Glyptodon: Difference between revisions

'''''Glyptodon''''' (from [[Greek language{{lit|Greek]] for "grooved or carved tooth":}}; {{etymology|grc|''{{Wikt-lang|grc|γλυπτός}}'' "({{grc-transl|γλυπτός}})|sculptured"||''{{Wikt-lang|grc|ὀδοντ-}}, and{{Wikt-lang|grc|ὀδούς}}'' ({{grc-transl|ὀδοντ-, ὀδούς "}})|tooth"}})<ref>{{cite OED1|glyptodon}}</ref> is a genus of glyptodontine([[glyptodont]], an extinct group of large, herbivorous armadillos) in the family [[Chlamyphoridaearmadillo]] (a family of South American armadillos)s, that lived from the [[Pliocene]], around 3.2 million years ago,<ref name=":0">{{Cite journal |last1=Zurita |first1=Alfredo E. |last2=Carlini |first2=Alfredo A. |last3=Gillette |first3=David |last4=Sánchez |first4=Rodolfo |date=2011-03-01 |title=Late Pliocene Glyptodontinae (Xenarthra, Cingulata, Glyptodontidae) of South and North America: Morphology and paleobiogeographical implications in the GABI |url=https://www.sciencedirect.com/science/article/pii/S0895981111000095 |journal=Journal of South American Earth Sciences |language=en |volume=31 |issue=2 |pages=178–185 |doi=10.1016/j.jsames.2011.02.001 |bibcode=2011JSAES..31..178Z |hdl=11336/41714 |issn=0895-9811}}</ref> to the early Holocene, around 11,000 years ago, in [[Brazil]],South [[Uruguay]], [[Paraguay]], [[Bolivia]], [[Peru]], [[Argentina]], and [[ColombiaAmerica]]. It is one of, if not the, best known genus of glyptodont. ''Glyptodon'' has a long and storied past, being the first named extinct [[Cingulata|cingulate]] and the type genus of the subfamily Glyptodontinae. Fossils of ''Glyptodon'' have been recorded as early as 1814 from Pleistocene aged deposits from Uruguay, though many were incorrectly referred to the [[ground sloth]] ''[[Megatherium]]'' by early paleontologists.

Glyptodonts were typically large, quadrapedralquadrupedal (four-legged), [[Herbivore|herbivorous]] armadillos with armored [[carapace]]s (top shell) that were made of hundreds of interconnected [[osteoderm]]s (structures in dermis composed of bone). Other pieces of armor covered the tails and [[skull roof]]s, the skull being tall with [[hypsodont]] (high-crowned) teeth. As for the postcranial anatomy, [[Pelvis|pelves]] fused to the carapace, an amalgamate vertebral column, short limbs, and small digits are found in glyptodontines. ''Glyptodon'' reached up to 2 meters (6.56 feet) long and 400 kilograms (880 pounds) in weight, making it one of the largest glyptodontines but not as large as its close relative ''Glyptotherium'' or ''[[Doedicurus]],'' the largest known glyptodont. ''Glyptodon'' is morphologically and [[Phylogenetics|phylogenetically]] most similar to ''Glyptotherium,'' however they differ in several ways. ''Glyptodon'' is larger on average, with an elongated carapace, a relatively shorter tail, and a robust [[zygoma]], or cheek bone.

[[File:Georges_Cuvier.jpg|left|thumb|224x224px|[[Georges Cuvier]] (1769-18321769–1832), describer of ''[[Megatherium]]''|alt=Portrait of Georges Cuvier, describer of Megatherium. ]]

The history and taxonomy of ''Glyptodon'' is storied and convoluted, as it involved confusion with other genera and [[Nomen dubium|dubious]] species, as well as a lack of detailed data. The first recorded discovery of ''Glyptodon'' was as early as 1814 when Uruguayan priest, scientist, soldier, and later politician [[Dámaso Antonio Larrañaga]] (1771-18481771–1848) wrote about the discovery of several unusual fossils in his ''Diario de Historia Natural,'' which included his descriptions of many new species of ants, birds, mammals, and even one of the first figures of the extinct ''[[Megatherium]]'', a genus of giant [[ground sloth]] that was named in 1796 by French scientist [[Georges Cuvier]] (1769-18321769–1832).<ref>Cuvier, G. (1796). ''Notice sur le squelette d'une très-grande espèce de quadrupède inconnue jusqu'à présent, trouvé au Paraguay, et déposé au cabinet d'histoire naturelle de Madrid''. de l'imprimerie du Magasin encyclopédique, rue Honoré No 94, vis-à-vis le passage Roch.</ref><ref name="Fariña2013">{{cite book |author1=Fariña, Richard A. |url=https://books.google.com/books?id=kUAKgNfiAvoC&pg=PA184 |title=Megafauna: Giant Beasts of Pleistocene South America |author2=Vizcaíno, Sergio F. |author3=De Iuliis, Gerry |date=22 May 2013 |publisher=Indiana University Press |isbn=978-0-253-00719-3 |oclc=779244424}}</ref> This was the first recorded discovery of a [[glyptodont|glyptodontine]]ine or fossil [[Cingulata|cingulate]].<ref name="Fariña2013" /> The unusual fossils consisted of a femur, [[carapace]] fragments, and a caudal tube (an armored tail covering found in glyptodontines) that he collected from the [[Pleistocene]] aged (ca. 2.5-0.011 mya) strata on the banks of the [[Solís Grande Creek]], Uruguay.<ref name="Fariña2013" /><ref name="Huxley-1865">{{Cite journal |last=Huxley |first=Thomas Henry |date=1865-01-01 |title=II. On the osteology of the genus glyptodon |url=https://royalsocietypublishing.org/doi/abs/10.1098/rstl.1865.0002 |journal=Philosophical Transactions of the Royal Society of London |volume=155 |pages=31–70 |doi=10.1098/rstl.1865.0002|s2cid=111224208 }}</ref> Larrañaga identified the fossils as those of ''[[Dasypus]]'' (''Megatherium''), believing that ''Megatherium'' was a subgenus of ''Dasypus'' based on the incorrect referral of glyptodontine osteoderms to ''Megatherium'' years earlier by Spanish scientist Juan Bautista Bru de Ramón, which misled other scientists to believe that glyptodontine fossils were actually those of armored megatheres.<ref name="Owen-1855">{{Cite journal |last=Owen |first=Professor |date=1855 |title=On the Megatherium (Megatherium Americanum, Cuvier and Blumenbach). Part II.--Vertebrae of the Trunk |url=https://www.jstor.org/stable/108525 |journal=Philosophical Transactions of the Royal Society of London |volume=145 |pages=359–388 |jstor=108525 |issn=0261-0523}}</ref><ref name="Fariña2013" />

Larrañaga wrote to French scientist [[Augustin Saint-Hilaire|Auguste Saint Hilaire]] about the discovery, and the letter was reproduced by Cuvier in 1823 in the second volume of his landmark book ''Recherches sur les ossemens fossiles''.<ref name="Cuvier-1823">{{Cite book |last=Cuvier |first=Georges |url=https://books.google.com/books?id=xqZAAAAAcAAJ&dq=Cuvier,+G.+1824.+Recherches+sur+les+Ossemens+Fossiles,+nouvelle+edition.+G.+Dufour+et+E.+D'Ocagne,+Paris,+547+pp.&pg=PA1 |title=Recherches sur les ossemens fossiles |date=1823 |publisher=chez G. Dufour et E. d'Ocagne |language=fr}}</ref> Larrañaga also noted that similar fossils had been found in "analogous strata near Lake Merrim, on the frontier of the Portuguese colonies ([[South Region, Brazil|southern Brazil]])."<ref name="Cuvier-1823" /><ref name="Owen-1855" /> These fossils were also likely those of glyptodontines, possibly the closely related ''[[Hoplophorus]]''.<ref name="Porpino-2010">{{Cite journal |last1=Porpino |first1=Kleberson de O. |last2=Fernicola |first2=Juan C. |last3=Bergqvist |first3=Lílian P. |date=2010-05-18 |title=Revisiting the intertropical Brazilian species Hoplophorus euphractus (Cingulata, Glyptodontoidea) and the phylogenetic affinities of Hoplophorus |url=https://doi.org/10.1080/02724631003765735 |journal=Journal of Vertebrate Paleontology |volume=30 |issue=3 |pages=911–927 |doi=10.1080/02724631003765735 |bibcode=2010JVPal..30..911P |hdl=11336/69074 |s2cid=83888299 |issn=0272-4634}}</ref> The armored ''Megatherium'' hypothesis was further supported later in 1827 when portions of a ''Glyptodon'' carapace, as well as a partial femur and some caudal armor, were found by a [[Prussia]]n traveler to [[Montevideo]], Uruguay named Mr. Sellow, who sent the carapace to [[Berlin]] where it was described by Professor von Weiss, who referred it to ''Megatherium''.<ref name="Weiss">Weiss, C. S. (1827). ''Über das südliche ende des gebirgszuges von Brasilien in der provinz S. Pedro do Sul und der Banda oriental oder dem staate von Monte Video''. Verlag nicht ermittelbar.</ref> The femur and caudal armor were recovered from the [[Queguay Grande River|Quegnay]] in northern Uruguay, while the carapace had been found in the [[Arapey Grande River|Arapey River]].<ref name="Weiss" /><ref name="Huxley-1865" /> Weiss and other paleontologists noted that the osteoderms closely resembled those of armadillos like ''Dasypus'', but Cuvier's hypothesis was popularized based on the incorrect referral of glyptodontine osteoderms ''Megatherium.''<ref name="Owen-1855" /><ref name="Cuvier-1823" />

Another work on the armored ''Megatherium'' hypothesis was published in 1833 by Berlin scientist E. D'Alton, who described more of the material sent by Sellow, including portions of the limbs, [[Manus (anatomy)|manus]], and [[shoulder girdle]]. D'Alton recognized the great similarities of the fossils to ''Dasypus'' and speculated that it was a giant armadillo, contrary to the notion that they were from ''Megatherium''. Despite this, D'Alton did not erect a new name for the fossils and instead wrote that additional material was necessary to distinguish it from other armadillos. D'Alton did not mention ''Megatherium'' or its osteoderms in the paper, but he implied that all of the "''Megatherium'' armor" was instead from his armadillo. This hypothesis was supported by Laurillard in 1836, who mentioned that a plaster cast of a large armadillo carapace represented a distinct taxon from ''Megatherium'' and that the armor referred to the sloth was instead from an armadillo.<ref name="Huxley-1865" />

