = Reconstruction of the head of ''M. elatus''
| taxon = Moropus
| authority = [[Othniel Charles Marsh|Marsh]], 1877
| type_species = '''''Moropus distans'''''
| type_species_authority = Marsh, 1877
| subdivision_ranks = Species
| subdivision = *''M. distans'' <small>Marsh, 1877</small>
*''M. elatus'' <small>Marsh, 1877</small>
*''M. hollandi'' <small>[[O. A. Peterson|Peterson]], 1907</small>
*''M. matthewi'' <small>[[William Jacob Holland|Holland]] & Peterson, 1913</small>
*''M. merriami'' <small>Peterson, 1913</small>
*''M. oregonensis'' <small>[[Joseph Leidy|Leidy]], 1873</small>
*''M. senex'' <small>Marsh, 1877</small>
| synonyms = {{collapsible list|bullets = true|title=<small>Synonyms of ''M. elatus''</small>
| ''M. cooki'' <small>[[Erwin Hinckley Barbour|Barbour]], 1908</small>
| ''M. petersoni'' <small>Holland, 1908</small>
| ''M. parvus'' <small>Barbour, 1909</small>
}}
}}

'''''Moropus''''' (meaning "slow foot")<ref>{{Citation |last=Carlton |first=Robert L. |title=M |date=2018 |work=A Concise Dictionary of Paleontology |pages=165–184 |editor-last=Carlton |editor-first=Robert L. |url=https://link.springer.com/chapter/10.1007/978-3-319-73055-4_13 |access-date=2025-01-11 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-73055-4_13 |isbn=978-3-319-73055-4|url-access=subscription }}</ref> is an extinct genus of large [[perissodactyl]] [[mammal]] in the [[chalicothere]] family. They were endemic to [[North America]] during the [[Miocene]] from ~20.4–13.6 [[Mya (unit)|Mya]], existing for approximately {{Mya|20.4-13.6|million years}}. ''Moropus'' belonged to the [[Schizotheriinae|schizotheriine]] subfamily of chalicotheres, and has the best fossil record of any member of this group; numbers of individuals, including complete skeletons, have been found. The type species of ''Moropus'', ''M. distans'', was named by [[Othniel Charles Marsh]] in 1877, alongside two other species, ''M. elatus'' and ''M. senex''. Three more species have been named since. Others have been named, but have either been invalidated for one reason or another, or reclassified to other genera.

Among the largest chalicotheres, some specimens of ''Moropus'' stood {{convert|8|ft|m|abbr=on|order=flip}} at the shoulder. One specimen had an estimated body mass of {{Convert|1179|kg|lb|abbr=on}}. Its dental anatomy was similar to [[Ruminant|ruminants]], suggesting a similar method of cropping vegetation. Retracted nasal bones suggest a long upper lip, and a wide gap between the lower incisors and cheek teeth, called a [[diastema]], would provide room for a long tongue to extend from the mouth at an angle. Together, the upper lip and tongue may have been used to pull down vegetation. Though not as adept at bipedalism as the related ''[[Chalicotherium]]'', it may nonetheless have reared up on two legs to [[Browsing (herbivory)|browse]] on vegetation, using its claws to hook into the bark of a tree or using them to pull down leaves that would otherwise have been unreachable. ''Moropus'' may have been sexually dimorphic, with the males being larger than the females. 

