Editing Litopterna

{{Short description|Extinct order of hoofed mammals}}
{{Automatic taxobox
| fossil_range = {{Fossil range|Paleocene|Holocene}}
| image = Macrauchenia patachonica Skeletal (cropped).png
| image_caption = Skeleton of  ''[[Macrauchenia]]'' ([[Macraucheniidae]])
| image2 = Reports of the Princeton University Expeditions to Patagonia, 1896-1899. J. B. Hatcher in charge (1901) (14563211299).jpg
| image2_caption = Skeleton of ''[[Diadiaphorus]]'' ([[Proterotheriidae]])
| taxon = Litopterna
| authority = [[Florentino Ameghino|Ameghino]] 1889
| subdivision_ranks = Subgroups
| subdivision = *{{extinct}}[[Didolodontidae]]?
*{{extinct}}[[Notonychopidae]]
*{{extinct}}[[Protolipternidae]]
*{{extinct}}[[Sparnotheriodontidae]]
*{{extinct}}[[Indaleciidae]]
*{{extinct}}'''Lopholipterna'''
**{{extinct}}'''Proterotherioidea'''
***{{extinct}}[[Proterotheriidae]]
**{{extinct}}'''Macrauchenioidea'''
***{{extinct}}[[Adianthidae]]
***{{extinct}}[[Macraucheniidae]]
}}

'''Litopterna''' (from {{langx|grc|λῑτή πτέρνα}} "smooth heel") is an [[extinction|extinct]] order of [[South American native ungulates]] that lived from the [[Paleocene]] to the [[Pleistocene]]-[[Holocene]] around 62.5 million to 12,000 years ago (or possibly as late as 3,500 years ago), and were also present in Antarctica during the [[Eocene]]. They represent the second most diverse group of South American ungulates after [[Notoungulata]].<ref name="Croft-2020">{{Cite journal |last1=Croft |first1=Darin A. |last2=Gelfo |first2=Javier N. |last3=López |first3=Guillermo M. |date=2020-05-30 |title=Splendid Innovation: The Extinct South American Native Ungulates |url=https://www.annualreviews.org/doi/10.1146/annurev-earth-072619-060126 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=48 |issue=1 |pages=259–290 |doi=10.1146/annurev-earth-072619-060126 |bibcode=2020AREPS..48..259C |s2cid=213737574 |issn=0084-6597|url-access=subscription }}</ref> It is divided into nine families, with [[Proterotheriidae]] and [[Macraucheniidae]] being the most diverse and last surviving families.<ref name="Carrillo-2023">{{Cite journal |last1=Carrillo |first1=Juan D. |last2=Suarez |first2=Catalina |last3=Benites-Palomino |first3=Aldo Marcelo |last4=Vanegas |first4=Andrés |last5=Link |first5=Andrés |last6=Rincón |first6=Aldo F. |last7=Luque |first7=Javier |last8=Cooke |first8=Siobhán B. |last9=Tallman |first9=Melissa |last10=Billet |first10=Guillaume |date=2023-08-31 |title=New remains of Neotropical bunodont litopterns and the systematics of Megadolodinae (Mammalia: Litopterna) |journal=Geodiversitas |volume=45 |issue=15 |doi=10.5252/geodiversitas2023v45a15 |s2cid=261638835 |issn=1280-9659}}</ref>