In 1838, British diplomat [[Woodbine Parish|Sir Woodbine Parish]] (1796–1882) was sent an isolated [[Molar (tooth)|molariform]] and a letter about the discovery of several large fossils from the [[Matanza River]] in [[Buenos Aires Province|Buenos Aires]], Argentina that dated to the Pleistocene.<ref name="Owen">Owen, R. (1841). VI.—Description of a Tooth and Part of the Skeleton of the Glyptodon clavipes, a large Quadruped of the Edentate Order, to which belongs the Tesselated Bony Armour described and figured by Mr. Clift in the former Volume of the Transactions of the Geological Society; with a consideration of the question whether the Megatherium possessed an analogous Dermal Armour. ''Transactions of the Geological Society of London'', ''6''(1), 81-106.</ref><ref name="Cuadrelli-2018">{{Cite journal |last1=Cuadrelli |first1=Francisco |last2=Zurita |first2=Alfredo E. |last3=Toriño |first3=Pablo |last4=Miño-Boilini |first4=Ángel R. |last5=Rodríguez-Bualó |first5=Santiago |last6=Perea |first6=Daniel |last7=Acuña Suárez |first7=Gabriel E. |date=2018-09-03 |title=Late Pleistocene Glyptodontinae (Mammalia, Xenarthra, Glyptodontidae) from southern South America: a comprehensive review |url=https://doi.org/10.1080/02724634.2018.1525390 |journal=Journal of Vertebrate Paleontology |volume=38 |issue=5 |pages=e1525390 |doi=10.1080/02724634.2018.1525390 |bibcode=2018JVPal..38E5390C |s2cid=92335544 |issn=0272-4634}}</ref> Parish later collected several more fossils from localities in [[Las Averias, Argentina|Las Averias]] and [[Villanueva, Argentina|Villanueva]]; the latter preserved the most complete skeleton which included a mandible fragment, partial limbs, and unguals of a single individual. They were deposited in Parish's collection at the Royal College of Surgeons in the United Kingdom that year. Some of these fossils were cast at the [[Natural History Museum, London]], but the original fossils were destroyed after [[The Blitz|German aerial bombing raids]] hit the college during [[World War II]] from 1940 to 1941.<ref name="Zurita" /><ref name="Cuadrelli-2018" /> ''Glyptodon'' was named by [[Richard Owen]] (1804-18921804–1892), one of the most influential British naturalists of the Victorian Era, writing a chapter about the animal and publishing a reconstruction of its skeleton in the book ''Buenos Ayres, and the provinces of the Rio de La Plata: their present state, trade, and debt'' in 1839.<ref>Parish, W. (1852). ''Buenos Ayres, and the provinces of the Rio de La Plata: their present state, trade, and debt''. Murray.</ref><ref name="Owen-2">Owen, R. (1839). Note on the Glyptodon. ''Buenos Aires and the Provinces of the Rio de La Plata'', 1-178.</ref> Within this book, Owen erroneously believed they were all from the same specimen, the name ''Glyptodon'' ("grooved tooth") based on the anatomy of the molariform.<ref name="Owen-2" /><ref name="Cuadrelli-2018" /> A later study found the molariform to actually be from another glyptodontine, ''[[Panochthus]]'', and the Villanueva individual was designated the [[Type (biology)|lectotype]] by [[Robert Hoffstetter]] in 1955.<ref>Hoffstetter, R. (1955). Sur le genotype de Glyptodon Owen. ''Bulletin du Muséum National d’Historie Naturelle'', ''27''(5), 408-413.</ref> The Las Averias individual consists of a carapace that was only mentioned in Owen's description, but was used in later reconstructions of the animal and has since been lost. An issue with the lectotype of ''G. clavipes'' is that the material is undiagnostic and indistinguishable from other ''Glyptodon'' species and even ''[[Glyptotherium]]'', making it dubious.

Later in 1845, many more fossils found by Parish from Pleistocene layers in Argentina were named as new species of ''Glyptodon'' by Owen: ''G. ornatus, G. reticulatus, G. tuberculatus'', and ''G. clavicaudatus'' in 1847. Of these additional species, only ''G. reticulatus'' is still considered a valid species of ''Glyptodon'' as ''G. ornatus'' was reassigned to the genus ''[[Neosclerocalyptus]],''<ref>Paula Couto, C. D. (1957). Sôbre um gliptodonte do Brasil. ''Boletim Divisão de Geologia e Mineralogia'', ''165'', 1-37.</ref> ''G. tuberculatus'' to ''Panochthus'',<ref name="Burmeister-2">Burmeister, G. (1866). Lista de los mamíferos fósiles del terreno diluviano. In ''Anales del Museo Público de Buenos Aires'' (Vol. 1, No. 3, pp. 121-232).</ref> and ''G. clavicaudatus'' to ''[[Doedicurus]]''.<ref>Burmeister, G. Burmeister 1870–1874. ''Monografia de los glyptodontes en el Museo Público de Buenos Aires. Anales del Museo Público de Buenos Aires'', ''2'', 1-412.</ref> ''G. reticulatus'' was named on the basis of several carapace fragments that had also been recovered from the Matanza River, but they lack detailed locality information and the fossils too were destroyed during WWII. The fragments were cast by the NHMUK as well, being used to diagnose the species.<ref name="Zurita-2018">{{Cite journal |last1=Zurita |first1=Alfredo Eduardo |last2=Gillette |first2=David D. |last3=Cuadrelli |first3=Francisco |last4=Carlini |first4=Alfredo Armando |date=2018-06-01 |title=A tale of two clades: Comparative study of Glyptodon Owen and Glyptotherium Osborn (Xenarthra, Cingulata, Glyptodontidae) |url=https://www.sciencedirect.com/science/article/pii/S0016699517301870 |journal=Geobios |language=en |volume=51 |issue=3 |pages=247–258 |doi=10.1016/j.geobios.2018.04.004 |bibcode=2018Geobi..51..247Z |hdl=11336/83593 |s2cid=134450624 |issn=0016-6995}}</ref>

In the 1950s, Argentine paleontologist [[Alfredo Castellanos]] (1893-19751893–1975) erected new generic names for several species of ''Glyptodon'', the first being ''Glyptocoileus'' and second of these being ''Glyptopedius'' in 1953 that was made for the species ''G. elongatus'' that had been named by Robert Burmeister in 1866 on the basis of a single carapace,<ref name="Burmeister" /> though its validity is disputed.<ref name="Cuadrelli-2020" /><ref name="Cuadrelli-2018" /> Castellanos also referred the species ''G. reticulatus'' to the genus, but this unsupported''.''<ref name="Cuadrelli-2018" /> Yet another genus was erected in 1976 named ''Heteroglyptodon genuarioi'' by F. L. Roselli based on an incomplete skeleton that had been collected from the Pleistocene aged [[Libertad Formation]] in [[Nueva Palmira]], Uruguay,<ref>{{Cite journal |last=Jiménez Zamudio |first=Rafael |date=1988-06-30 |title=Contribución al estudio del plural de la declinación temática latina |url=http://dx.doi.org/10.3989/emerita.1988.v56.i1.612 |journal=Emerita |volume=56 |issue=1 |pages=121–126 |doi=10.3989/emerita.1988.v56.i1.612 |issn=1988-8384}}</ref><ref name="Zurita-2011">{{Cite journal |last1=Zurita |first1=Alfredo Eduardo |last2=Oliveira |first2=Edison Vicente |last3=Toriño |first3=Pablo |last4=Rodriguez-Bualó |first4=Santiago Martín |last5=Scillato-Yané |first5=Gustavo Juan |last6=Luna |first6=Carlos |last7=Krapovickas |first7=Jerónimo |date=2011-01-01 |title=On the taxonomic status of some Glyptodontidae (Mammalia, Xenarthra, Cingulata) from the Pleistocene of South America |url=https://www.sciencedirect.com/science/article/pii/S0753396911000401 |journal=Annales de Paléontologie |language=en |volume=97 |issue=1 |pages=63–83 |doi=10.1016/j.annpal.2011.07.003 |bibcode=2011AnPal..97...63Z |hdl=11336/43130 |issn=0753-3969}}</ref> but it has since been found to be an indeterminate specimen of ''Glyptodon.''<ref name="Zurita-2011" /> Several ''Glyptodon'' fossils from Pleistocene deposits in Colombia were described in 2012, extending the known range of the genus north greatly.<ref name="Zurita-2012">{{Cite journal |last1=Zurita |first1=Alfredo Eduardo |last2=Miño Boilini |first2=Ángel Ramón |last3=Francia |first3=Analia |last4=Arenas Mosqueras |first4=José E. |date=2012 |title=The Pleistocene Glyptodontidae Gray, 1869 (Xenarthra: Cingulata) of Colombia and some considerations about the South American Glyptodontinae |url=https://ri.conicet.gov.ar/handle/11336/30020 |journal=Rev. Bras. Paleontol. |volume=15 |issue=3 |pages=273–280 |doi=10.4072/rbp.2012.3.04 |issn=1519-7530}}</ref>

Another ''Glyptodon'' species was described in 2020 called ''G. jatunkhirkhi'' by several authors led by Argentine zoologist [[Francisco Cuadrelli]] on the basis of an individual preserving a nearly complete carapace, several caudal rings, and a pelvis that had been collected from [[Yamparáez Province|Yamparaez]], {{Convert|24|km|mi}} southeast of the Bolivian city of [[Sucre]]. The strata they were found in was made up of fluvial, sandy sediments that dated to the [[Late Pleistocene]] from elevations as high as {{Convert|4100-2500|m|ft}} above sea level.<ref name="Cuadrelli-2020" /> Several additional paratypes were referred to the species from other Late Pleistocene sites in [[Cordillera Oriental (Bolivia)|Eastern Cordillera]], Bolivia including a nearly complete skull and several osteoderms.<ref name="Cuadrelli-2020" /> In a phylogenetic analysis conducted by Cuadrelli ''et al''., 2020, ''G. jatunkhirki'' was recovered as the most basal ''Glyptodon'' species, despite being the same age as the more derived species ''G. clavipes.'' ReassesmentReassessment of ''Glyptodon'' species began in the late 20th and early 21st centuries, with various hypotheses developing on the number of valid species. Numbers varied, with some authors considering up to 4 species valid, while phylogenetic analyses in 2018 and 2020 only found the species ''G. reticulatus, G. munizi,'' and ''G. jatunkhirkhi'' definitively valid; ''G. clavipes'' and ''G. uquiensis'' as ''species inquirendas.''<ref name="Cuadrelli-2018" /> However a 2016 review of ''G. uquiensis'' determined that ''G. uquiensis'' was actually a juvenile specimen of ''Glyptodon,'' though the species could not be determined.<ref name="Cruz-2016" />

''Glyptodon'' is the type genus of Glyptodontinae, an extinct [[subfamily]] of large, heavily armored armadillos that first evolved in the [[Eocene|Late Eocene]] (ca. 33.5 mya) and went extinct in the [[Greenlandian|Early Holocene]] during the [[Quaternary extinction event|lateLate Pleistocene extinctions]] (ca. 7,000 years ago).<ref name="Cuadrelli-2020" /><ref name="Delsuc20162">{{cite journal |last1=Delsuc |first1=F. |last2=Gibb |first2=G.C. |last3=Kuch |first3=M. |last4=Billet |first4=G. |last5=Hautier |first5=L. |last6=Southon |first6=J. |last7=Rouillard |first7=J.-M. |last8=Fernicola |first8=J.C. |last9=Vizcaíno |first9=S.F. |last10=MacPhee |first10=R.D.E. |last11=Poinar |first11=H.N. |year=2016 |title=The phylogenetic affinities of the extinct glyptodonts |journal=Current Biology |volume=26 |issue=4 |pages=R155–R156 |doi=10.1016/j.cub.2016.01.039 |pmid=26906483 |doi-access=free|bibcode=2016CBio...26.R155D }}</ref> Owen recognized that ''Glyptodon'' was an [[Xenarthra|edentate]], but did not recognize it as being a part of a new subfamily as there were no other recognized glyptodontines in 1839.<ref name="Owen-2" /> The family Glyptodontidae was not named until 1869 by [[John Edward Gray]], who included the genera ''Glyptodon, Panochthus,'' and ''Hoplophorus'' within the group and believed that it was diagnosed by an immovable carapace that was fused to the pelvis.<ref>Gray, J. E. (1869). ''Catalogue of carnivorous, pachydermatous, and edentate Mammalia in the British Museum''. order of the Trustees.</ref> However, Hermann Burmeister proposed the name Biloricata for the family, believing that glyptodontines possessed a ventral [[Turtle shell|plastron]] (bottom shell) and could pull their heads inside their carapaces like turtles. This name lost all use and his theory has not been supported.<ref name="Burmeister" /><ref name="Burmeister-2" /> The internal phylogenetics of Glyptodontidae was analyzed in greater detail by Florentino Ameghino during his descriptions of earlier members of the clade, which proposed that ''Glyptodon'' was descended from earlier genera.<ref name="Ameghino" /><ref name="Soibelzon-2006" />

