''Glyptodon'' (; ) is a genus of

glyptodont Glyptodonts are an extinct clade of large, heavily armoured armadillos, reaching up to in height, and maximum body masses of around 2 tonnes. They had short, deep skulls, a fused vertebral column, and a large bony carapace made up of hundreds o ...

, an extinct group of large, herbivorous

armadillo Armadillos () are New World placental mammals in the order (biology), order Cingulata. They form part of the superorder Xenarthra, along with the anteaters and sloths. 21 extant species of armadillo have been described, some of which are dis ...

s, that lived from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 to the early Holocene, around 11,000 years ago, in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. It is one of, if not the, best known genus of glyptodont. ''Glyptodon'' has a long and storied past, being the first named extinct 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 Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. They varied widely in size with the largest, belonging to genera '' Lestodon'', ''Eremotherium'' and ''Megatherium'', being around the size of elephants. ...

Megatherium ''Megatherium'' ( ; from Greek () 'great' + () 'beast') is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Late Pleistocene. It is best known for the elephant-sized type spe ...

'' by early paleontologists. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''G. clavipes'', was described in 1839 by notable British

paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

Sir Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. ...

. Later in the 19th century, dozens of complete skeletons were unearthed from localities and described by paleontologists such as

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino; September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especial ...

and

Hermann Burmeister Karl Hermann Konrad Burmeister (also known as Carlos Germán Conrado Burmeister) (15 January 1807 – 2 May 1892) was a German Argentine zoologist, entomologist, herpetologist, botany, botanist, and coleopterologist. He served as a professor at ...

. During this era, many species of ''Glyptodon'' were dubbed, some of them based on fragmentary or isolated remains. Fossils from North America were also assigned to ''Glyptodon'', but all of them have since been placed in the closely related genus '' Glyptotherium''. It was not until the later end of the 1900s and 21st century that full review of the genus came about, restricting ''Glyptodon'' to just five species under one genus. Glyptodonts were typically large, quadrupedal (four-legged),

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

armadillos with armored

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

s (top shell) that were made of hundreds of interconnected

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amph ...

s (structures in dermis composed of bone). Other pieces of armor covered the tails and

skull roof The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In com ...

s, the skull being tall with

hypsodont Hypsodont is a pattern of dentition characterized by with high crowns, providing extra material for wear and tear. Some examples of animals with hypsodont dentition are cows and horses; all animals that feed on gritty, fibrous material. The oppos ...

(high-crowned) teeth. As for the postcranial anatomy, 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 known. ''Glyptodon'' is morphologically and

phylogenetically In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

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 The term zygoma generally refers to the zygomatic bone, a bone of the human skull that is commonly referred to as the cheekbone or malar bone, but it may also refer to: * The zygomatic arch, a structure in the human skull formed primarily by parts ...

, or cheek bone. Glyptodonts existed for millions of years, though ''Glyptodon'' itself was one of its last surviving members. ''Glyptodon'' was one of many South American

megafauna In zoology, megafauna (from Ancient Greek, Greek μέγας ''megas'' "large" and Neo-Latin ''fauna'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately , this lower en ...

, with many native groups such as notoungulates and ground sloths reaching immense sizes. ''Glyptodon'' had a mixed diet of grasses and other plants, instead living at the edge forests and grasslands where the shrubbery was lower. ''Glyptodon'' had a wide muzzle, an adaptation for bulk feeding. The armor could have protected the animal from predators, of which many coexisted with ''Glyptodon'', including the "saber-tooth cat" ''

Smilodon ''Smilodon'' is an extinct genus of Felidae, felids. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats ...

'', the large

canid Canidae (; from Latin, ''canis'', "dog") is a family (biology), biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamily, subfamilies: the Caninae, a ...

'' Protocyon'', and the giant bear ''

Arctotherium ''Arctotherium'' ("bear beast") is an extinct genus of the Pleistocene Tremarctinae, short-faced bears endemic to Central America, Central and South America. ''Arctotherium'' migrated from North America to South America during the Great American In ...

''. ''Glyptodon'', along with all other glyptodonts, became extinct at the end of the Late Pleistocene, around 12,000 years ago as part of the

Late Pleistocene extinctions The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna, typically defined as animal species having body masses over , which resulted in a collapse in faunal density and diversity acro ...

