Editing Megatherium (section)

== Ecology ==
[[File:Pleistocene SA.jpg|thumb|Upright ''Megatherium americanum'' in an open landscape alongside two individuals of the [[glyptodont]] ''[[Glyptodon]].'']]
Remains of ''Megatherium americanum'' have been found in low elevation areas to the east of the Andes mountains in northern [[Patagonia]], the [[Pampas]] and adjacent areas in what is now northern Argentina, Uruguay, Paraguay, southern Bolivia and [[Rio Grande do Sul]] in southern Brazil.<ref name=":10" /> ''Megatherium americanum'' inhabited [[Temperate climate|temperate]], [[Arid climate|arid]]-to [[Semi-arid climate|semi arid]] open habitats.<ref>{{Cite journal |last1=Varela |first1=Luciano |last2=Tambusso |first2=P. Sebastián |last3=Patiño |first3=Santiago J. |last4=Di Giacomo |first4=Mariana |last5=Fariña |first5=Richard A. |date=December 2018 |title=Potential Distribution of Fossil Xenarthrans in South America during the Late Pleistocene: co-Occurrence and Provincialism |url=http://link.springer.com/10.1007/s10914-017-9406-9 |journal=Journal of Mammalian Evolution |language=en |volume=25 |issue=4 |pages=539–550 |doi=10.1007/s10914-017-9406-9 |issn=1064-7554}}</ref> During the [[Last Glacial Period]], the Pampas was generally drier than it is at present with many areas exhibiting a [[steppe]]-like environment dominated by grass, with some areas of woodland.<ref name=":10" />

Although some authors have suggested that ''Megatherium'' was an omnivore,<ref name=":12">{{Cite journal |last1=Fariña |first1=R. A. |last2=Blanco |first2=R. E. |date=1996-12-22 |title=Megatherium, the stabber |url=https://royalsocietypublishing.org/doi/10.1098/rspb.1996.0252 |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |language=en |volume=263 |issue=1377 |pages=1725–1729 |doi=10.1098/rspb.1996.0252 |pmid=9025315 |issn=0962-8452}}</ref> isotopic analysis has supported an entirely herbivorous diet for ''Megatherium''.<ref>{{Cite journal |last1=Bocherens |first1=Hervé |last2=Cotte |first2=Martin |last3=Bonini |first3=Ricardo A. |last4=Straccia |first4=Pablo |last5=Scian |first5=Daniel |last6=Soibelzon |first6=Leopoldo |last7=Prevosti |first7=Francisco J. |date=August 2017 |title=Isotopic insight on paleodiet of extinct Pleistocene megafaunal Xenarthrans from Argentina |url=https://linkinghub.elsevier.com/retrieve/pii/S1342937X16304944 |journal=Gondwana Research |language=en |volume=48 |pages=7–14 |doi=10.1016/j.gr.2017.04.003|bibcode=2017GondR..48....7B |hdl=11336/56592 }}</ref> ''Megatherium americanum'' is suggested to have been a [[Browsing (herbivory)|browser]] that was a selective feeder on the foliage, twigs and fruits of trees and shrubs.<ref name=":7" /><ref>Bargo, M. S., & Vizcaíno, S. F. (2008). Paleobiology of Pleistocene Ground Sloths (Xenarthra, Tardigrada): Biomechanics, Morphogeometry and Ecomorphology Applied to the Masticatory Apparatus. ''Ameghiniana'', ''45''(1), 175–196.</ref> The sharp cusps of the teeth served to shear plant material.<ref name=":13" /> ''Megatherium'' is widely thought to have been able to adopt a bipedal posture to use its forelimbs to grasp vegetation, though whether it was capable of moving in this posture is uncertain.<ref>{{Cite journal |last1=Milne |first1=Nick |last2=Toledo |first2=Nestor |last3=Vizcaíno |first3=Sergio F. |date=September 2012 |title=Allometric and Group Differences in the Xenarthran Femur |url=http://link.springer.com/10.1007/s10914-011-9171-0 |journal=Journal of Mammalian Evolution |language=en |volume=19 |issue=3 |pages=199–208 |doi=10.1007/s10914-011-9171-0 |hdl=11336/193251 |issn=1064-7554}}</ref> Analysis of injuries on the clavicles of ''M. americanum'' individuals suggests that the species probably habitually moved in a quadrupedal posture and assumed a bipedal posture next to trees to feed on high-growing leaves, likely using its forelimbs to brace itself against the tree trunk, as well as to pull down higher branches within reach of its prehensile lip.<ref name=":11">{{Cite journal |last1=Chichkoyan |first1=Karina V. |last2=Villa |first2=Chiara |last3=Winkler |first3=Viola |last4=Manuelli |first4=Luigi |last5=Acuña Suarez |first5=Gabriel E. |date=2022-12-16 |title=Paleopathologies of the Clavicles of the Giant Ground Sloth Megatherium americanum (Mammalia, Xenarthra) from the Pleistocene of the Pampean Region (Argentina) |url=https://bioone.org/journals/ameghiniana/volume-59/issue-6/AMGH.15.10.2022.3509/Paleopathologies-of-the-Clavicles-of-the-Giant-Ground-Sloth-Megatherium/10.5710/AMGH.15.10.2022.3509.full |journal=Ameghiniana |volume=59 |issue=6 |doi=10.5710/AMGH.15.10.2022.3509 |issn=0002-7014}}</ref> Isotopic analysis suggests that some individuals of ''M. americanum'' at certain times and places also consumed grass.<ref>{{Cite journal |last1=Sanz-Pérez |first1=Dánae |last2=Hernández Fernández |first2=Manuel |last3=Tomassini |first3=Rodrigo L. |last4=Montalvo |first4=Claudia I. |last5=Beilinson |first5=Elisa |last6=Gasparini |first6=Germán M. |last7=Domingo |first7=Laura |date=June 2022 |title=The Pampean region (Argentina) underwent larger variation in aridity than in temperature during the late Pleistocene: New evidence from the isotopic analysis of mammalian taxa |url=https://linkinghub.elsevier.com/retrieve/pii/S027737912200186X |journal=Quaternary Science Reviews |language=en |volume=286 |pages=107555 |doi=10.1016/j.quascirev.2022.107555|bibcode=2022QSRv..28607555S }}</ref> The smaller ''Megatherium tarijense'' has been suggested to have had a mixed feeding-browsing diet.<ref>{{Cite journal |last1=Dantas |first1=Mário A. T. |last2=Campbell |first2=Sean Cody |last3=McDonald |first3=H. Gregory |date=December 2023 |title=Paleoecological inferences about the Late Quaternary giant sloths |url=https://link.springer.com/10.1007/s10914-023-09681-5 |journal=Journal of Mammalian Evolution |language=en |volume=30 |issue=4 |pages=891–905 |doi=10.1007/s10914-023-09681-5 |issn=1064-7554}}</ref> Preserved [[coprolite]]s attributed to ''Megatherium'' suggests that its diet included plants like [[Fabiana (plant)|''Fabiana'']], [[Ephedra (plant)|''Ephedra'']] ''([[Ephedra breana]]''), [[beebrush]], ''[[Junellia]]'', and ''[[Chuquiraga]]''.<ref>H. Gregory McDonald and Gerardo de Iuliis: ''Fossil history of sloths''. In: Sergio F. Vizcaíno and WJ Loughry (eds.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 51–52.</ref>