Glyptodontinae was classified in its own family or even superfamily until in 2016, when [[ancient DNA]] was extracted from the carapace of a 12,000 year old ''Doedicurus'' specimen, and a nearly complete [[mitochondrial genome]] was reconstructed (76x [[Coverage (genetics)|coverage]]). Comparisons with those of modern armadillos revealed that glyptodonts diverged from [[Tolypeutinae|tolypeutine]] and [[Chlamyphorinae|chlamyphorine]] armadillos approximately 34 million years ago in the [[Priabonian|late Eocene]].<ref name="Mitchell2016">{{cite journal |last1=Mitchell |first1=K.J. |last2=Scanferla |first2=A. |last3=Soibelzon |first3=E. |last4=Bonini |first4=R. |last5=Ochoa |first5=J. |last6=Cooper |first6=A. |year=2016 |title=Ancient DNA from the extinct South American giant glyptodont ''Doedicurus'' sp. (Xenarthra: Glyptodontidae) reveals that glyptodonts evolved from Eocene armadillos |url=http://sedici.unlp.edu.ar/handle/10915/101557 |journal=Molecular Ecology |volume=25 |issue=14 |pages=3499–3508 |doi=10.1111/mec.13695 |pmid=27158910|bibcode=2016MolEc..25.3499M |s2cid=3720645 }}</ref><ref name="Delsuc20162" /> This prompted moving them from their own family, Glyptodontidae, to the subfamily Glyptodontinae within the [[Extant taxon|extant]] [[Chlamyphoridae]].<ref name="Delsuc20162" /> Based on this and the fossil record, glyptodonts would have evolved their characteristic shape and large size ([[gigantism]]) quite rapidly, possibly in response to the cooling, drying climate and expansion of open savannas.<ref name="Mitchell2016" /> Chylamyphoridae is a group in the order Cingulata, which includes all extant armadillos in addition to other fossil groups like [[Pachyarmatheriidae]] and [[Pampatheriidae|Pampatheridae]]. Cingulata is itself within the basal mammal group Xenarthra, which includes an array of American mammal groups like [[Anteater|Vermilingua]] (anteaters) and [[Sloth|Folivora]] (sloths and ground sloths) in the order [[Pilosa]]. The following phylogenetic analysis was conducted by Frédéric Delsuc and colleagues in 2016 and represents the phylogeny of Cingulata using ancient DNA from ''Doedicurus'' to determine the position of it and other Glyptodonts:<ref name="Mitchell2016" /><ref name="Delsuc20162" />

[[File:Richard-owen2.jpg|thumb|Portrait of [[Richard Owen|Sir Richard Owen]] (1804-18921804–1892), describer of ''Glyptodon.''|alt=Portrait of Richard Owen.]]

The internal phylogeny of Glyptodontinae is convoluted and in flux, with many species and families erected based on fragmentary or undiagnostic material that lacks comprehensive review.<ref name="Zurita-2011-2" /><ref name="Porpino-2010" /> Glyptodontinae's tribes were long-considered subfamilies before the 2016 analysis.<ref name="Mitchell-2016">{{Cite journal |last1=Mitchell |first1=Kieren J. |last2=Scanferla |first2=Agustin |last3=Soibelzon |first3=Esteban |last4=Bonini |first4=Ricardo |last5=Ochoa |first5=Javier |last6=Cooper |first6=Alan |date=2016 |title=Ancient DNA from the extinct South American giant glyptodont Doedicurus sp. (Xenarthra: Glyptodontidae) reveals that glyptodonts evolved from Eocene armadillos |url=https://onlinelibrary.wiley.com/doi/10.1111/mec.13695 |journal=Molecular Ecology |language=en |volume=25 |issue=14 |pages=3499–3508 |doi=10.1111/mec.13695|pmid=27158910 |bibcode=2016MolEc..25.3499M |s2cid=3720645 }}</ref> One tribe, Glyptodontini (typically labeled Glyptodontinae) is a group of younger, larger glyptodontines that evolved in the [[Middle Miocene]] (ca. 13 mya) with ''[[Boreostemma]]'',<ref>{{Cite journal |last1=Zurita |first1=Alfredo E. |last2=González Ruiz |first2=Laureano R. |last3=Gómez-Cruz |first3=Arley J. |last4=Arenas-Mosquera |first4=Jose E. |date=2013-05-01 |title=The most complete known Neogene Glyptodontidae (Mammalia, Xenarthra, Cingulata) from northern South America: taxonomic, paleobiogeographic, and phylogenetic implications |url=https://doi.org/10.1080/02724634.2013.726677 |journal=Journal of Vertebrate Paleontology |volume=33 |issue=3 |pages=696–708 |doi=10.1080/02724634.2013.726677 |bibcode=2013JVPal..33..696Z |hdl=11336/2971 |s2cid=86099989 |issn=0272-4634}}</ref> but split into two genera, ''Glyptodon'' in the south and ''Glyptotherium'' in the north,<ref name="Zurita-2012" /> though ''Glyptotherium'' also lived in some areas of South America like Venezuela and eastern Brazil.<ref>Oliveira, É. V., Porpino, K. D., & Baretto, A. (2010). On the presence of ''Glyptotherium'' in the Late Pleistocene of Northeastern Brazil, and the status of "''Glyptodon''" and "''Chlamydotherium''". Paleobiogeographic implications. ''Neues Jahrbuch fur Geologie und Palaontologie-Abhandlungen'', ''258''(3), 353.</ref><ref name="Dantas2013" /><ref name="Zurita-2012" /> ''Glyptotherium'' and ''Glyptodon'' lived during the same intervals and are nearly identical to ''Glyptodon'' in many aspects, so much so that the first fossils of ''Glyptotherium'' to be described were misidentified as those of ''Glyptodon''.<ref>Hay, O. P. (1923). ''The Pleistocene of North America and Its Vertebrated Animals from the States East of the Mississippi River and from the Canadian Provinces East of Longitude 95> O'' (No. 22). Carnegie institution of Washington.</ref><ref>Cope, E. D. (1889). the edentata of North America. ''The American Naturalist'', ''23''(272), 657-664.</ref><ref name="Zurita-2018" /> Glyptodontini is distinguishable from other groups for example in that it has large, conical tubercular osteoderms absent or only present on the caudal (tailward) notch on the posterior end of the carapace and different ornamentation of the armor on the carapace than the tail.<ref name="Zurita-2018" /> Glyptodontini is often recovered as more basal to most other glyptodontines like ''Doedicurus, Hoplophorus,'' and ''Panochthus.''<ref>{{Cite journal |last1=Porpino |first1=Kleberson de O. |last2=Fernicola |first2=Juan C. |last3=Cruz |first3=Laura Edith |last4=Bergqvist |first4=Lílian P. |date=2014-07-29 |title=The intertropical Brazilian species of Panochthus (Xenarthra, Cingulata, Glyptodontoidea): a reappraisal of their taxonomy and phylogenetic affinities |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2014.863203 |journal=Journal of Vertebrate Paleontology |language=en |volume=34 |issue=5 |pages=1165–1179 |doi=10.1080/02724634.2014.863203 |bibcode=2014JVPal..34.1165P |hdl=11336/29660 |s2cid=86577502 |issn=0272-4634}}</ref><ref name="Cuadrelli-2020" />

|1=''[[Boreostemma|Boreostemma acostae]]''

|2=''[[Boreostemma|Boreostemma venezolensis]]'' }}

|2=''[[Glyptotherium|Glyptotherium texanum]]'' }}

|2=''[[Doedicurus|Doedicurus clavicaudatus]]'' }}

|2=''[[Panochthus|Panochthus tuberculatus]]''

Like the extant armadillos and all other glyptodontines, ''Glyptodon'' had a large, bony carapace that covered much of its torso, as well as smaller [[Head|cephalic]] armor covering the roof of its head, akin to that in turtles. The carapace was composed of hundreds of small, hexagonal osteoderms (armored structures made of bone), with ''Glyptodon'' carapaces preserving a total of 1,800 osteoderms each. The anatomy of different ''Glyptodon'' species varies greatly, mostly in the species ''G. jatunkhirkhi'' which is more similar to ''Glyptotherium'' in certain aspects.<ref name="Cuadrelli-2020" />

In the [[axial skeleton]], glyptodontines had strongly fused [[vertebra]]e and [[Pelvis|pelves]] completely connected to the carapace, traits convergently evolved in turtles.<ref name="Huxley-1865" /><ref name="Gillette" /> The large tails of glyptodontines likely served as a counterbalance to the rest of the body and ''Glyptodon''<nowiki/>'s caudal armor ended in a blunt tube that was composed of two concentric tubes fused together, in contrast to those of mace-tailed glyptodontines like ''Neosclerocalyptus'' and ''Doedicurus''.<ref name="Gillette" /> ''Glyptodon'' had graviportal (weight-bearing), short limbs that are very similar to those in other glyptodontines, being indistinguishable from those of some other taxa.<ref name="Zurita-2018" /> The digits of ''Glyptotherium'' are very stout and adapted for weight-bearing, though some preserve large claw sheaths that had an intermediate morphology between claws and hooves.<ref name="Gillette" />