, along with most large mammals in the Americas. Evidence of hunting of glyptodonts by recently arrived

Paleoindians Paleo-Indians were the first peoples who entered and subsequently inhabited the Americas towards the end of the Late Pleistocene period. The prefix ''paleo-'' comes from . The term ''Paleo-Indians'' applies specifically to the lithic period in ...

suggests that humans may have been a causal factor in the extinctions.

History

Confusion with ''Megatherium''

The history and taxonomy of ''Glyptodon'' is storied and convoluted, as it involved confusion with other genera and 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 (1771–1848) 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 ''

'', a genus of giant

that was named in 1796 by French scientist

Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

(1769–1832). This was the first recorded discovery of a

ine or fossil cingulate. The unusual fossils consisted of a femur,

fragments, and a caudal tube (an armored tail covering found in glyptodontines) that he collected from the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

aged (ca. 2.5-0.011 mya) strata on the banks of the Solís Grande Creek, Uruguay. Larrañaga identified the fossils as those of ''

Dasypus ''Dasypus'' is the only extant genus in the family Dasypodidae. Its species are known as long-nosed or naked-tailed armadillos. They are found in South America, South, Central America, Central, and North America, as well as on the Caribbean islan ...

'' (''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. Larrañaga wrote to French scientist 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''. Larrañaga also noted that similar fossils had been found in "analogous strata near Lake Merrim, on the frontier of the Portuguese colonies (

southern Brazil The South Region of Brazil ( ) is one of the five regions of Brazil. It includes the states of Paraná, Rio Grande do Sul, and Santa Catarina, and covers , being the smallest region of the country, occupying only about 6.76% of the territory of ...

)." These fossils were also likely those of glyptodontines, possibly the closely related '' Hoplophorus''. 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 Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...

n traveler to

Montevideo Montevideo (, ; ) is the capital city, capital and List of cities in Uruguay, largest city of Uruguay. According to the 2023 census, the city proper has a population of 1,302,954 (about 37.2% of the country's total population) in an area of . M ...

, Uruguay named Mr. Sellow, who sent the carapace to

Berlin Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ...

where it was described by Professor von Weiss, who referred it to ''Megatherium''.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. The femur and caudal armor were recovered from the Quegnay in northern Uruguay, while the carapace had been found in the Arapey River. 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.'' 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, and

shoulder girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans, it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists o ...

. 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. 1837 saw the naming of the first glyptodontine, ''Hoplophorus euphractus'', when Danish paleontologist

Peter Wilhelm Lund Peter Wilhelm Lund (14 June 1801 – 25 May 1880) was a Danish Brazilian paleontologist, zoologist, and archeology, archeologist. He spent most of his life working and living in Brazil. He is considered the father of Brazilian paleontology as wel ...

published a series of memoirs on the fossils of Lagoa Santa in Brazil, dating to the Pleistocene. The fossils included osteoderms comparable to those described earlier by Larrañaga, as well as teeth, skull fragments, limb bones, and other elements. After 1837, several new genera and species of glyptodontines were named in quick succession by European paleontologists: ''Chlamydotherium'' based on Sellow's carapace and ''Orycterotherium'' based on Sellow's femur were named by German scientist H. G. Bronn 1838, ''Pachypus'' by Eduard D'Alton in 1839 based on Sellow's 1833 material, ''Neothoracophorus'' (originally ''Thoracophorus'' but the name was preoccupied by a

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

) in 1889 by Argentine paleontologist

Ameghino, F. (1889). ''Contribucion al conocimiento de los mamiferos fosiles de la República Argentina: Obra escrita bajo los auspicios de la Academia nacional de ciencias de la República Argentina para ser presentada á la Exposicion universal de Paris de 1889'' (Vol. 6). PE Coni é hijos. based on isolated osteoderms now identified as those of a juvenile ''Glyptodon'' from Patagonia,Zurita, A. E., Miño-Boilini, Á. R., Soibelzon, E., Carlini, A. A., & Paredes Rios, F. (2009). The diversity of Glyptodontidae (Xenarthra, Cingulata) in the Tarjia Valley (Bolivia): Systematic, biostratigraphic and paleobiogeographic aspects of a particular assemblage.(With 3 figures and 1 table). ''Neues Jahrbuch fur Geologie und Palaontologie-Abhandlungen'', ''251''(2), 225. and ''Lepitherium'' in 1839 by Geoffroy Saint-Hilaire based on Sellow's osteoderms.Saint-Hilaire, E. G. (1831). ''Recherches sur de grands sauriens: trouvés à l'état fossile vers les confins maritimes de la basse normandie, attribués d'abord au crocodile, puis déterminés sous les noms de téléosaurus et sténéosaurus''. Firmin Didot. Saint-Hillaire considered the osteoderms found by Sellow to not even be mammal, but instead of a relative of '' Teleosaurus'', a crocodile-like reptile known from