== Diversity ==
[[File:Reports of the Princeton University Expeditions to Patagonia, 1896-1899. J. B. Hatcher in charge (1901) (14749571352).jpg|left|thumb|Skeleton of ''[[Theosodon]]'' (Macraucheniidae)]]
[[File:Thoatheriumknight.jpg|left|thumb|Historic life restoration of ''[[Thoatherium]]'' (Proterotheriidae)]]
The body forms of many litopterns, notably in the limb and skull structure, are broadly similar to those of living [[ungulate]]s, unlike other [[South American native ungulate]] groups, which are often strongly divergent from living ungulates.<ref name="Croft-2021" /> Paleocene and Eocene litopterns generally had small body masses, with ''[[Protolipterna]]'' ([[Protolipternidae]]) estimated to have had a body mass of {{Convert|0.5-1.5|kg|lb|abbr=}}, though the Eocene [[Sparnotheriodontidae|sparnotheriodontids]] were considerably larger, with estimated body masses of around {{Convert|400|kg|lb|abbr=}}. Most proterotheriids had body masses of around {{Convert|15 to 80|kg|lb}} while many macraucheniids had body masses of around {{Convert|80–120|kg|lb}}. Some of the last macraucheniids like ''[[Macrauchenia]]'' were considerably larger, with body masses around a ton.<ref name="Croft-2020" /> [[Adianthidae]] generally had small body masses, with members of the genus ''[[Adianthus]]'' estimated to weigh {{Convert|7.4-20|kg|lb}}. Members of the proterotheriid subfamily Megadolodinae are noted for having [[bunodont]] (rounded cusp) molar teeth, which is largely unique to litopterns among South American native ungulates.<ref name="Carrillo-2023" /><ref name="Croft-2020" /> Litopterns of the mid-late Cenozoic had hinge-like limb joints and [[Hoof|hooves]] similar to those of modern ungulates, with the weight being supported on three toes in macraucheniids and one in proterotheriids, with the protherotheriid ''[[Thoatherium]]'' developing greater toe reduction than that present in living horses.<ref name="Croft-2020" /> Macraucheniids had long necks and limbs.<ref name="Schmidt-2014">{{Cite journal |last1=Schmidt |first1=Gabriela I. |last2=Ferrero |first2=Brenda S. |date=2014-07-29 |title=Taxonomic reinterpretation of Theosodon hystatus Cabrera and Kraglievich, 1931 (Litopterna, Macraucheniidae ) and phylogenetic relationships of the family |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2014.837393 |journal=Journal of Vertebrate Paleontology |language=en |volume=34 |issue=5 |pages=1231–1238 |doi=10.1080/02724634.2014.837393 |bibcode=2014JVPal..34.1231S |hdl=11336/18953 |s2cid=86091386 |issn=0272-4634|hdl-access=free }}</ref> 

Members of the macraucheniid subfamily Macraucheniinae saw the progressive migration of the nasal opening to the top of the skull,<ref>{{Cite journal |last1=Forasiepi |first1=Analía M. |last2=MacPhee |first2=Ross D. E. |last3=Del Pino |first3=Santiago Hernández |last4=Schmidt |first4=Gabriela I. |last5=Amson |first5=Eli |last6=Grohé |first6=Camille |date=2016-06-22 |title=Exceptional Skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) From the Late Miocene of Argentina: Anatomy, Systematics, and Paleobiological Implications |url=http://www.bioone.org/doi/10.1206/0003-0090-404.1.1 |journal=Bulletin of the American Museum of Natural History |language=en |volume=404 |pages=1–76 |doi=10.1206/0003-0090-404.1.1 |s2cid=89219979 |issn=0003-0090}}</ref> which was often historically suggested to indicate the presence of a trunk, though other authors have suggested that a [[moose]]-like prehensile lip,<ref>{{Cite journal |last1=Moyano |first1=Silvana Rocio |last2=Giannini |first2=Norberto Pedro |date=November 2018 |title=Cranial characters associated with the proboscis postnatal-development in Tapirus (Perissodactyla: Tapiridae) and comparisons with other extant and fossil hoofed mammals |url=https://linkinghub.elsevier.com/retrieve/pii/S0044523118301001 |journal=Zoologischer Anzeiger |language=en |volume=277 |pages=143–147 |doi=10.1016/j.jcz.2018.08.005|s2cid=92143497 |doi-access=free |hdl=11336/86349 |hdl-access=free }}</ref> or a [[Saiga antelope|saiga]]-like nose to filter dust<ref>{{Cite journal |last1=Blanco |first1=R. Ernesto |last2=Jones |first2=Washington W. |last3=Yorio |first3=Lara |last4=Rinderknecht |first4=Andrés |date=October 2021 |title=Macrauchenia patachonica Owen, 1838: Limb bones morphology, locomotory biomechanics, and paleobiological inferences |url=https://linkinghub.elsevier.com/retrieve/pii/S0016699521000425 |journal=Geobios |language=en |volume=68 |pages=61–70 |bibcode=2021Geobi..68...61B |doi=10.1016/j.geobios.2021.04.006|url-access=subscription }}</ref> are more likely.