== Taxonomy ==

=== Early history ===
The first of the remains currently assigned to ''Moropus'' was a partial right [[maxilla]] (YPM 10030), uncovered at some point prior to 1873. In that year, the specimen was described YPM 10030, initially mistakenly attributed ''to Lophiodon''.<ref>{{Cite book |last=Leidy |first=Joseph |url=https://www.biodiversitylibrary.org/bibliography/61805 |title=Contributions to the extinct vertebrate fauna of the western territories |date=1873 |publisher=Govt. Print. Off |location=Washington}}</ref> After its discovery, multiple more complete specimens were discovered in the [[Miocene]] strata of the [[John Day Fossil Beds National Monument|John Day Fossil Beds]] of Oregon.<ref name=":0">{{Cite journal |last1=Holland |first1=William Jacob |author-link1=William Jacob Holland |last2=Peterson |first2=Olof August |date=1913 |title=The osteology of the Chalicotheroidea with special reference to a mounted skeleton of Moropus elatus Marsh, now installed in the Carnegie museum |url=https://www.biodiversitylibrary.org/part/211102 |journal=Memoirs of the Carnegie Museum |volume=3 |issue=2 |pages=189––406 |doi=10.5962/p.211102|doi-access=free }}</ref> In 1877, [[Othniel Charles Marsh]] formally described the specimens, assigning to them the genus name ''Moropus''. The type species of ''Moropus'', ''M. distans'', was based only on fragments of the hind foot.<ref name=":0" /><ref name=":1">{{Cite journal |last=Marsh |first=Othniel Charles |author-link=Othniel Charles Marsh |date=1877 |title=Notice of Some New Vertebrate Fossils |url=https://marsh.dinodb.com/marsh/Marsh%201877%20-%20Notice%20of%20some%20new%20vertebrate%20fossils.pdf |journal=American Journal of Science |volume=81 |issue=81 |pages=249–256|doi=10.2475/ajs.s3-14.81.249 |bibcode=1877AmJS...14..249M }}</ref> Two other species, ''M. elatus'' and ''M. senex'', were also described. At first, Marsh believed that ''Moropus'' belonged to the order [[Xenarthra|Edentata]], which historically included any mammal that lacked [[incisor]] teeth. Though he noted affinities with the African ''[[Ancylotherium]]'', he opted to erect a new [[Family (biology)|family]], Moropodidae, to exclusively include ''Moropus''.<ref name=":1" /> In 1908, geologist and palaeontologist [[Erwin Hinckley Barbour]] noted that ''Moropus'' had occasionally been treated as a form intermediate between edendates and [[Ungulate|ungulates]], though affirmed that it was definitely a true ungulate.<ref name=":2">{{Cite journal |last=Barbour |first=Erwin |date=1908-01-01 |title=The Skull of Moropus |url=https://digitalcommons.unl.edu/conservationsurvey/864/ |journal=Conservation and Survey Division}}</ref>

In 1913, Olof August Peterson named a new species of ''Moropus'', ''M. hollandi'', from limb elements recovered in 1901, at first mistakenly assigned to ''M. elatus''.<ref>{{Cite journal |last=Peterson |first=O. A. |date=1913-11-07 |title=A New Species of Moropus ( M. hollandi ) from the Base of the Middle Miocene of Western Nebraska |url=https://www.science.org/doi/10.1126/science.38.984.673.a |journal=Science |language=en |volume=38 |issue=984 |pages=673–680 |doi=10.1126/science.38.984.673.a |pmid=17732680 |issn=0036-8075|url-access=subscription }}</ref> In a 1913 [[monograph]] on chalicothere taxonomy, ''Moropus'' in particular, Peterson and [[William Jacob Holland]] recognised two additional species, ''M. matthewi'' and ''M. merriami'', and reassigned ''Moropus'' to [[Chalicotheriidae]].<ref name=":0" />