Whether or not ''Megatherium'' had a slow [[metabolism]] like living tree sloths is uncertain. Analysis of the [[nutrient foramina]] in the [[diaphysis]] (shaft) of the femur of ''Megatherium americanum'' shows that they are more similar to those of other large living mammals like elephants than living tree sloths, which may suggest that it had a metabolism more similar to non-xenarthran mammals and was capable of vigorous activity similar to living elephants.<ref>{{Cite journal |last1=Varela |first1=Luciano |last2=Tambusso |first2=Sebastián |last3=Fariña |first3=Richard |date=2024-08-07 |title=Femora nutrient foramina and aerobic capacity in giant extinct xenarthrans |journal=PeerJ |language=en |volume=12 |pages=e17815 |doi=10.7717/peerj.17815 |issn=2167-8359 |pmc=11316464 |pmid=39131616 |doi-access=free}}</ref> However, isotopic analysis of teeth suggests that ''Megatherium'' had a somewhat lower [[body temperature]] than non-xenarthran mammals, around {{Convert|30-32|C|F}}, comparable to that of living tree sloths, implying a lower metabolic rate.<ref name=":16">{{Cite journal |last=Deak |first=Michael D. |last2=Porter |first2=Warren P. |last3=Mathewson |first3=Paul D. |last4=Lovelace |first4=David M. |last5=Flores |first5=Randon J. |last6=Tripati |first6=Aradhna K. |last7=Eagle |first7=Robert A. |last8=Schwartz |first8=Darin M. |last9=Butcher |first9=Michael T. |date=March 2025 |title=Metabolic skinflint or spendthrift? Insights into ground sloth integument and thermophysiology revealed by biophysical modeling and clumped isotope paleothermometry |url=https://link.springer.com/10.1007/s10914-024-09743-2 |journal=Journal of Mammalian Evolution |language=en |volume=32 |issue=1 |doi=10.1007/s10914-024-09743-2 |issn=1064-7554}}</ref> ''Megatherium americanum'' has been traditionally reconstructed as being covered with a thick coat of fur.<ref name=":16" /> Due to its very large body size, some authors have alternatively argued that ''Megatherium americanum'' was probably hairless like modern elephants for thermodynamic reasons.<ref>Fariña, R. A. (2002). ''Megatherium'', the hairless: appearance of the great Quaternary sloths (Mammalia; Xenarthra). Ameghiniana, 39(2), 241–244.</ref> However this has been disputed, with other authors suggesting based on thermodynamic modelling assuming a living xenarthran-like metabolism that ''Megatherium'' species probably had a dense coat of fur around {{Convert|3|cm|in}} thick to be able to tolerate the relatively cool environments they inhabited.<ref name=":16" />