{{Multiple image
| total_width       = 400
| image1            = Macraucheniidae skulls.jpg
| image2            = Macraucheniidae skulls 2.jpg
| footer            = Skulls of the macraucheniids (A) ''[[Theosodon]]'', (B) ''[[Scalabrinitherium]]'', (C) ''[[Macrauchenia]]'', portraying how the nasal bones shifted backwards on the skull, with the nasal opening following suit.
| align             = center
}}

== Ecology ==
Litopterns were likely [[hindgut fermenters]].<ref name="Croft-2021">{{Cite journal |last1=Croft |first1=Darin A. |last2=Lorente |first2=Malena |date=2021-08-17 |editor-last=Smith |editor-first=Thierry |title=No evidence for parallel evolution of cursorial limb adaptations among Neogene South American native ungulates (SANUs) |journal=PLOS ONE |language=en |volume=16 |issue=8 |pages=e0256371 |doi=10.1371/journal.pone.0256371 |issn=1932-6203 |pmc=8370646 |pmid=34403434 |doi-access=free }}</ref> At least some macraucheniids like ''Macrauchenia'' are suggested to have been mixed feeders feeding on both browse and grass.<ref>{{Cite journal |last1=de Oliveira |first1=Karoliny |last2=Asevedo |first2=Lidiane |last3=Calegari |first3=Marcia R. |last4=Gelfo |first4=Javier N. |last5=Mothé |first5=Dimila |last6=Avilla |first6=Leonardo |date=August 2021 |title=From oral pathology to feeding ecology: The first dental calculus paleodiet study of a South American native megamammal |url=https://linkinghub.elsevier.com/retrieve/pii/S0895981121001280 |journal=Journal of South American Earth Sciences |language=en |volume=109 |pages=103281 |doi=10.1016/j.jsames.2021.103281|bibcode=2021JSAES.10903281D |s2cid=233678648 |url-access=subscription }}</ref> Sparnotheriodontids are suggested to have been [[Browsing (herbivory)|browsers]].<ref>{{Cite journal |last1=Bond |first1=M. |last2=Reguero |first2=M. A. |last3=Vizcaíno |first3=S. F. |last4=Marenssi |first4=S. A. |date=January 2006 |title=A new 'South American ungulate' (Mammalia: Litopterna) from the Eocene of the Antarctic Peninsula |url=https://www.lyellcollection.org/doi/10.1144/GSL.SP.2006.258.01.12 |journal=Geological Society, London, Special Publications |language=en |volume=258 |issue=1 |pages=163–176 |doi=10.1144/GSL.SP.2006.258.01.12 |issn=0305-8719|url-access=subscription }}</ref> Some proterotheriids are suggested to have been browsers,<ref>{{Cite journal |last1=Morosi |first1=Elizabeth |last2=Ubilla |first2=Martin |date=2019-02-07 |title=Dietary and palaeoenvironmental inferences in Neolicaphrium recens Frenguelli, 1921 (Litopterna, Proterotheriidae) using carbon and oxygen stable isotopes (Late Pleistocene; Uruguay) |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2017.1355914 |journal=Historical Biology |language=en |volume=31 |issue=2 |pages=196–202 |doi=10.1080/08912963.2017.1355914 |s2cid=133673644 |issn=0891-2963|url-access=subscription }}</ref> while some members proterotheriid subfamily Megadolodinae like ''[[Megadolodus]]'' have been suggested to have been [[Omnivore|omnivorous]] with at least part of their diet consisting of hard fruit.<ref name="Carrillo-2023" />