=== Invalid or reassigned species ===
In 1892, Barbour came into possession of a partial mammal skeleton from the [[Agate Fossil Beds National Monument]].<ref>{{Cite journal |last=Cockerell |first=T. D. A. |date=1923 |title=Fossil Mammals at the Colorado Museum of Natural History |url=https://www.jstor.org/stable/3693057 |journal=The Scientific Monthly |volume=17 |issue=3 |pages=271–277 |jstor=3693057 |issn=0096-3771}}</ref> He assigned the specimen to ''Moropus'', and named a new species, ''M. cooki'' (after Harold Cook, who discovered it) based on it. However, Peterson and Holland considered ''M. cooki'' a junior synonym of ''M. elatus''.<ref name=":0" /> In 1907, Holland named ''M. petersoni'', also from the Agate Fossil Beds, after Peterson.<ref>{{Cite journal |last=Holland |first=W. J. |date=1908 |title=A New Species of the Genus Moropus |url=https://www.jstor.org/stable/1634948 |journal=Science |volume=28 |issue=727 |pages=809–810 |doi=10.1126/science.28.727.809 |jstor=1634948 |pmid=17780444 |bibcode=1908Sci....28..809H |issn=0036-8075}}</ref> Later, in 1975, Margery Chalifoux Coombs suggested that ''M. petersoni'' was instead the same taxon as ''M. elatus'', and that its differences could be explained through [[sexual dimorphism]] {{See below|[[#Sexual dimorphism|below]]}}.<ref name=":3">{{Cite journal |last=Coombs |first=Margery Chalifoux |date=1975 |title=Sexual Dimorphism in Chalicotheres (Mammalia, Perissodactyla) |url=https://www.jstor.org/stable/2412697 |journal=Systematic Zoology |volume=24 |issue=1 |pages=55–62 |doi=10.2307/2412697 |jstor=2412697 |issn=0039-7989|url-access=subscription }}</ref> In 1935, Soviet palaeontologist K.K. Flerov named an Asian species of ''Moropus'', "M." ''betpakdalensis'' from Kazakhstan.<ref>{{Cite journal |last=Flerov |first=K. K. |date=1938 |title=Remains of Ungulata from Betpak–dala |journal=C. R. Acad. Sci. |volume=21 |pages=94–96}}</ref> This taxon has since been reassigned to a genus of its own, ''[[Borissiakia]]''.<ref name="butler1965">{{Cite journal |last=Butler |first=Percy Milton |author-link=Percy M. Butler |date=1965 |title=Fossil mammals of Africa No. 18: East African Miocene and Pleistocene chalicotheres |url=https://www.biodiversitylibrary.org/part/83495 |journal=Bulletin of the British Museum (Natural History) Geology |volume=10 |pages=163–237}}</ref> Another purported Asian ''Moropus'', "M''.''" ''huangheensis'', has also been reassigned to ''Borissiakia''.<ref>{{Cite journal |last1=Li |first1=Zhaoyu |last2=Mörs |first2=Thomas |last3=Zhang |first3=Yunxiang |last4=Xie |first4=Kun |last5=Li |first5=Yongxiang |date=2022-12-01 |title=New Material of Schizotheriine Chalicothere (Perissodactyla, Chalicotheriidae) from the Xianshuihe Formation (Early Miocene) of Lanzhou Basin, Northwest China |url=https://link.springer.com/article/10.1007/s10914-022-09619-3 |journal=Journal of Mammalian Evolution |language=en |volume=29 |issue=4 |pages=877–889 |doi=10.1007/s10914-022-09619-3 |issn=1573-7055}}</ref>