During the Pleistocene, the diversity of glyptodontines diminished but body size increased, with the largest known glyptodont, ''Doedicurus,'' evolving in the Pleistocene.<ref name="Carlini-2022">{{Cite journal |last1=Carlini |first1=Alfredo A. |last2=Carrillo-Briceño |first2=Jorge D. |last3=Jaimes |first3=Arturo |last4=Aguilera |first4=Orangel |last5=Zurita |first5=Alfredo E. |last6=Iriarte |first6=José |last7=Sánchez-Villagra |first7=Marcelo R. |date=2022-06-16 |title=Damaged glyptodontid skulls from Late Pleistocene sites of northwestern Venezuela: evidence of hunting by humans? |url=https://doi.org/10.1186/s13358-022-00253-3 |journal=[[Swiss Journal of Palaeontology]] |volume=141 |issue=1 |pages=11 |doi=10.1186/s13358-022-00253-3 |s2cid=249681104 |issn=1664-2384 |doi-access=free |bibcode=2022SwJP..141...11C }}</ref><ref>{{Citation |last=Defler |first=Thomas |title=The Xenarthrans: Armadillos, Glyptodonts, Anteaters, and Sloths |date=2019 |url=https://doi.org/10.1007/978-3-319-98449-0_6 |work=History of Terrestrial Mammals in South America: How South American Mammalian Fauna Changed from the Mesozoic to Recent Times |series=Topics in Geobiology |volume=42 |pages=117–138 |editor-last=Defler |editor-first=Thomas |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-98449-0_6 |isbn=978-3-319-98449-0 |s2cid=92413294 |access-date=2022-07-19}}</ref> ''Glyptodon'' sizes vary between species and individuals. ''G. clavipes'', the type species, was estimated to weigh {{Convert|2,000|kg|lb}},<ref>Fariña, R. A., Vizcaíno, S. F., & Bargo, M. S. (1998). [https://www.researchgate.net/profile/Richard-Farina/publication/257931152_Body_mass_estimation_in_Lujanian_Late_Pleistocene-Early_Holocene_of_South_America_mammal_megafauna/links/0f31752ee23f72a314000000/Body-mass-estimation-in-Lujanian-Late-Pleistocene-Early-Holocene-of-South-America-mammal-megafauna.pdf Body mass estimations in Lujanian (late Pleistocene-early Holocene of South America) mammal megafauna.] ''Mastozoología Neotropical'', ''5''(2), 87-108.</ref><ref name="Delsuc2016">{{cite journal |last1=Delsuc |first1=F. |last2=Gibb |first2=G.C. |last3=Kuch |first3=M. |last4=Billet |first4=G. |last5=Hautier |first5=L. |last6=Southon |first6=J. |last7=Rouillard |first7=J.-M. |last8=Fernicola |first8=J. C. |last9=Vizcaíno |first9=S. F. |last10=MacPhee |first10=R. D.E. |last11=Poinar |first11=H. N. |date=2016-02-22 |title=The phylogenetic affinities of the extinct glyptodonts |url=https://hal.archives-ouvertes.fr/hal-01879335/file/Delsuc_Poinar_CB_Correspondence_Manuscript_with_SuppInfo_rev1.pdf |journal=Current Biology |volume=26 |issue=4 |pages=R155–R156 |doi=10.1016/j.cub.2016.01.039 |pmid=26906483 |doi-access=free|bibcode=2016CBio...26.R155D }}</ref> ''G. reticulatus'' weighed a mere {{Convert|401|kg|lb}} to {{Convert|862|kg|lb}},<ref name="onlinelibrary.wiley.com">{{Cite journal |last1=Vizcaíno |first1=Sergio F. |last2=Blanco |first2=R. Ernesto |last3=Bender |first3=J. Benjamín |last4=Milne |first4=Nick |date=2011 |title=Proportions and function of the limbs of glyptodonts: Glyptodont limbs |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.2010.00228.x |journal=Lethaia |language=en |volume=44 |issue=1 |pages=93–101 |doi=10.1111/j.1502-3931.2010.00228.x|bibcode=2011Letha..44...93V }}</ref> and ''G. munizi'' weighed {{Convert|1,150|kg|lb}}.<ref name="Vizcaíno-2011">{{Cite journal |last1=Vizcaíno |first1=Sergio F. |last2=Cassini |first2=Guillermo H. |last3=Fernicola |first3=Juan C. |last4=Bargo |first4=M. Susana |date=2011 |title=Evaluating Habitats and Feeding Habits Through Ecomorphological Features in Glyptodonts (Mammalia, Xenarthra) |url=https://bioone.org/journals/ameghiniana/volume-48/issue-3/AMGH.v48i3_364_/Evaluating-Habitats-and-Feeding-Habits-Through-Ecomorphological-Features-in-Glyptodonts/10.5710/AMGH.v48i3(364).full |journal=Ameghiniana |volume=48 |issue=3 |pages=305–319 |doi=10.5710/AMGH.v48i3(364) |hdl=11336/69574 |s2cid=85793531 |issn=0002-7014}}</ref> A partial skeleton of ''G. clavipes'' measured {{convert|3.5|m|ft}} with a carapace length of {{Convert|1.7|m|ft}},<ref name="Fariña2013" /><ref name=":1" /> while the carapaces of other species like ''G. munizi'' and ''G. reticulatus'' measured {{Convert|2.2|m|ft}} and {{Convert|2.19|m|ft}} long respectively.<ref name="Zurita-2018" />

Glyptodont dentition contains entirely [[hypsodont]] molariforms, which have one of the most extreme examples of hypsodonty known from terrestrial mammals.{{Sfn|Gillette|Ray|1981|p=200}} TeethThe resembleddentition thoseis typical of another armadilloarmadillos, but wereis fluted on each side by deep grooves. The anterior teeth were compressed, while the posterior teeth were cylindrical.<ref>{{Cite journal |last=Flower |first=W.H. |date=1871 |title=Professor Flower's Hunterian Lectures On The Teeth and Allied Organs In The Mammalia |journal=The British Medical Journal}}</ref> Glyptodont skulls have several unique features; the [[maxilla]] and [[Palate|palatine]] are enlarged vertically to make space for the molariforms, while the braincase is brachycephalic, short and flat.{{Sfn|Gillette|Ray|1981|p=58}} In ''Glyptodon'' and many other glyptodontines, the roof of the skull was covered by a shield composed of polygonal, irregular osteoderms that were variable in size and ankylosed together to form a robust cephalic shield that had a smoothly convex exterior surface without ornamentation.<ref name="Soibelzon-2006" /> Each osteoderm has a rugose and slightly convex dorsal surface, with ornamentation pattern defined by a central figure, slightly elevated and surrounded by an area without peripheral figures or [[Vertebra|foramina]]. Sutures separating osteoderms are well marked, as in ''Panochthus.''<ref name="Soibelzon-2006" /><ref name="Carlini-2008">{{Cite journal |last1=Carlini |first1=Alfredo A. |last2=Zurita |first2=Alfredo E. |last3=Aguilera |first3=Orangel A. |date=2008 |title=North American Glyptodontines (Xenarthra, Mammalia) in the Upper Pleistocene of northern South America |url=https://doi.org/10.1007/BF02988404 |journal=Paläontologische Zeitschrift |language=en |volume=82 |issue=2 |pages=125 |doi=10.1007/BF02988404 |bibcode=2008PalZ...82..125C |s2cid=128528271 |issn=}}</ref> ManyOther skullsPleistocene glyptodontines are known fromby Pleistocenecomplete/sub-complete glyptodontinesskulls, allowing for comparisons to be made with that of ''Glyptodon''.<ref name="Zurita"/><ref name="Zurita-2011-2">{{Cite journal |last1=Zurita |first1=A.E. |last2=Scarano |first2=A.C. |last3=Carlini |first3=A.A. |last4=Scillato-Yané |first4=G.J. |last5=Soibelzon |first5=E. |date=2011-04-04 |title=Neosclerocalyptus spp. (Cingulata: Glyptodontidae: Hoplophorini): cranial morphology and palaeoenvironments along the changing Quaternary |url=https://doi.org/10.1080/00222933.2010.536917 |journal=Journal of Natural History |volume=45 |issue=15–16 |pages=893–914 |doi=10.1080/00222933.2010.536917 |bibcode=2011JNatH..45..893Z |issn=0022-2933 |s2cid=85146482}}</ref> ''Glyptotherium''<nowiki/>'s [[Zygomatic bone|zygoma]] are narrow, slender, almost parallel, and close to the [[sagittal plane]] in frontal view; in ''Glyptodon'', this structure is broader, robust, divergent rather than parallel and more laterally placed.<ref name="Carlini-2022" /><ref name="Zurita-2018" />

The nasal passage was reduced with heavy [[muscle]] attachments for some unknown purpose. Some have speculated that the muscle attachments were for a [[proboscis]], or [[Torso|trunk]], much like that of a [[tapir]] or [[elephant]]. The lower jaws were very deep and helped support massive chewing muscles to help chew coarse fibrous plants. Some paleontologists have proposed that ''Glyptodon'' and some glyptodontines also had a [[proboscis]] or large snout similar to those in [[proboscidea]]ns and [[tapir]]s,{{Sfn|Gillette|Ray|1981|p=202}} but few have accepted this hypothesis.<ref name="Zurita-2011-2" /><ref name="Sergio F. Vizcaíno-2012" /> Another suggestion, made by A.E. Zurita and colleagues, is that the large nasal sinuses could be correlated with the cold arid climate of [[Pleistocene]] South America.<ref name="Sergio F. Vizcaíno-2012">{{cite journal |author1=Fernicola, Juan Carlos |author2=Néstor Toledo |author3=M. Susana Bargo |author4=Sergio F. Vizcaíno |date=October 2012 |title=A neomorphic ossification of the nasal cartilages and the structure of paranasal sinus system of the glyptodont Neosclerocalyptus Paula Couto 1957 (Mammalia, Xenarthra) |journal=Palaeontologia Electronica |volume=15 |issue=3 |pages=1–22 |doi=10.26879/333 |doi-access=free}}</ref><ref>{{cite web |author=Gillette, David D. |date=2010 |title=Glyptodonts in arizonaArizona a saga of supercontinents, sea-floor spreading, savannas, and sabertooth cats |url=http://www.azgs.az.gov/arizona_geology/spring10/article_feature.html |access-date=25 March 2014 |publisher=Arizona Geological Survey |archive-date=29 April 2014 |archive-url=https://web.archive.org/web/20140429180717/http://www.azgs.az.gov/arizona_geology/spring10/article_feature.html |url-status=dead }}</ref> A distinctive bar of bone projects downwards on the cheek, extending over the lower jaw, perhaps providing an anchor for powerful snout muscles. In turn, the [[Infraorbital foramen|infraorbital foramina]] are narrow and not visible in anterior view in ''Glyptotherium'', but in ''Glyptodon'' they are broad and clearly visible in anterior view. In lateral view, the dorso-ventral height between the [[skull roof]] and the [[Palatine bone|palatal plane]] in ''Glyptodon'' decreases anteriorly, contrary to ''Glyptotherium''; the nasal tip is in a lower plane with respect to the [[zygomatic arch]] in ''Glyptodon'', but in ''Glyptotherium'' is higher than the zygomatic arch plane. The 1st molariform (molaiform is abbreviated as mf#) of ''Glyptodon'' is distinctly [[Cusp (anatomy)|trilobate]] (three-lobed) both lingually and labially, nearly as trilobate as the mf2; on the contrary, ''Glyptotherium'' shows a very low trilobation of mf1, which is elliptical in cross-section, the mf2 is weakly trilobate, and the mf3 is trilobate. In both genera, the mf4 to mf8 are fully trilobate and serially identical.<ref name="Zurita-2018" /> These traits separate the two genera.<ref name="Zurita-2018" /> Within the genus ''Glyptodon'' this trait varies as well, with ''G. reticulatus'' having triloby to a greater degree than ''G. munizi''.<ref name="Cuadrelli-2018" />[[File:Glyptodon_Skelett.JPG|thumb|''Glyptodon'' skeleton and shell in [[Museum für Naturkunde]], [[Berlin]]|alt=A Glyptodon skeleton and shell.|228x228px]]The [[Mandible|mandiblesmandible]]s of ''Glyptotherium'' and ''Glyptodon'' are very similar, but ''Glyptotherium''<nowiki/>'s mandible is smaller by about 10% in total size. The angle between the [[Occlusion (dentistry)|occlusal plane]] (part of the jaw where upper and lower teeth contact) and the anterior margin of the ascending [[Ramus mandibulae|ramus]] is approximately 60 in ''Glyptotherium,'' while it is 65° in ''Glyptodon.'' The ventral margin of the horizontal ramus is more concave in ''Glyptodon'' than in ''Glyptotherium''. The [[Mandibular symphysis|symphysis]] area is extended greatly in ''Glyptotherium'' antero-posteriorily compared to ''Glyptodon''. The mf1 is ellipsoidal in ''Glyptotherium'' and the mf2 is "submolariform", while in ''Glyptodon'' both teeth are trilobate.<ref name="Zurita-2018" />

''Glyptodon'' has 7 [[cervical vertebrae]], of which the first 3 cervicals were fused together while the rest of the cervicals were free except for the 7th.<ref name="Huxley-1865" /> The 7th cervical and the first 2 dorsal vertebrae were fused together into a trivertebral, a broad, flat bone with very small [[spinous processes]] (projections from a vertebra) and large articular surfaces that held ribs.<ref name="Huxley-1865" /> All of the other 13 vertebrae in the dorsal column were fused into one long continuous tunnel that is not seen in mammals outside of glyptodontines, some of these vertebrae were so tightly fused that the segments of them cannot be discerned. The centra of these vertebrae were curved, thin bony plates that created a cylinder to support the carapace and the shape of the animal.<ref name="Huxley-1865" /> [[Vertebra|Spinous processes]] in these vertebrae are also heavily reduced, with some being only a thin blade of bone ankylosed with other vertebrae.<ref name="Huxley-1865" /> [[Sacrum|Sacral vertebrae]] in ''Glyptodon'' are also fused and 13 in number, which preserve very unusual oval-shaped, thin, and slightly concave ends on the centra.<ref name="Huxley-1865" /> The pelves are also unusual, as they preserve giant [[Ilium (bone)|ilia]] and are fused to the rest of the skeleton.<ref name="Huxley-1865" />