== Evolutionary history ==
Litopterna, like other "South American native ungulates" is thought to have originated from groups of archaic "[[condylarth]]s" that migrated from North America.<ref name="Croft-2020" /> Sequencing of the [[collagen]] [[proteome]] and [[mitochondrial genome]] of ''Macrauchenia'' has revealed that litopterns are true ungulates, sharing a common ancestor with [[Notoungulata]], and with their closest living relatives being [[Perissodactyla]] (the group containing living [[Equidae|equines]], [[rhinoceros]] and [[tapirs]]) as part of the clade [[Panperissodactyla]], with the split from Perissodactyla being estimated at around 66 million years ago.<ref name="WelkerCollins2015">{{Cite journal |last1=Welker |first1=Frido |last2=Collins |first2=Matthew J. |last3=Thomas |first3=Jessica A. |last4=Wadsley |first4=Marc |last5=Brace |first5=Selina |last6=Cappellini |first6=Enrico |last7=Turvey |first7=Samuel T. |last8=Reguero |first8=Marcelo |last9=Gelfo |first9=Javier N. |date=March 18, 2015 |title=Ancient proteins resolve the evolutionary history of Darwin/'s South American ungulates |url=http://eprints.whiterose.ac.uk/91438/1/Welker_postprint.docx |journal=[[Nature (journal)|Nature]] |volume=522 |issue=7554 |pages=81–84 |bibcode=2015Natur.522...81W |doi=10.1038/nature14249 |issn=1476-4687 |pmid=25799987 |s2cid=4467386|hdl=11336/14769 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Westbury |first1=Michael |last2=Baleka |first2=Sina |last3=Barlow |first3=Axel |last4=Hartmann |first4=Stefanie |last5=Paijmans |first5=Johanna L.A. |last6=Kramarz |first6=Alejandro |last7=Forasiepi |first7=Analía M |last8=Bond |first8=Mariano |last9=Gelfo |first9=Javier N. |last10=Reguero |first10=Marcelo A. |last11=López-Mendoza |first11=Patricio |last12=Taglioretti |first12=Matias |last13=Scaglia |first13=Fernando |last14=Rinderknecht |first14=Andrés |last15=Jones |first15=Washington |date=2017-06-27 |title=A mitogenomic timetree for Darwin's enigmatic South American mammal Macrauchenia patachonica |journal=Nature Communications |language=en |volume=8 |issue=1 |page=15951 |doi=10.1038/ncomms15951 |issn=2041-1723 |pmc=5490259 |pmid=28654082|bibcode=2017NatCo...815951W }}</ref> The relationship of Litopterna to other South American native ungulate groups is uncertain, though it may be closely related to the "condylarth" group [[Didolodontidae]].<ref name="Croft-2020" /> The earliest litopterns appeared during the early [[Paleocene]], around 62.5 million years ago.<ref>{{Cite journal |last1=Püschel |first1=Hans P |last2=Shelley |first2=Sarah L |last3=Williamson |first3=Thomas E |last4=Perini |first4=Fernando A |last5=Wible |first5=John R |last6=Brusatte |first6=Stephen L |date=2024-09-02 |title=A new dentition-based phylogeny of Litopterna (Mammalia: Placentalia) and 'archaic' South American ungulates |url=https://academic.oup.com/zoolinnean/article/doi/10.1093/zoolinnean/zlae095/7750676 |journal=Zoological Journal of the Linnean Society |language=en |volume=202 |issue=1 |doi=10.1093/zoolinnean/zlae095 |issn=0024-4082|doi-access=free }}</ref>