=== Taxonomy ===
Chalicotheres are part of the order [[Perissodactyla]], which includes modern [[Equidae|equines]], [[Rhinoceros|rhinoceroses]], and [[Tapir|tapirs]], as well as extinct groups like [[Brontotheriidae|brontotheres]].<ref name="MamEv2">{{cite book |author1=Savage, RJG |url=https://archive.org/details/mammalevolutioni0000sava |title=Mammal Evolution: an illustrated guide |author2=Long, MR |publisher=Facts on File |year=1986 |isbn=0-8160-1194-X |location=New York |pages=[https://archive.org/details/mammalevolutioni0000sava/page/198 198–199] |url-access=registration}}</ref><ref name=":4">{{Cite journal |last1=Holbrook |first1=Luke T. |last2=Lucas |first2=Spencer G. |last3=Emry |first3=Robert J. |date=2004 |title=Skulls of the Eocene Perissodactyls (Mammalia) "Homogalax" and "Isectolophus" |url=https://www.jstor.org/stable/4524789 |journal=Journal of Vertebrate Paleontology |volume=24 |issue=4 |pages=951–956 |doi=10.1671/0272-4634(2004)024[0951:SOTEPM]2.0.CO;2 |issn=0272-4634 |jstor=4524789 |s2cid=86289060|url-access=subscription }}</ref> As the early evolution of perissodactyls is still unresolved, their closest relatives among other perissodactyl groups is obscure.<ref name=":4" /> They are generally placed as part of the clade [[Ancylopoda]] alongside their close relatives [[Lophiodontidae]]. Many studies considered them as closer to [[Perissodactyla|Ceratomorpha]] (which includes tapirs and rhinoceroses) than [[Equoidea]].<ref>{{Cite journal |last=Froehlich |first=David J. |date=1999 |title=Phylogenetic Systematics of Basal Perissodactyls |url=https://www.jstor.org/stable/4523976 |journal=Journal of Vertebrate Paleontology |volume=19 |issue=1 |pages=140–159 |bibcode=1999JVPal..19..140F |doi=10.1080/02724634.1999.10011129 |issn=0272-4634 |jstor=4523976|url-access=subscription }}</ref><ref>{{Citation |last=Tsoukala |first=Evangelia |title=The Fossil Record of Chalicotheres (Mammalia: Perissodactyla: Chalicotheriidae) in Greece |date=2022 |work=Fossil Vertebrates of Greece Vol. 2 |pages=501–517 |editor-last=Vlachos |editor-first=Evangelos |url=https://link.springer.com/10.1007/978-3-030-68442-6_15 |access-date=2024-08-22 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-68442-6_15 |isbn=978-3-030-68441-9|url-access=subscription }}</ref> A 2004 [[Cladistics|cladistic]] study alternatively recovered Ancylopoda as sister to all modern [[Perissodactyla|perissodactyls]] (which includes Equoidea and Ceratomorpha), with the [[Brontotheriidae|brontotheres]] [[Basal (phylogenetics)|basal]] to both.<ref>{{Cite journal |last1=Hooker |first1=J. J. |last2=Dashzeveg |first2=D. |date=2004 |title=The origin of chalicotheres (Perissodactyla, Mammalia) |journal=Palaeontology |language=en |volume=47 |issue=6 |pages=1363–1386 |bibcode=2004Palgy..47.1363H |doi=10.1111/j.0031-0239.2004.00421.x |issn=1475-4983 |s2cid=83720739 |doi-access=free}}</ref>

In their 1914 monograph on chalicotheres, Holland and Peterson listed three [[Subfamily|subfamilies]]: Moropodinae (''Ancylotherium'', ''Moropus'', and ''Nestoritherium''), Macrotheriinae (including ''[[Chalicotherium]]'', ''Circotherium'', and ''Macrotherium'') and [[Schizotheriinae]] (''[[Peratherium|Pernatherium]]'' and ''[[Schizotherium]]'').<ref name=":0" /> Macrotheriinae was subsequently synonymised with the existing [[Chalicotheriinae]]. Palaeontologist [[Arthur Smith Woodward]], in 1925, concurred with the system used by Holland and Peterson, and only altered the placements of a few genera.<ref name=":5">{{Cite journal |last1=Colbert |first1=Edwin Harris |author-link1=Edwin H. Colbert |last2=Brown |first2=Barnum |author-link2=Barnum Brown |date=1935 |title=Distributional and phylogenetic studies on Indian fossil mammals. 3, A classification of the Chalicotherioidea. |url=https://digitallibrary.amnh.org/items/7cfd1925-eb6f-449b-8bbe-60f9a8f71028 |journal=American Museum Novitates |issue=798}}</ref> [[William Diller Matthew]] instead split chalicotheres into just two subfamilies, Chalicotheriinae and [[Eomoropidae|Eomoropinae]]. The former was divided into two clades based on whether their teeth were [[Molar (tooth)|brachydont]] (short-crowned) or [[hypsodont]] (high-crowned): ''Moropus'' fell into the latter category.<ref name=":6">{{Cite journal |last=Matthew |first=William Diller |author-link=William Diller Matthew |date=1929 |title=Critical Observations Upon Siwalik Mammals |journal=Bulletin of the American Museum of Natural History |pages=516–524}}</ref> In 1935, [[Edwin H. Colbert]] retained this system, though divided Chalicotheriinae into the [[Tribe (biology)|tribes]] Chalicotheriini and Schizotheriini.<ref name=":5" /> Currently, they are both treated as tribes,<ref name="butler1965"/> and eomoropids have been removed from Chalicotheriidae entirely.<ref>{{Cite journal |last=Holbrook |first=L |date=1999 |title=The Phylogeny and Classification of Tapiromorph Perissodactyls (Mammalia) |url=https://doc.rero.ch/record/20950/files/PAL_E4153.pdf |journal=Cladistics |language=en |volume=15 |issue=3 |pages=331–350 |doi=10.1006/clad.1999.0107}}</ref><ref>{{Cite journal |last1=Missiaen |first1=Pieter |last2=Gingerich |first2=Philip D. |date=2012 |title=New Early Eocene Tapiromorph Perissodactyls from the Ghazij Formation of Pakistan, with Implications for Mammalian Biochronology in Asia |url=http://www.app.pan.pl/article/item/app20100093.html |journal=Acta Palaeontologica Polonica |language=en |volume=57 |issue=1 |pages=21–34 |doi=10.4202/app.2010.0093 |issn=0567-7920|hdl=1854/LU-3178691 |hdl-access=free }}</ref> ''Moropus'' is currently classified under Schizotheriinae.<ref>{{Cite journal |last1=Coombs |first1=Margery C. |last2=Hunt |first2=Robert M. |last3=Stepleton |first3=Ellen |last4=Albright |first4=L. Barry |last5=Fremd |first5=Theodore J. |date=2001-08-22 |title=Stratigraphy, chronology, biogeography, and taxonomy of early Miocene small chalicotheres in North America |url=http://www.tandfonline.com/doi/abs/10.1671/0272-4634%282001%29021%5B0607%3ASCBATO%5D2.0.CO%3B2 |journal=Journal of Vertebrate Paleontology |language=en |volume=21 |issue=3 |pages=607–620 |doi=10.1671/0272-4634(2001)021[0607:SCBATO]2.0.CO;2 |issn=0272-4634|url-access=subscription }}</ref>