Based on fossil trackways and the anatomy of its inner ear, which is considerably different from living sloths and more similar to those of armadillos, species of ''Megatherium'', while probably not capable of moving at considerable speed due to limitations of their skeletal anatomy (with one study estimating a max speed of approximately {{Convert|2.2|m/s|ft/s}} or {{Convert|7.92|km/h|mph}}, a fraction of the {{Convert|5-6|m/s|ft/s}} or {{Convert|18-21.6|km/h|mph}} top speed observed for living elephants<ref name=":16" />) were likely significantly more agile and mobile than living sloths, which are only capable of moving {{Convert|0.5-0.6|km/h|mph}}. Species of ''Megatherium'' likely relied on their large adult body size to protect themselves against predators.<ref>{{Cite journal |last1=Billet |first1=G. |last2=Germain |first2=D. |last3=Ruf |first3=I. |last4=de Muizon |first4=C. |last5=Hautier |first5=L. |date=December 2013 |title=The inner ear of Megatherium and the evolution of the vestibular system in sloths |journal=Journal of Anatomy |language=en |volume=223 |issue=6 |pages=557–567 |doi=10.1111/joa.12114 |issn=0021-8782 |pmc=3842198 |pmid=24111879}}</ref> Like many other large mammals, ''Megatherium'' is suggested to have had a slow life cycle in accordance with a [[K-selection]] strategy. ''Megatherium americanum'' is suggested to have given birth to a single large offspring at a time.<ref>{{Cite journal |last=Andrea |first=Elissamburu |date=July 2016 |title=Prediction of offspring in extant and extinct mammals to add light on paleoecology and evolution |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018216300542 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=453 |pages=73–79 |doi=10.1016/j.palaeo.2016.03.033}}</ref>

The anatomy of its forelimb bones suggests that ''M. americanum'' had the ability to rapidly and powerfully extend its arms, which likely made its claws effective stabbing weapons.<ref name=":12" /> It may have used its claws like this to defend itself, as living tree sloths do.<ref name=":11" /> Although some authors in the 19th century suggested that ''Megatherium'' engaged in digging behaviour, this has been disputed by other scholars, and the morphology of its limb bones do not appear to display significant adaptations to digging unlike some ground sloths such as [[Mylodontidae|mylodontids]].<ref>{{Cite journal |last=Amson |first=Eli |last2=Nyakatura |first2=John A. |date=December 2018 |title=The Postcranial Musculoskeletal System of Xenarthrans: Insights from over Two Centuries of Research and Future Directions |url=http://link.springer.com/10.1007/s10914-017-9408-7 |journal=Journal of Mammalian Evolution |language=en |volume=25 |issue=4 |pages=459–484 |doi=10.1007/s10914-017-9408-7 |issn=1064-7554}}</ref>

In the Pampas, ''Megatherium americanum'' lived alongside other megafauna species, including the large ground sloth ''Lestodon'', along with the smaller (but still large) ground sloths ''[[Mylodon]]'', ''[[Glossotherium]],'' and ''[[Scelidotherium]]'', the [[glyptodont]]s (very large armadillos with fused round carapaces covering the body) ''[[Glyptodon]]'', ''[[Doedicurus]]'', and ''[[Panochthus]]'', the large camel-like ungulate ''[[Macrauchenia]]'' and rhinoceros-like ''[[Toxodon]]'', the [[gomphothere]] (elephant-relative) ''[[Notiomastodon]]'', the equines ''[[Hippidion]]'' and ''[[Equus neogeus]]'', the large short-faced bear ''[[Arctotherium]]'', and the large sabertooth cat ''[[Smilodon]].<ref>S.F. Vizcaíno, R.A. Fariña, J.C. Fernicola [http://www.scielo.org.ar/img/revistas/raga/v64n1/html/v64n1a17.htm Young Darwin and the ecology and extinction of Pleistocene South American fossil mammals] Rev. Asoc. Geol. Argent., 64 (1) (2009), pp. 160-169</ref>'' The range of ''Megatherium americanum'' overlaps little with its similarly sized tropical relative ''[[Eremotherium]],'' with their co-occurrence only confidently reported from a few localities in Southern Brazil, and it is unclear whether they were contemporary at these localities.<ref>{{Cite journal |last=Lopes |first=Renato Pereira |last2=Dillenburg |first2=Sergio Rebello |last3=Pereira |first3=Jamil Corrêa |last4=Sial |first4=Alcides Nóbrega |date=2021-09-26 |title=The paleoecology of Pleistocene giant megatheriid sloths: stable isotopes (δ13C, δ18O) of co-occurring Megatherium and Eremotherium from southern Brazil |url=https://sbpbrasil.org/publications/index.php/rbp/article/view/214 |journal=Revista Brasileira de Paleontologia |volume=24 |issue=3 |pages=245–264 |doi=10.4072/rbp.2021.3.06}}</ref>