Aside from South America, sparnotheriodontids are also known from the [[Eocene]] aged [[La Meseta Formation]] in the Antarctic Peninsula, representing the only record of litopterns on the Antarctic continent. Litopterns declined during the [[Pliocene]] and [[Pleistocene]], likely as a result of climatic change and competition with recently immigrated North American ungulates who arrived as part of the [[Great American Interchange|Great American interchange]], following the connection of the previously isolated North and South America via the [[Isthmus of Panama]].<ref name="Croft-2020" /> ''Macrauchenia,'' ''[[Xenorhinotherium]]'' (Macraucheniidae) and ''[[Neolicaphrium]]'' (Proterotheriidae) were the last surviving genera of litopterns. All became extinct at the end of the [[Late Pleistocene]] around 12,000 years ago as part of the [[Late Pleistocene extinctions|end-Pleistocene extinction event]], along with most other large mammals in the Americas, co-inciding with the arrival of the first humans to the continent.<ref name="Schmidt-2014" /> A study in 2025 suggested that ''Xenorhinotherium'' may have survived until the late Holocene based on a specimen [[Radiocarbon dating|radiocarbon dated]] to 3,493–4,217 years [[Radiocarbon calibration|cal.]] [[Before Present]] (BP).<ref>{{Cite journal |last=Cortes Faria |first=Fábio Henrique |last2=de Souza Carvalho |first2=Ismar |last3=Ismael de Araújo-Júnior |first3=Hermínio |last4=Ximenes |first4=Celso Lira |last5=Facincani |first5=Edna Maria |date=2025-01-17 |title=3,500 years BP: The last survival of the mammal megafauna in the Americas |url=https://www.sciencedirect.com/science/article/abs/pii/S089598112500029X |journal=Journal of South American Earth Sciences |volume=153 |pages=105367 |doi=10.1016/j.jsames.2025.105367 |issn=0895-9811|url-access=subscription }}</ref> It is possible that hunting had a causal role in their extinction.<ref name="SDWebb">{{cite journal|last=Webb|first=S. D.|year=1976|title=Mammalian Faunal Dynamics of the Great American Interchange|journal=Paleobiology|volume=2|issue=3|pages=220–234|doi=10.1017/S0094837300004802|jstor=2400220|bibcode=1976Pbio....2..220W |s2cid=251050063 }}</ref><ref name="Marshal1990">{{cite journal|last1=Marshall|first1=L. G.|last2=Cifelli|first2=R. L.|date=1990|title=Analysis of changing diversity patterns in Cenozoic land mammal age faunas, South America|url=http://palaeovertebrata.com/Articles/sendFile/284/published_article|journal=Palaeovertebrata|volume=19|pages=169–210|access-date=2018-10-08}}</ref><ref name="SDWebb2">{{cite journal|last=Webb|first=S. D.|year=1991|title=Ecogeography and the Great American Interchange|journal=Paleobiology|volume=17|issue=3|pages=266–280|doi=10.1017/S0094837300010605|jstor=2400869|bibcode=1991Pbio...17..266W |s2cid=88305955 }}</ref><ref name="Croft-2020" />