==Description==
[[File:Moropus elatus life restoration.jpg|left|thumb|Size comparison between ''M.elatus'' and a human]]

Some species of ''Moropus'', such as ''M. elatus'', were among the largest chalicotheres,<ref name=":1" /> standing about {{convert|8|ft|m|abbr=on|order=flip}} tall at the shoulder and with a body weight around the size of a large rhinoceros.<ref name=":0" /> One ''Moropus'' specimen has an estimated body mass of {{Convert|1179|kg|lb|abbr=on}}.<ref>{{Cite journal |last1=Etienne |first1=Cyril |last2=Mallet |first2=Christophe |last3=Cornette |first3=Raphaël |last4=Houssaye |first4=Alexandra |date=2020-03-28 |title=Influence of mass on tarsus shape variation: a morphometrical investigation among Rhinocerotidae (Mammalia: Perissodactyla) |url=https://academic.oup.com/biolinnean/article/129/4/950/5727857 |journal=Biological Journal of the Linnean Society |volume=129 |issue=4 |pages=950–974 |doi=10.1093/biolinnean/blaa005 |issn=0024-4066}}</ref><ref>{{Cite book |title=Body size in mammalian paleobiology: estimation and biological implications |date=2005 |publisher=Cambridge University Press |isbn=978-0-521-01933-0 |editor-last=Damuth |editor-first=John |edition=1. paperb. version |location=Cambridge}}</ref> Smaller specimens have been described as being about the size of a tapir.<ref name=":0" /><ref>{{Cite book |last=Marsh |first=Othniel Charles |url=https://www.biodiversitylibrary.org/bibliography/30830 |title=Introduction and succession of vertebrate life in America. An address delivered before the American association for the advancement of science, at Nashville, Tenn., August 30, 1877 |date=1878 |publisher=Tuttle, Morehouse & Taylor, printers |location=New Haven, Conn}}</ref>