[[File:Glyptodon asper armor.JPG|left|thumb|Close-up view of carapace|alt=Close-up view of carapace.]][[File:Armour_of_glyptodon.JPG|thumb|''Glyptodon'' carapace in [[Hungarian Natural History Museum]]|alt=A Glyptodon carapace.]]''Glyptodon''{{'}}s osteoderms were attached by [[Synostosis|synotoses]] (bony connections) and were found in double or triple rows on the front and sides of the carapace's edges, as well as in the tail armor and cephalic shield. The carapace's osteoderms were conical with a rounded point, while the ones on the tail were just [[Cone|conical]]. The sulci between these raised structures were deep and wide with parallel lines.<ref name="Zurita2010">{{cite journal |last1=Zurita |first1=A. E. |last2=Soibelzon |first2=L. H. |last3=Soibelzon |first3=E. |last4=Gasparini |first4=G. M. |last5=Cenizo |first5=M. M. |last6=Arzani |first6=H. |year=2010 |title=Accessory protection structures in ''Glyptodon'' Owen (Xenarthra, Cingulata, Glyptodontidae) |journal=Annales de Paléontologie |volume=96 |issue=1 |pages=1–11 |doi=10.1016/j.annpal.2010.01.001 |bibcode=2010AnPal..96....1Z |hdl-access=free |hdl=10915/5356}}</ref> The carapace of ''Glyptodon'' was strongly elongated compared to those of ''Boreostemma'' and ''Glyptotherium,'' with the carapace being relatively 65% longer than the former and 14% than the latter. In ''Glyptodon'', the top-bottom height of the carapace represents 60% of its total length, whereas in ''Glyptotherium'' it is taller at circa 70%. The antero-posterior dorsal profile of the carapace was convex and its posterior half was higher than the anterior. The apex of the carapace was slightly displaced posteriorly in most ''Glyptodon'' species, while in ''Glyptotherium'' and ''Glyptodon jatunkhirkhi'' it was at the center of the midline. The carapace of most species of ''Glyptodon'' is arched subtly, while ''Glyptotherium'' and ''Glyptodon jatunkhirkhi''{{'}}s has a very arched back and convex pre-iliac and concave post-iliac, giving it a saddle-like overhang over the tail. ''Glyptodon'' osteoderms in the antero-lateral regions of the carapace are strongly ankylosed, giving them little flexibility, while in ''Glyptotherium'' they are less ankylosed and more flexible.<ref name="Zurita-2018" /> The osteoderms of the caudal aperture ((argelarge conical osteoderms that protect the base of the tail) are more conical in ''Glyptodon'' and more rounded in ''Glyptotherium'', though in the latter the anatomy of the caudal aperture osteoderms varies by sex while in ''Glyptodon'' it varies by age.<ref name="Zurita-2018" /><ref name="Gillette-2016">{{Cite journal |last1=Gillette |first1=David D. |last2=Carranza-Castañeda |first2=Óscar |last3=White |first3=Richard S. |last4=Morgan |first4=Gary S. |last5=Thrasher |first5=Larry C. |last6=McCord |first6=Robert |last7=McCullough |first7=Gavin |date=2016-06-01 |title=Ontogeny and Sexual Dimorphism of Glyptotherium texanum (Xenarthra, Cingulata) from the Pliocene and Pleistocene (Blancan and Irvingtonian NALMA) of Arizona, New Mexico, and Mexico |url=https://doi.org/10.1007/s10914-015-9309-6 |journal=Journal of Mammalian Evolution |language=en |volume=23 |issue=2 |pages=133–154 |doi=10.1007/s10914-015-9309-6 |s2cid=254699205 |issn=1573-7055}}</ref> The caudal aperture is more vertically oriented in the latter genus, while in ''Glyptotheirum'' it is angled posteriorily.<ref name="Zurita-2018" /> Although frequently used to differentiate the two taxa, ''Glyptodon'' and ''Glyptotherium'' have similar osteoderm morphologies that differ only in several areas. Both genera have tall, thick osteoderms compared to those of many other glyptodontines such as ''Hoplophorus'' and ''Neosclerocalyptus. Glyptodon'' sometimes preserves a "rosette" pattern, where the osteoderm's central figure is surrounded by a row of peripheral figures, while other specimens lack them completely. ''G. reticulatus'' varies from a complete rosette pattern to a reticular surface, which has convex central and peripheral figures.<ref name="Gillette-2016" /><ref name="Zurita-2018" /> ''Glyptotherium'' however always preserves rosettes.<ref name="Gillette-2016" /><ref name="Zurita-2018" /> The central and radial [[Sulcus (anatomy)|sulci]] are deeper and broader in ''Glyptodon'' (ca. 4–6&nbsp;mm) than in ''Glyptotherium'' (ca. 1–2.4&nbsp;mm). The osteoderms in ''Glyptodon'' and ''Glyptotherium'' have 5-11 peripheral figures, rugose exposed surfaces, and heights up to {{Convert|47|mm|in}}.<ref name="Zurita-2018" />

Osteoderms on the ventral side of the body were first mentioned by paleontologist Hermann Burmeister in 1866, postulating that there was a ventral plastron like in turtles based on evidence of small armor in the dermis.<ref name="Burmeister" /> This hypothesis has since been disproven, but in the early 2000s, the presence of osteoderms on ''Glyptodon''{{'}}s face, hind legs, and underside was confirmed in several species. The fossils with these characteristics were from the Pleistocene, evolving in younger species like ''G. reticulatus'' . These small to medium-sized ossicles were actually embedded in the dermis and did not connect in a pattern.<ref name="Zurita2010" />

''Glyptodon'' had very primitive tail anatomy for a glyptodont, possessing eight or nine mobile caudal rings of fused, large, conical osteoderms. These enclosed the base of the tail, which terminated in a short caudal tube composed of two fused caudal rings. Caudal rings were composed of two or three rows of pentagonal osteoderms that transitioned from flat, slightly convex in the posterior rings to conical [[Tubercle|tuberclestubercle]]s by the third caudal ring. The more posterior the rings were, the larger they were, with the exception of the 2nd ring which was the largest and 1st complete ring in the series, creating a cone-shaped tail. The distal scutes are larger, and their free margins are rounded producing a fan-like shape. Most of the osteoderms of the distal row (some individuals preserving up to 12) bear prominent conical outlines, in stark contrast to more advanced glyptodontines like ''Doedicurus'' and ''Panochthus'', which had completely fused tails that formed an inflexible mace or club.<ref>{{Cite journal |last1=Arbour |first1=Victoria M. |last2=Zanno |first2=Lindsay E. |date=2020 |title=Tail Weaponry in Ankylosaurs and Glyptodonts: An Example of a Rare but Strongly Convergent Phenotype |url=https://onlinelibrary.wiley.com/doi/10.1002/ar.24093 |journal=The Anatomical Record |language=en |volume=303 |issue=4 |pages=988–998 |doi=10.1002/ar.24093 |pmid=30835954 |s2cid=73488683 |issn=1932-8486}}</ref> The caudal tube at the distalmost end of the tail is cylinder-shaped with smaller conical osteoderms and is stubbier proportionally in ''Glyptodon''. In ''Glyptotherium'', this caudal tube represents ca. 20% of the total length of the caudal armor, whereas in ''Glyptodon'', this structure represents 13% of the total length.<ref name="Zurita-2018" /> In ''Glyptodon'', the caudal armor length represents circa 30-40% of the carapace's total length in contrast to ''Glyptotherium,'' where this value is greater at around 50%.<ref name="Zurita-2018" /> For example, in specimen MCA 2015 of ''Glyptodon reticulatus'', the terminal tube measured only {{Convert|73.23|mm|in}} long in comparison to ''Glyptotherium texanum'' specimen UMMP 34 826's {{Convert|210|mm|in}} long tube.<ref name="Zurita-2018" />

Many armadillo species have digging capabilities, with large claws adapted for scraping dirt in order to make burrows or forage for food underground.<ref>Vizcaíno, S. F., Fariña, R. A., & Mazzetta, G. V. (1999). Ulnar dimensions and fossoriality in armadillos. ''Acta Theriologica'', ''44''.</ref><ref>Carter, T. S., & Encarnaçao, C. D. (1983). Characteristics and use of burrows by four species of armadillos in Brazil. ''Journal of Mammalogy'', ''64''(1), 103-108.</ref> Much of armadillo diets consist of insects and other invertebrates that live underground,<ref>{{Cite journal |last1=Vizcaíno |first1=Sergio F. |last2=Fariña |first2=Richard A. |date=2007-03-29 |title=Diet and locomotion of the armadillo Peltephilus: a new view |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.1997.tb00446.x |journal=Lethaia |language=en |volume=30 |issue=1 |pages=79–86 |doi=10.1111/j.1502-3931.1997.tb00446.x}}</ref> in contrast to the herbivorous diets of ''Glyptodon'' and related genera.<ref name="Saarinen-2017">{{Cite journal |last1=Saarinen |first1=Juha |last2=Karme |first2=Aleksis |date=2017-06-15 |title=Tooth wear and diets of extant and fossil xenarthrans (Mammalia, Xenarthra) – Applying a new mesowear approach |url=https://www.sciencedirect.com/science/article/pii/S0031018216306630 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=476 |pages=42–54 |doi=10.1016/j.palaeo.2017.03.027 |bibcode=2017PPP...476...42S |issn=0031-0182}}</ref> Being a large armadillo, ''Glyptodon''<nowiki/>'s fossorial capabilities have been researched on several occasions. Owen (1841) opposed this idea,<ref name="Owen" /> though pushback came from Nodot (1856) and Sénéchal (1865) who believed digging was possible for the genus.<ref name="Nodot" /><ref name="Sénéchal" /> However, the evolution of a rigid carapace as opposed to a flexible one in extant armadillos as well as a weakly developed [[Humerus|deltoid crest]] on the humerus (upper arm bone) provided evidence against fossorial hypotheses. The elbow had a great range of movement, as with digging cingulates, but this is more likely to be due to size adaptations.<ref>{{Cite journal |last1name=Vizcaíno |first1=Sergio F. |last2=Blanco |first2=R. Ernesto |last3=Bender |first3=J. Benjamín |last4=Milne |first4=Nick |date=2011 |title=Proportions and function of the limbs of glyptodonts: Glyptodont limbs |url=https://"onlinelibrary.wiley.com"/doi/10.1111/j.1502-3931.2010.00228.x |journal=Lethaia |language=en |volume=44 |issue=1 |pages=93–101 |doi=10.1111/j.1502-3931.2010.00228.x}}</ref><ref>{{Cite journal |last1=Amson |first1=Eli |last2=Nyakatura |first2=John A. |date=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 |s2cid=254693335 |issn=1064-7554}}</ref>

[[File:Glyptodontidae brains - Gervais 1869.png|alt=Endocasts of Glyptodon and Doedicurus |left|thumb|[[Endocast|Endocasts]]s of ''Glyptodon'' (left) and ''Doedicurus'' (right).|256x256px]]