== Classification ==
{{One source|section|date=April 2022}}
* Order '''Litopterna'''<ref>{{Cite web |title=PBDB |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=43467 |access-date=2022-04-29 |website=paleobiodb.org}}</ref>
** ''[[Proacrodon]]''
** Family [[Protolipternidae]] 
*** ''[[Asmithwoodwardia]]''
*** ''[[Miguelsoria]]''
*** ''[[Protolipterna]]''
** Family [[Indaleciidae]]
*** [[File:Adiantoides leali.jpg|thumb|''[[Adiantoides|Adiantoides leali]]'']][[File:Cramauchenia insolita.jpg|thumb|''[[Cramauchenia|Cramauchenia normalis]]'']][[File:Theosodon patagonica skull (cropped).jpg|thumb|''[[Theosodon|Theosodon patagonica]]'']][[File:Macrauchenia skeleton at AMNH.jpg|thumb|''[[Macrauchenia]]'']][[File:Xenorhinotherium bahiensis, MHNT 02 (cropped).jpg|thumb|''[[Xenorhinotherium|Xenorhinotherium bahiensis]]'']]''[[Adiantoides]]''
*** ''[[Indalecia]]''
** Family [[Sparnotheriodontidae]]
*** ''[[Phoradiadius]]''
*** ''[[Notiolofos]]''
*** ''[[Sparnotheriodon]]''
*** ''[[Victorlemoinea]]''
** Family [[Amilnedwardsiidae]]
*** ''[[Amilnedwardsia]]''
*** ''[[Ernestohaeckelia]]''
*** ''[[Rutimeyeria]]''
** Family [[Notonychopidae]]
*** ''[[Notonychops]]''
*** ''[[Requisia]]''
** Superfamily [[Macrauchenioidea]]
*** Family [[Adianthidae]]
**** ''[[Proectocion]]''
**** [[Adianthinae]]
***** ''[[Adianthus]]''
***** ''[[Proadiantus]]''
***** ''[[Proheptaconus]]''
***** ''[[Thadanius]]''
***** ''[[Tricoelodus]]''
*** Family [[Macraucheniidae]]
**** ''[[Llullataruca]]''
**** Subfamily [[Cramaucheniinae]]
***** ''[[Coniopternium]]''
***** ''[[Caliphrium]]''
***** ''[[Cramauchenia]]''
***** ''[[Phoenixauchenia]]''
***** ''[[Polymorphis]]''
***** ''[[Pternoconius]]''
***** ''[[Theosodon]]''
**** [[Subfamily]] [[Macraucheniinae]]
***** ''[[Cullinia]]''
***** ''[[Huayqueriana]]''
***** ''[[Macrauchenia]]''
***** ''[[Macraucheniopsis]]''
***** ''[[Oxyodontherium]]''
***** ''[[Paranauchenia]]''
***** ''[[Promacrauchenia]]''
***** ''[[Scalabrinitherium]]''
***** ''[[Windhausenia]]''
***** ''[[Xenorhinotherium]]''
** Superfamily [[Proterotherioidea]]
*** Family [[Proterotheriidae]]
**** [[File:Anisolophus floweri.jpg|thumb|''[[Anisolophus|Anisolophus floweri]]'']][[File:Diadiaphorus majusculus (cropped).jpg|thumb|''[[Diadiaphorus|Diadiaphorus majusculus]]'']][[File:Thoatherium crepidatum skull cast (cropped).jpg|thumb|''[[Thoatherium|Thoatherium crepidatum]]'']]''[[Anisolambda]]''
**** ''[[Anisolophus]]''
**** ''[[Brachytherium]]''
**** ''[[Diadiaphorus]]''
**** ''[[Diplasiotherium]]''
**** ''[[Eoauchenia]]''
**** ''[[Eolicaphrium]]''
**** ''[[Epecuenia]]''
**** ''[[Epitherium]]''
**** ''[[Guilielmofloweria]]''
**** ''[[Heteroglyphis]]''
**** ''[[Lambdaconus]]''
**** ''[[Lambdaconops]]''
**** ''[[Mesolicaphrium]]''
**** ''[[Neobrachytherium]]''
**** ''[[Neodolodus]]''
**** ''[[Neolicaphrium]]''
**** ''[[Olisanophus]]''
**** ''[[Paramacrauchenia]]''
**** ''[[Paranisolambda]]''
**** ''[[Picturotherium]]''
**** ''[[Prolicaphrium]]''
**** ''[[Promylophis]]''
**** ''[[Proterotherium]]''
**** ''[[Protheosodon]]''
**** ''[[Pseudobrachytherium]]''
**** ''[[Tetramerorhinus]]''
**** ''[[Thoatherium]]''
**** ''[[Thoatheriopsis]]''
**** ''[[Villarroelia]]''
**** ''[[Uruguayodon]]''
**** ''[[Wainka]]''
**** ''[[Xesmodon]]''
**** [[Megadolodinae]]
***** ''[[Bounodus]]''
***** ''[[Megadolodus]]''

== References ==
{{Reflist}}

== Further reading ==
* {{Cite book
 | last1 = McKenna | first1 = Malcolm C
 | last2 = Bell | first2 = Susane K
 | title = Classification of Mammals Above the Species Level
 | year = 1997 | publisher = Columbia University Press | location = New York
 | isbn = 978-0-231-11013-6}}

== External links ==
{{Commons category}}
* [http://www.rau.edu.uy/uruguay/iconos/macrauke-.gif An artist's rendition] of a [[Macrauchenia]], a representative genus of the Litopterna. Retrieved from the [[Red Académica Uruguaya]] [http://www.rau.edu.uy/uruguay/historia/megafauna.htm megafauna page]
{{Meridiungulata|L.|state=collapsed}}
{{Taxonbar|from=Q132153}}

[[Category:Litopterns| ]]
[[Category:Panperissodactyla]]
[[Category:Danian first appearances]]
[[Category:Holocene extinctions]]
[[Category:Fossil taxa described in 1889]]
[[Category:Taxa named by Florentino Ameghino]]