=== Skull ===
''Moropus''<nowiki/>' skull was fairly small compared to its body.<ref name=":7">{{Cite journal |last=Coombs |first=Margery Chalifoux |date=1983 |title=Large Mammalian Clawed Herbivores: A Comparative Study |url=https://www.jstor.org/stable/3137420 |journal=Transactions of the American Philosophical Society |volume=73 |issue=7 |pages=1–96 |doi=10.2307/3137420|jstor=3137420 |url-access=subscription }}</ref> It was narrow, and bore high [[Nasal bone|nasal bones]]. The snout had a spoon-shaped tip, a characteristic common to selective [[Browsing (herbivory)|browsers]]. It suggests the presence of mobile lips and possibly a long tongue.<ref name=":7" /> [[William Berryman Scott]] suggested that the tongue may have been used in conjunction with the upper lip to pull down branches.<ref>{{Cite book |last=Scott |first=William Berryman |author-link=William Berryman Scott |url=https://www.biodiversitylibrary.org/bibliography/54974 |title=A history of land mammals in the Western Hemisphere; illustrated with 32 plates and more than 100 drawings |date=1913 |publisher=Macmillan |location=New York}}</ref> The lower [[Incisor|incisors]] protruded forwards, and the [[premaxilla]] is [[Toothlessness|toothless]], similar to in modern [[Ruminant|ruminants]]. This would have formed a cropping mechanism for processing vegetation. There was a [[diastema]] (gap) separating the incisors from the [[cheek teeth]], which would have allowed the tongue to extrude from the mouth.<ref name=":7" /> The [[maxilla]] was similar to that of modern horses (''[[Equus (genus)|Equus]]'').<ref name=":0" /> Some specimens (or species) ''Moropus'' did not have a [[sagittal crest]],<ref name=":2" /> while others did, even as juveniles.<ref name=":0" /> 

=== Dentition ===
''Moropus'' had incisors only on the lower jaw.<ref name=":8">{{Cite journal |last=Coombs |first=Margery Chalifoux |date=1978 |title=A Premaxilla of Moropus elatus Marsh, and Evolution of Chalicotherioid Anterior Dentition |url=https://www.jstor.org/stable/1303796 |journal=Journal of Paleontology |volume=52 |issue=1 |pages=118–121 |jstor=1303796 |issn=0022-3360}}</ref> The cheek teeth (the [[Premolar|premolars]] and [[Molar (tooth)|molars]]) were robust, covered in thick [[Tooth enamel|enamel]], and strongly rooted. The first upper premolar is absent, like other chalicotheres. The second upper premolar was triangular, with the protocone and tritocone ([[Cusp (anatomy)|cusps]]) having fused into a single structure, mostly comprising the former. The third upper premolar is more quadrate in shape, and has one tubercle rather than two. The fourth upper premolar is slightly larger but otherwise very similar.<ref name=":0" /> The lower incisors, of which there were three on each side,<ref name=":0" /> are procumbent (protruding), spatulate, and were separated from the cheek teeth by a long diastema.<ref name=":8" /> The first upper molar is very enlarged, the second is one-fifth longer, and the third is only slightly larger. All three are roughly the same in terms of overall structure. The second lower premolar is highly reduced. Third is molariform (molar-like), in a similar fashion to the brontothere ''[[Megacerops]]''. The first lower molar is considerably wider than the fourth lower premolar, though they are otherwise quite similar, with the exception that the [[Glossary of mammalian dental topography|hypoconid]] is more well-developed and the [[Cingulum (tooth)|cingulum]] is less so. The second lower molar is longer, and has a more prominent cingulum. The third lower molar lacks its third lobe, similar to other chalicotheres.<ref name=":0" />

=== Postcranial skeleton ===
''Moropus''<nowiki/>' neck was somewhat like that of a modern horse, albeit considerably stockier.<ref name=":0" /> All of ''Moropus''<nowiki/>' [[Cervical vertebrae|cervical]] (neck) [[Vertebra|vertebrae]] were somewhat elongated, and the neck was long enough that, when drinking, ''Moropus'' would have to splay its forelimbs to reach the ground level, as in modern [[Giraffe|giraffes]]. This, and the fact that the [[Anatomical terms of location|dorsal]] musculature of the neck appears to have been stronger than the [[Anatomical terms of location|ventral]] musculature, suggest that ''Moropus'' held its neck obliquely upright.<ref name=":7" /> As in other [[chalicothere]]s, ''Moropus'' differed from typical ungulates in having large claws, rather than hooves, on the feet. Three large, highly compressed claws were present on each of the front feet, supported inside by fissured bony [[Phalanx bone|phalanges]]. As with all schizotheriines, the articulation of the [[phalanges|phalangeal]] (finger) bones shows that ''Moropus'' could retract its claws enough to walk smoothly with the front feet in a normal digitigrade stance, lifting the claws by [[Anatomical terms of motion|hyperextension]]. ''Moropus'' was likely more heavily quadrupedal than ''Chalicotherium''. However, while not as extreme as in ''Chalicotherium'', ''Moropus''<nowiki/>' [[pelvis]] still bore some adaptations for bipedal stance, such as a long [[ischium]], and changes in the structure of the hindfoot (i.e. the shortening and widening of the [[Talus bone|astragalus]]) to increase its weight-bearing capabilities without sacrificing limb length.<ref name=":7" />