Several complete skulls of ''Glyptodon'' enable the endocranial anatomy to be analyzed, as well as compared to other well-preserved taxa like ''Doedicurus'' and ''Panochthus''. The brain cavities of the larger glyptodontines ''Glyptodon, Doedicurus,'' and ''Panochthus'' had a braincase volume of {{Convert|213 to 234|cm3|U.S.oz}}. The [[encephalization quotient]] of these taxa are 0.12 to 0.4, lower than most modern armadillos (0.44-1.06) and corresponds to those of pampatheres. The brain of the glyptodontines had an extensive [[olfactory bulb]] that took up between 4.8 and 9.7% of the entire brain, while around two thirds of it were occupied by the [[cerebrum]] and the rest by the [[cerebellum]]. Overall, this is akin to that of other armadillos, but in the latter the cerebrum is smaller relative to the cerebellum and the braincase's total volume. Deviating from the armadillos with their wide olfactory bulb, glyptodontines and pampatheres have elongated and triangular olfactory systems. Several other neuroanatomical characteristics differ between glyptodontines and armadillos, such as the prescencepresence of a pronounced [[Sulcus (neuroanatomy)|sulcus praesylvianus]].<ref name=":2">{{Cite journal |last1=Tambusso |first1=P Sebastián |last2=Fariña |first2=Richard A. |date=2015-09-03 |title=Digital cranial endocast of Pseudoplohophorus absolutus (Xenarthra, Cingulata) and its systematic and evolutionary implications |url=http://www.tandfonline.com/doi/full/10.1080/02724634.2015.967853 |journal=Journal of Vertebrate Paleontology |language=en |volume=35 |issue=5 |pages=e967853 |doi=10.1080/02724634.2015.967853 |bibcode=2015JVPal..35E7853T |s2cid=86537473 |issn=0272-4634}}</ref><ref name=":3">{{Cite journal |last1=Sebastián Tambusso |first1=P. |last2=Fariña |first2=Richard A. |date=2015 |title=Digital endocranial cast of Pampatherium humboldtii (Xenarthra, Cingulata) from the Late Pleistocene of Uruguay |url=https://sjpp.springeropen.com/articles/10.1007/s13358-015-0070-5 |journal=[[Swiss Journal of Palaeontology]] |language=en |volume=134 |issue=1 |pages=109–116 |doi=10.1007/s13358-015-0070-5 |bibcode=2015SwJP..134..109S |s2cid=86652394 |issn=1664-2384}}</ref>

In general, living cingulates have smaller brains than anteaters and sloths for reasons unknown. Several theories have been made as to why, such as a shorter rearing phase of offspring, dedication of resources to the development of the carapace, and other biological and functional handicaps. Members of Cingulata also tend to have extremely low metabolisms, causing less energy flow to the development of the brain's neurons. The pattern of large bodies bearing adequate protection and a reduction of intelligence is found in several other groups such as [[Ankylosauria|ankylosaurs]] and [[Stegosauria|stegosaurs]], two types of armored [[dinosaur]]. However, the carapace itself is considered as a restrictive functional component as it prohibited much neck movement and forced a reduced brain size. This reduction thus resulted in weight loss in the skull, which had a great affecteffect on the skulls of large-headed glyptodontines like ''Glyptodon''.<ref name=":2" /><ref name=":3" />

Two main groups of glyptodontines can be distinguished by their feeding habits: narrow-muzzled Miocene propalaehoplophorids and wide-muzzled post-Miocene glyptodontines.<ref>{{Cite web |title=Bargo M. S. Vizcaíno S. F. — Paleobiology of Pleistocene ground sloths (Xenarthra, Tardigrada) : biomechanics, morphogeometry and ecomorphology applied to the masticatory apparatus. Ameghiniana |url=https://www.researchgate.net/publication/262718932 |access-date=2015-10-30 |website=ResearchGate}}</ref> The propalaehoplophorids were selective feeders, while the post-Miocene glyptodontines were [[bulk feedersfeeder]]s (obtain nutrients by consuming an entire plant). However, because of their body form and fusion of the cervical vertebrae glyptodontines would have needed to forage near the ground. Their craniomandibular joint limited their jaw to side-to-side movement.<ref name="Fariña-2001">{{Cite journal |last=Fariña |first=R.A. |date=2001 |title=Carved Teeth and Strange Jaws: How Glyptodonts Masticated. |url=https://www.app.pan.pl/archive/published/app46/app46-219.pdf |journal=Acta Palaeontologica Polonica}}</ref> ''Glyptodon''<nowiki/>'s jaws had large ridges of osteodentine which could effectively be used to grind food particles before shearing and pushing them via the constant motion of the mandible.<ref name="Fariña-2001" /> They had a well-developed snout musculature, along with a mobile neck region that helped them secure food.<ref name="Gillette1981">{{Cite journal |last=Gillette |first=R. |date=21 December 1981 |title=Glyptodonts of North America |url=http://www.sil.si.edu/smithsoniancontributions/Paleobiology/pdf_lo/SCtP-0040.pdf |journal=Smithsonian Publications |access-date=2015-10-29}}</ref> The hyoid shows a robust design that suggests ''Glyptodon'' had a large and robust tongue, which may have aided in food intake and processing.<ref>{{Cite journal |last1=Pérez |first1=Leandro M. |last2=Toledo |first2=Néstor |last3=De Iuliis |first3=Gerardo |last4=Bargo |first4=M. Susana |last5=Vizcaíno |first5=Sergio F. |date=2010 |title=Morphology and function of the hyoid apparatus of fossil xenarthrans (mammalia) |url=https://onlinelibrary.wiley.com/doi/10.1002/jmor.10859 |journal=Journal of Morphology |language=en |volume=271 |issue=9 |pages=1119–1133 |doi=10.1002/jmor.10859|pmid=20730924 |s2cid=8106788 }}</ref><ref>Zamorano, M., Scillato-Yané, G. J., Soibelzon, E., Soibelzon, L. H., Bonini, R., & Rodriguez, S. (2018). [https://www.researchgate.net/profile/Martin-Zamorano-2/publication/324703634_Hyoid_apparatus_of_Panochthus_sp_Xenarthra_Glyptodontidae_from_the_Late_Pleistocene_of_the_Pampean_Region_Argentina_Comparative_description_and_muscle_reconstruction/links/5ade1b23aca272fdaf88f295/Hyoid-apparatus-of-Panochthus-sp-Xenarthra-Glyptodontidae-from-the-Late-Pleistocene-of-the-Pampean-Region-Argentina-Comparative-description-and-muscle-reconstruction.pdf Hyoid apparatus of Panochthus sp.(Xenarthra; Glyptodontidae) from the Late Pleistocene of the Pampean region (Argentina). Comparative description and muscle reconstruction.] ''Neues Jahrbuch für Geologie und Paläontologie Abhandlungen'', ''288'', 205-219.</ref>

Like most other xenarthrans, glyptodontines had lower energy requirements than contemporary mammal groups.<ref>{{Cite journal |last1=Vizcaíno |first1=Sergio F. |last2=Cassini |first2=Guillermo H. |last3=Fernicola |first3=Juan C. |last4=Bargo |first4=M. Susana |year=2011 |title=Evaluating Habitats and Feeding Habits Through Ecomorphological Features in Glyptodonts (Mammalia, Xenarthra) |url=https://www.researchgate.net/publication/257931077 |journal=Ameghiniana |pages=305–319 |doi=10.5710/AMGH.v48i3(364) |hdl=11336/69574 |access-date=2015-10-29 |s2cid=85793531}}</ref> The stomachs of glyptodontids are mysterious, asdue modernto armadillos arebeing entirely herbivorous, in contrast to modern, omnivorous andarmadillos which have simple stomachs instead of the chambered ones of sloths.<ref name="Bocherens-2017">{{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=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> This in conjugation with the proposed idea that aquatic grazing may have caused the isotopes strongly associated with herbivory observed in ''Glyptodon'' fossils.<ref name="Bocherens-2017" /> However, aquatic grazing in ''Glyptodon'' is little supported<ref>Fariña, R.A., 1995. Limb bone strength and habits in large glyptodonts. ''Lethaia'', 28: 189-196.</ref> though more backing for this hypothesis has been found in the related ''Glyptotherium''.<ref>{{Cite journal |last1=Lessa |first1=Carlos Micael Bonfim |last2=Gomes |first2=Verônica Santos |last3=Cherkinsky |first3=Alexander |last4=Dantas |first4=Mário André Trindade |date=2021-12-01 |title=Isotopic paleoecology (δ13C, δ18O) of two megamammals assemblages from the late pleistocene of Brazilian intertropical region |url=https://www.sciencedirect.com/science/article/pii/S0895981121004223 |journal=Journal of South American Earth Sciences |language=en |volume=112 |pages=103576 |doi=10.1016/j.jsames.2021.103576 |bibcode=2021JSAES.11203576L |s2cid=244181217 |issn=0895-9811}}</ref><ref>{{Cite journal |last1=Omena |first1=Érica Cavalcante |last2=Silva |first2=Jorge Luiz Lopes da |last3=Sial |first3=Alcides Nóbrega |last4=Cherkinsky |first4=Alexander |last5=Dantas |first5=Mário André Trindade |date=2021-10-03 |title=Late Pleistocene meso-megaherbivores from Brazilian Intertropical Region: isotopic diet ( δ 13 C), niche differentiation, guilds and paleoenvironmental reconstruction ( δ 13 C, δ 18 O) |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1789977 |journal=Historical Biology |language=en |volume=33 |issue=10 |pages=2299–2304 |doi=10.1080/08912963.2020.1789977 |bibcode=2021HBio...33.2299O |s2cid=225543776 |issn=0891-2963}}</ref><ref name="Gillette" /> A carbon isotopic analysis of ''Glyptodon'' bones by França ''et al'' (2015) found that it consumed a variety of both [[C3 carbon fixation|C3]] plants and [[C4 carbon fixation|C4]] grasses at lower latitudes while it ate exclusively C3 grasses at higher ones, implying an ecological shift based on the climate. A 2012 analysis of isotopes supports this, but the isotopic results are not backed by morphological evidence.<ref name="Fariña-2001" /> The isotopic conclusion would place ''Glyptodon'' as a mixed browser in most environments, similar to some other glyptodontines.<ref name="França-2015">{{Cite journal |last1=França |first1=Lucas de Melo |last2=de Asevedo |first2=Lidiane |last3=Dantas |first3=Mário André Trindade |last4=Bocchiglieri |first4=Adriana |last5=Avilla |first5=Leonardo dos Santos |last6=Lopes |first6=Renato Pereira |last7=da Silva |first7=Jorge Luíz Lopes |date=2015-01-01 |title=Review of feeding ecology data of Late Pleistocene mammalian herbivores from South America and discussions on niche differentiation |url=https://www.sciencedirect.com/science/article/pii/S0012825214001858 |journal=Earth-Science Reviews |language=en |volume=140 |pages=158–165 |doi=10.1016/j.earscirev.2014.10.006 |bibcode=2015ESRv..140..158F |issn=0012-8252}}</ref><ref name="Domingo-2012">{{Cite journal |last1=Domingo |first1=Laura |last2=Prado |first2=José Luis |last3=Alberdi |first3=María Teresa |date=2012-11-08 |title=The effect of paleoecology and paleobiogeography on stable isotopes of Quaternary mammals from South America |url=https://www.sciencedirect.com/science/article/pii/S0277379112003307 |journal=Quaternary Science Reviews |language=en |volume=55 |pages=103–113 |doi=10.1016/j.quascirev.2012.08.017 |bibcode=2012QSRv...55..103D |issn=0277-3791}}</ref> The 2012 paper also noted that ''Glyptodon'' may have had a more flexible diet than previously imagined,<ref>Pomi, L. H. (2008). [http://www.scielo.org.ar/scielo.php?pid=S0002-70142008000200019&script=sci_arttext&tlng=pt Una nueva asociación de vertebrados fósiles de Edad Ensenadense (Plioceno tardío-Pleistoceno medio) de la provincia de Buenos Aires, Argentina.] ''Ameghiniana'', ''45''(2), 503-510.</ref> with a mix of slightly wooded and slightly open habitats as implied by the consumption of C3 and C4 material.<ref name="Domingo-2012" /><ref name="Vizcaíno-2011" /> The C4 plants include groups like [[Poaceae]], [[Cyperaceae]], [[Asteraceae]], and [[Amaranthaceae]] based on palynological evidence, meaning that ''Glyptodon'' likely ate C4 [[Floweringflowering plant|flowering plants]]s in addition to C3 grasses.<ref>{{Cite journal |last=Sage |first=Rowan F. |date=2004 |title=The evolution of C 4 photosynthesis |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2004.00974.x |journal=New Phytologist |language=en |volume=161 |issue=2 |pages=341–370 |doi=10.1111/j.1469-8137.2004.00974.x |pmid=33873498 |issn=0028-646X}}</ref><ref name="França-2015" /> A mesowear analysis supported their conclusion, however, finding that mixed-feeding causing blunt wear that suggests a more abrasion-dominated diet. This is similar to that of ''Neosclerocalyptus'', but in contrast to ''Hoplophorus'' which had sharper wear ends. ''Neosclerocalyptus'' favored more open environments despite this, as found by isotopic studies.<ref name="Zurita-2011-2" /><ref name="Vizcaíno-2011" /> The mesowear angles of ''Glyptodon'' were noted to possess a [[Multimodal distribution|bimodal distribution]], implying a difference between populations, sexes, or species in diet.<ref name="Saarinen-2017" />