== Palaeobiology ==
[[File:Moropus oregonensis.jpg|thumb|Life restoration of a [[Browsing (herbivory)|browsing]] ''M. oregonensis'']]

=== Feeding and diet ===
The spoon-shaped snout tip of ''Moropus'' suggests that it was a browser.<ref name=":7" /> It was suggested by William Diller Matthew that ''Moropus'' used its claws to dig for buried plant matter and water sources,<ref name=":6" /> though as it did not live in an arid environment, this is unlikely.<ref name=":7" /> Russian palaeontologist Alexey Borissiak suggested, based on ''[[Borissiakia]]'' from Kazakhstan, that schizotheriines may have fed bipedally, wedging their front claws into tree bark for support. The middle claw could be driven directly into the bark, while the first and third could be freely moved as necessary.<ref>{{Cite journal |last=Borissiak |first=Alexey A. |date=1945 |title=The chalicotheres as a biological type |url=https://ajsonline.org/api/v1/articles/61288-the-chalicotheres-as-a-biological-type.pdf |journal=Amer. Jour. Sci |volume=243 |issue=12 |pages=667–679|doi=10.2475/ajs.243.12.667 |pmid=21004238 |bibcode=1945AmJS..243..667B }}</ref> In 1943, Swiss palaeontologist Samuel Schaub suggested that the related ''[[Ancylotherium]]'' used its forelimbs to pull down vegetation,<ref>{{Cite journal |last=Schaub |first=Samuel |date=1943 |title=Die Vorderextremitat von Ancylotherium pentelicum Gaudry und Lartet |journal=Schweizerischen Palaeont. Abhandl |volume=64 |pages=1–36}}</ref> much as in chalicotheriines.<ref name=":7" />

=== Sexual dimorphism ===
There has been some debate over whether ''Moropus'' was [[Sexual dimorphism|sexually dimorphic]]. The matter was discussed by Olof August Peterson and William Jacob Holland in their monograph, in reference to two different mature size groups that had been noted. The larger one was ''M. elatus'', and the other was, at the time, considered ''M. petersoni''. Larger individuals possessed small sagittal crests, whereas smaller individuals did not (and instead retained independent [[Supraorbital ridge|supraorbital ridges]]), though noted this could be due to sexual dimorphism. They supposed that, if they were females, the smaller specimens would have a larger [[pelvic cavity]] with larger [[Foramen|foramina]] for blood supply, which is not observed. Based on the relative subtetly of these differences, which did not, to them, indicate sexual dimorphism, the smaller morph was decided to probably be separate, and ''Moropus petersoni'' was retained as a taxon.<ref name=":0" /> However, Margery Chalifoux Coombs suggested that there was, in reality, no reason to assume that sexual dimorphism was absent, and opted to sink ''M. petersoni'' into ''M. elatus''. She suggested that "''M. petersoni''", being smaller, may have represented the female of ''M. elatus''. Further, she noted that there were cases of possible sexual dimorphism throughout Chalicotheriidae, and that there would be a strong precedent for it.<ref name=":3" />

{{Portal|Paleontology}}

==References==
{{Reflist}}
*

{{Perissodactyla Genera|T.}}
{{Ancylopoda}}
{{Taxonbar|from=Q133086}}

[[Category:Schizotheriinae]]
[[Category:Miocene Perissodactyla]]
[[Category:Miocene mammals of North America]]
[[Category:White River Fauna]]
[[Category:Miocene genus first appearances]]
[[Category:Fossil taxa described in 1877]]
[[Category:Taxa named by Othniel Charles Marsh]]