In 2009, a partial skeleton of a prenatal individual of ''Glyptodon'' was described that had been found inside of the pelvic region of a carapace of an adult.<ref name="Zurita-2009">{{Cite journal |last1=Zurita |first1=Alfredo Eduardo |last2=Miño-Boilini |first2=Angel R. |last3=Soibelzon |first3=Esteban |last4=Scillato-Yané |first4=Gustavo J. |last5=Gasparini |first5=Germán M. |last6=Paredes-Ríos |first6=Freddy |date=2009-09-01 |title=First record and description of an exceptional unborn specimen of Cingulata Glyptodontidae: Glyptodon Owen (Xenarthra) |url=https://www.sciencedirect.com/science/article/pii/S1631068309000694 |journal=Comptes Rendus Palevol |language=en |volume=8 |issue=6 |pages=573–578 |doi=10.1016/j.crpv.2009.04.003 |bibcode=2009CRPal...8..573Z |hdl=11336/37710 |issn=1631-0683}}</ref> The skeleton had been collected from the Pleistocene-aged deposits in the [[Tarija|Tarija Valley]] of Bolivia and included a partial skull, partial mandible, and fragments from the scapulae and femora. The skeleton is the only known prenatal specimen of a glyptodontineandglyptodontine and is one of the most complete specimens of an immature ''Glyptodon'' known, though dozens of isolated osteoderms from juveniles are known.<ref name="Zurita-2009" /> The preserved skull measures only 51&nbsp;mm long, but still bears many characteristics of ''Glyptodon'' such as a subtriangular [[Nostril|naris]], a lateral margin on the naris that forms an acute angle of 30-degrees, oval infraorbital foramina, and several other traits.<ref name="Zurita-2009" /> However, the mandible differs in that the ascending ramus is at a 90-degree angle in contrast to the 60-70 degree angles preserved in adults. Interestingly, this mandibular morphology is alike to that in some specimens of ''Glyptotherium cylindricum.''<ref name="Carlini-2008" /><ref name="Zurita-2009" />

Several interpretations of glyptodontinepostureglyptodontine posture have been made,<ref>{{Cite journal |last1=Amson |first1=Eli |last2=Nyakatura |first2=John A. |date=2018-12-01 |title=The Postcranial Musculoskeletal System of Xenarthrans: Insights from over Two Centuries of Research and Future Directions |url=https://doi.org/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 |s2cid=254693335 |issn=1573-7055}}</ref> starting with those by Richard Owen in 1841 using comparative anatomy.<ref name="Owen" /> Owen theorized that the phalanges were weight-bearing due to their short and broad physiology, in addition to evidence provided in the postcranial skeleton.<ref name="Owen" /> It was also proposed that an upright posture was possible for ''Glyptodon,'' first by Sénéchal (1865) who stated that the tail could be an equilibrium for the front half of the body as well as a method of supporting the legs.<ref name="Sénéchal">Sénéchal, D. L. (1865). ''Notice sur l'armure ou le dermato-squelette et le système dentaire du Glyptodon clavipes, et particularités biologiques de cet animal, déduites d'après l'étude de ses restes fossiles''. Balitout, Questroy et Cie.</ref> Linear measurements were later taken which provided insight into this hypothesis, finding that [[bipedalism]] would be possible.<ref>Fari a, R. A., & Vizcaíno, S. F. (1997). Allometry of the bones of living and extinct armadillos (Xenarthra, Dasypoda). ''Zeitschrift fur Saugetierkunde'', ''62'', 65-70.</ref><ref>{{Cite journal |last1=Fariña |first1=Richard A. |last2=Vizcaı́no |first2=Sergio F. |last3=Blanco |first3=R. Ernesto |date=1997-04-21 |title=Scaling of the Indicator of Athletic Capability in Fossil and Extant Land Tetrapods |url=https://www.sciencedirect.com/science/article/pii/S0022519396903239 |journal=Journal of Theoretical Biology |language=en |volume=185 |issue=4 |pages=441–446 |doi=10.1006/jtbi.1996.0323 |bibcode=1997JThBi.185..441F |issn=0022-5193}}</ref> The [[Patella|patellar articulation]] with the femur suggests rotation of the lower leg during knee extension and potentially even knee-locking were feasible.<ref>Shockey, B. J. (2001). Specialized knee joints in some extinct, endemic, South American herbivores. ''Acta Palaeontologica Polonica'', ''46''(2).</ref>

No evidence of [[sexual dimorphism]] in ''Glyptodon'' has been described, but it has been observed in the close relative ''Glyptotherium'' based on fossils found in Pliocene deposits in Arizona''.'' In the genus, the caudal aperture of males and females differ in that the marginal osteoderms of males are much more conical and convex than those of females. Even in the carapaces of newborn ''Glyptotherium'', the marginal osteoderms are either conical or flat, which enables their sex to be determined.<ref name="Gillette-2016" /> No direct evidence of glyptodontinegroupglyptodontine group behavior has been described, though some localities preserving juveniles, subadults, and adults of ''Glyptotherium'' together are known.<ref name="Gillette-2016" /><ref name="Carlini-2022" /> Living armadillos are loners and only come together during mating season, with the number of offspring varying between one toand even twelve babies depending on the species.<ref>Superina, M. (2000). ''Biologie und Haltung von Gürteltieren (Dasypodidae)'' (Doctoral dissertation, Uitgever niet vastgesteld).</ref>

''Glyptodon'' coexisted with a variety of large predators including the cat ''Smilodon,'' [[jaguar]]s'','' and canid ''Protocyon''.<ref name="Bocherens-2016">{{Cite journal |last1=Bocherens |first1=Hervé |last2=Cotte |first2=Martin |last3=Bonini |first3=Ricardo |last4=Scian |first4=Daniel |last5=Straccia |first5=Pablo |last6=Soibelzon |first6=Leopoldo |last7=Prevosti |first7=Francisco J. |date=2016-05-01 |title=Paleobiology of sabretooth cat Smilodon populator in the Pampean Region (Buenos Aires Province, Argentina) around the Last Glacial Maximum: Insights from carbon and nitrogen stable isotopes in bone collagen |url=https://www.sciencedirect.com/science/article/pii/S0031018216000912 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=449 |pages=463–474 |doi=10.1016/j.palaeo.2016.02.017 |bibcode=2016PPP...449..463B |hdl=11336/43965 |issn=0031-0182}}</ref><ref>Montalvo, C. I., Zárate, M. A., Bargo, M. S., & Mehl, A. (2013). [https://www.researchgate.net/profile/M-Susana-Bargo/publication/259484888_Registro_Faunistico_y_Paleoambientes_del_Cuaternario_Tardio_Provincia_de_la_Pampa_Argentina/links/5433d9210cf2bf1f1f264a74/Registro-Faunistico-y-Paleoambientes-del-Cuaternario-Tardio-Provincia-de-la-Pampa-Argentina.pdf Registro faunístico y paleoambientes del Cuaternario tardío, provincia de La Pampa, Argentina.] ''Ameghiniana'', ''50''(6), 554-570.</ref> This belief is furthered by the discovery of fractured dorsal armor, which implies that ''Glyptodon'' had been in physical conflict with other animals.<ref name="Zurita2010" /> However, [[Isotope analysis|isotope analyses]] of the [[collagen]] from ''Glyptodon'' and other mammals of the Pampas region by Bocherens ''et al''. (2015) discovered little evidence to support the idea of predators feeding on ''Glyptodon''.<ref name="Bocherens-2016" /> Instead, it was found that ''Glyptodon'' as well as herbivorous mammals living in denser forests made up a smaller portion of carnivore diets, whereas open grazers such as ''Lestodon'' and ''Macrauchenia'' were consumed more often''.''<ref name="Bocherens-2016" /> Furthermore, the appearance of secondary armor in the dermis of ''Glyptodon'' coincides with the arrival of North American predators in South America during the [[Great American Interchange]].<ref name=":0" /> For this reason, it was hypothesized that the osteoderms developed as a defensive/offensive mechanism to combat the new arrivals of the area.<ref name="Zurita2010" />

''Smilodon'' may have occasionally preyed upon glyptodontines, based on a skull of ''Glyptotherium texanum'' which bears the distinctive elliptical puncture marks that best match those of the [[machairodont]] cat, indicating that the predator successfully bit into the skull through the armored cephalic shield.<ref>{{cite book |last=Antón |first=Mauricio |title=Sabertooth |date=2013 |publisher=University of Indiana Press |isbn=978-0-253-01042-1 |location=Bloomington, Indiana |pages=203–204}}</ref> The ''Glyptotherium'' in question was a juvenile, with a still-developing head shield, making it far more vulnerable to the cat's attack.<ref name="Gillette2">{{cite journal |last=Gillette |first=D. D. |date=Spring 2010 |title=Glyptodonts in Arizona |url=http://azgeology.azgs.arizona.edu/archived_issues/azgs.az.gov/arizona_geology/spring10/article_feature.html |journal=Arizona Geology |publisher=[[Arizona Geological Survey]] |access-date=2018-08-17}}</ref> Although originally theorized by George Brandes to be possible in 1900,<ref name=":25">Brandes, G. (1900) : Ueber eine Ursache des Aussterbens Diluvialer Säugethiere. Corrblatt d. Deutsch . ''Ges. f. Anthropol. Jahrg. 31. Munichen'' 1901.</ref> ''Smilodon'' canines could not pierce the thick carapace osteoderms of glyptodontines.<ref name=":26">Bohlin, B. (1940). 8. Food habit of the machairodonts, with special regard to ''Smilodon''.</ref> Brandes imagined that the evolution of thick glyptodontinearmorglyptodontine armor and long machairodont canines was an example of [[coevolution]],<ref name=":25" /> but Birger Bohlin argued in 1940 that the teeth were far too fragile to do damage against glyptodontinearmorglyptodontine armor.<ref name=":26" /><ref name="Zurita2010" /> [[File:Glyptodon old drawing.jpg|thumb|Humans hunting ''Glyptodon'', by [[Heinrich Harder]]|alt=Humans hunting Glyptodon.|236x236px]]

The coexistence of early [[hunter-gatherer]] humans and glyptodontines in South America was first hypothesized in 1881 based on fossil discoveries from the Pampas,<ref>Vogt, C. (1881). Squelette humain associe aux glyptodontidae. Bulletin de la Societe d’Antropologie de Paris, 3(4), 693–699</ref> and many fossil discoveries from the Late Pleistocene to Early Holocene have been unearthed since that exhibit human predation on glyptodontines. No fossils of ''Glyptodon'' preserving direct interactions have been unearthed, but it did inhabit this region alongside humans. At the site of Pay Paso 1, an archaeological site in northwestern Uruguay preserving human-made spear points and other signs of culture were found associated with fossils of ''Glyptodon'' and the horse ''Equus.'' These were used for radiocarbon dating using collagen, supposedly dating to around 9,000 to 9,500 BP but these dates cannot be verified.<ref>{{Cite journal |last=Suárez |first=Rafael |date=2015 |title=The Paleoamerican Occupation of the Plains of Uruguay: Technology, Adaptations, and Mobility |url=http://www.tandfonline.com/doi/full/10.1179/2055556314Z.00000000010 |journal=PaleoAmerica |language=en |volume=1 |issue=1 |pages=88–104 |doi=10.1179/2055556314Z.00000000010 |s2cid=128985617 |issn=2055-5563}}</ref><ref name="Zurita-2018" /> During this period, a wide array of Xenarthrans inhabited the Pampas were hunted by humans, with evidence demonstrating that the small ({{convert|300|–|450|kg|abbr=on|disp=comma}}) glyptodontine ''Neosclerocalyptus,''<ref name="Quiñones">{{Cite journal |last1=Quiñones |first1=Sofía I. |last2=De los Reyes |first2=Martin |last3=Zurita |first3=Alfredo E. |last4=Cuadrelli |first4=Francisco |last5=Miño-Boilini |first5=Ángel R. |last6=Poiré |first6=Daniel G. |date=2020-11-01 |title=Neosclerocalyptus Paula Couto (Xenarthra, Glyptodontidae) in the late Pliocene-earliest Pleistocene of the Pampean region (Argentina): Its contribution to the understanding of evolutionary history of Pleistocene glyptodonts |url=https://www.sciencedirect.com/science/article/pii/S0895981120302443 |journal=Journal of South American Earth Sciences |language=en |volume=103 |pages=102701 |bibcode=2020JSAES.10302701Q |doi=10.1016/j.jsames.2020.102701 |issn=0895-9811 |s2cid=225024450}}</ref> the armadillo ''Eutatus'', and the gigantic (2 ton) glyptodontine ''Doedicurus'', the largest glyptodontineknownglyptodontine known, were hunted.<ref>{{Cite journal |last1=Politis |first1=Gustavo G. |last2=Messineo |first2=Pablo G. |last3=Stafford |first3=Thomas W. |last4=Lindsey |first4=Emily L. |date=2019 |title=Campo Laborde: A Late Pleistocene giant ground sloth kill and butchering site in the Pampas |journal=Science Advances |language=en |volume=5 |issue=3 |pages=eaau4546 |bibcode=2019SciA....5.4546P |doi=10.1126/sciadv.aau4546 |issn=2375-2548 |pmc=6402857 |pmid=30854426}}</ref> The only other records of human predation from outside the Pampas area a partial carapace, which was eviscerated by humans, and several skulls preserving signs that they were dispatched by human tools. All were found in Venezuela.<ref>{{Cite journal |last1=Bryan |first1=Alan L. |last2=Casamiquela |first2=Rodolfo M. |last3=Cruxent |first3=José M. |last4=Gruhn |first4=Ruth |last5=Ochsenius |first5=Claudio |date=1978-06-16 |title=An El Jobo Mastodon Kill at Taima-taima, Venezuela |url=https://www.science.org/doi/10.1126/science.200.4347.1275 |journal=Science |language=en |volume=200 |issue=4347 |pages=1275–1277 |doi=10.1126/science.200.4347.1275 |pmid=17738722 |bibcode=1978Sci...200.1275B |s2cid=42568763 |issn=0036-8075}}</ref><ref name="Carlini-2022" /> The discoveries there showed the first signs of human hunting on the skulls of glyptodontines.<ref>{{Cite journal |last1name=Prates":5" |first1=Luciano |last2=Perez |first2=S. Ivan |date=2021-04-12 |title=Late Pleistocene South American megafaunal extinctions associated with rise of Fishtail points and human population |journal=Nature Communications |language=en |volume=12 |issue=1 |pages=2175 |bibcode=2021NatCo..12.2175P |doi=10.1038/s41467-021-22506-4 |issn=2041-1723 |pmc=8041891 |pmid=33846353}}</ref> Hunters may have used the shells of dead animals as shelters in inclement weather.<ref>Fidalgo, F., ''et al.'' (1986) "Investigaciones arqueológicas en el sitio 2 de Arroyo Seco (Pdo. de Tres Arroyos, prov. de Buenos Aires, República Argentina)" In: Bryan, Alan (ed.) (1986) ''New evidence for the Pleistocene peopling of the Americas'' Peopling of the Americas Symposia Series, Center for the Study of Early Man, University of Maine, Orono, Maine, {{ISBN|0-912933-03-8}}, pp. 221–269, in Spanish</ref><ref>Politis, Gustavo G. and Gutierrez, Maria A. (1998) "Gliptodontes y Cazadores-Recolectores de la Region Pampeana (Argentina)" ("''Glyptodonts and Hunter-Gatherers in the Pampas Region (Argentina)''") ''Latin American Antiquity''9(2): pp.111–134 in Spanish</ref>

}}</ref> Evidence from the Campo Laborde and La Moderna archaeological sites in the Argentine Pampas suggest that ''Glyptodon'<nowiki/>''s relatives ''Doedicurus'' and ''Panochthus'' survived until the Early Holocene, coexisting with humans for a minimum of 4,000 years.<ref name="Politis2008">{{cite journal|last1=Politis|first1=G. G.|last2=Messineo|first2=P. G.|title=The Campo Laborde site: New evidence for the Holocene survival of Pleistocene megafauna in the Argentine Pampas|journal=Quaternary International|volume=191|issue=1|date= November 2008 |pages=98–114 |doi=10.1016/j.quaint.2007.12.003|bibcode=2008QuInt.191...98P }}</ref> This overlap provides support for models showing that the South American Pleistocene extinctions resulted from a combination of climatic change and anthropogenic causes.<ref name="Politis2008" /> These sites have been interpreted as ones used for butchering megafauna (''Megatherium'' and ''Doedicurus''); however, some of the chronology has been problematic and controversial, due to poor preservation of the collagen used for dating.<ref name="Politis2008" /> The extinction rates in South America during the Quaternarylate Extinction EventPleistocene were the highest out of any continent, with all endemic animals weighing over {{Convert|100 |kg|lb}} going extinct by the middle Holocene.<ref name="Fariña2013" /> This supports the idea of human hunting as a drive for the extinction of ''Glyptodon,'' as the arrival of humans around 16,000 years BP to such a formerly isolated continent may have caused extinction rates to become higher.<ref name=":5">{{Cite journal |last1=Prates |first1=Luciano |last2=Perez |first2=S. Ivan |date=2021-04-12 |title=Late Pleistocene South American megafaunal extinctions associated with rise of Fishtail points and human population |journal=Nature Communications |language=en |volume=12 |issue=1 |pages=2175 |doi=10.1038/s41467-021-22506-4 |issn=2041-1723 |pmc=8041891 |pmid=33846353|bibcode=2021NatCo..12.2175P }}</ref><ref name="Fariña2013" /><ref>{{Cite journal |last1=Prates |first1=Luciano |last2=Politis |first2=Gustavo G. |last3=Perez |first3=S. Ivan |date=2020-07-22 |title=Rapid radiation of humans in South America after the last glacial maximum: A radiocarbon-based study |journal=PLOS ONE |language=en |volume=15 |issue=7 |pages=e0236023 |doi=10.1371/journal.pone.0236023 |issn=1932-6203 |pmc=7375534 |pmid=32697794 |bibcode=2020PLoSO..1536023P |doi-access=free }}</ref>

The extinction of ''Glyptodon'' notably coincides with the end of the [[Antarctic Cold Reversal]] period in which, for 1,700 years, temperatures dropped before spiking after ending at 12.7 ka.<ref>{{Cite journal |last1=Orombelli |first1=Giuseppe |last2=Maggi |first2=Valter |last3=Delmonte |first3=Barbara |date=2010-06-01 |title=Quaternary stratigraphy and ice cores |url=https://www.sciencedirect.com/science/article/pii/S1040618209003474 |journal=Quaternary International |series=Plio-Pleistocene Correlation and Global Change |language=en |volume=219 |issue=1 |pages=55–65 |doi=10.1016/j.quaint.2009.09.029 |bibcode=2010QuInt.219...55O |issn=1040-6182}}</ref><ref>{{Cite journal |last1=Weber |first1=M. E. |last2=Clark |first2=P. U. |last3=Kuhn |first3=G. |last4=Timmermann |first4=A. |last5=Sprenk |first5=D. |last6=Gladstone |first6=R. |last7=Zhang |first7=X. |last8=Lohmann |first8=G. |last9=Menviel |first9=L. |last10=Chikamoto |first10=M. O. |last11=Friedrich |first11=T. |last12=Ohlwein |first12=C. |date=2014 |title=Millennial-scale variability in Antarctic ice-sheet discharge during the last deglaciation |url=https://www.nature.com/articles/nature13397 |journal=Nature |language=en |volume=510 |issue=7503 |pages=134–138 |doi=10.1038/nature13397 |pmid=24870232 |bibcode=2014Natur.510..134W |s2cid=205238911 |issn=1476-4687}}</ref> Many climatic fluctuations occurred during the late Pleistocene between humid and dry cycles, with ''Glyptodon'' preferring drier climates. Following the Antarctic Cold Reversal, temperatures rose and the climate became more consistently humid, which then led C3 grasses to become increasingly replaced by C4 grasses and southern beech trees. These changes led vulnerable, grazing-specialized forms like glyptodontines, toxodonts, and some ground sloths to become extinct.<ref>{{Cite journal |last1=Villavicencio |first1=Natalia A. |last2=Werdelin |first2=Lars |date=2018-09-01 |title=The Casa del Diablo cave (Puno, Peru) and the late Pleistocene demise of megafauna in the Andean Altiplano |url=https://www.sciencedirect.com/science/article/pii/S0277379118301318 |journal=Quaternary Science Reviews |language=en |volume=195 |pages=21–31 |doi=10.1016/j.quascirev.2018.07.013 |bibcode=2018QSRv..195...21V |s2cid=134626837 |issn=0277-3791}}</ref><ref>{{Cite journal |last1=Hubbe |first1=Alex |last2=Hubbe |first2=Mark |last3=Karmann |first3=Ivo |last4=Cruz |first4=Francisco W. |last5=Neves |first5=Walter A. |date=2011 |title=Insights into Holocene megafauna survival and extinction in southeastern Brazil from new AMS 14C dates |url=https://www.cambridge.org/core/journals/quaternary-research/article/abs/insights-into-holocene-megafauna-survival-and-extinction-in-southeastern-brazil-from-new-ams-14c-dates/38AB0ACF3EE6A9405937A0E22A613F8F |journal=Quaternary Research |language=en |volume=79 |issue=2 |pages=152–157 |doi=10.1016/j.yqres.2012.11.009 |s2cid=129827927 |issn=0033-5894}}</ref> Around 11.5 ka, temperatures peaked before again dropping, resulting in the extinction of several different genera of mammals including some megafauna. ''Glyptodon'' along with genera such as ''Glossotherium'' and ''Morenelaphus'' were wiped out, though several other groups lived for several thousand years after.<ref name="Mitchell-2016" /><ref name="Ubilla-2018" />