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

deposits in France.

Richard Owen and referred species

In 1838, British diplomat Sir Woodbine Parish (1796–1882) was sent an isolated molariform attached to a letter about the discovery of several large, Pleistocene-aged fossils from the

Matanza River The Matanza River is a stream in Argentina that originates in the Buenos Aires Province and defines the southern boundary of the Buenos Aires federal district. It empties into the Río de la Plata between Tandanor and Dock Sud. The La Boca neig ...

Buenos Aires Buenos Aires, controlled by the government of the Autonomous City of Buenos Aires, is the Capital city, capital and largest city of Argentina. It is located on the southwest of the Río de la Plata. Buenos Aires is classified as an Alpha− glob ...

, Argentina.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. Parish later collected several more fossils from localities in Las Averias and Villanueva; the latter including a partial skeleton containing a mandible fragment, a set of partial limbs, and a few unguals of a single individual. This skeleton was deposited in Parish's collection at the Royal College of Surgeons in the United Kingdom later that year. Some of these fossils were cast at the

Natural History Museum, London The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum (Lo ...

, but the original fossils were destroyed after German aerial bombing raids hit the college during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

from 1940 to 1941. In 1839, ''Glyptodon'' was named by

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...

(1804–1892) in a chapter of the book ''Buenos Ayres, and the Provinces of the Rio de La Plata: their present state, trade, and debt'' in 1839.Owen, R. (1839). Note on the Glyptodon. ''Buenos Aires and the Provinces of the Rio de La Plata'', 1-178. Within this book, Owen erroneously believed the fossils from Las Averias and Villanueva were all from the same specimen, the name ''Glyptodon'' ("grooved tooth") based on the anatomy of the molariform. A later study found the molariform to actually be from another glyptodontine, '' Panochthus'', and the Villanueva individual was designated the

lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes ...

by Robert Hoffstetter in 1955. However, the lectotype of ''G. clavipes'' undiagnostic and indistinguishable from other ''Glyptodon'' species and even '' Glyptotherium'', making it dubious. The Las Averias individual consists of a, now missing, carapace that was only mentioned in Owen's description, but was used in later reconstructions of the animal. Cuadrelli ''et al'' (2018) designated the species a ''

species inquirenda In biological classification, a ''species inquirenda'' is a species of doubtful identity requiring further investigation. The use of the term in English-language biological literature dates back to at least the early nineteenth century. The ter ...

'' due to this issue and commented that more analyses are necessary. In 1860, Signor Maximo Terrero collected a partial skeleton, including a skull and carapace, of ''G. clavipes'' from the River Salado in southern Buenos Aires and dated to the Pleistocene. These fossils were also sent to the Royal College of Surgeons, where they were described in detail by British paleontologist

Thomas Henry Huxley Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist and anthropologist who specialized in comparative anatomy. He has become known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. The stor ...

(1825–1895) in 1865 during a comprehensive review of the taxon. This skeleton was also destroyed during WWII, but Huxley published several illustrations that presented great amounts of new information on the taxon. 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,'' ''G. tuberculatus'' to ''Panochthus'',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). and ''G. clavicaudatus'' to ''

Doedicurus ''Doedicurus'', from Ancient Greek δοῖδυξ (''doîdux''), meaning "pestle" and oυρά (''ourá''), meaning "tail", is an extinct genus of glyptodont from South America containing one species, ''D. clavicaudatus''. Glyptodonts are a member ...

''. ''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. Other paleontologists also started erecting names for ''Glyptodon'' species after the 1840s, but many of them are now seen as dubious, species inquirenda, or synonymous with previously named species. Par L. Nodot described a new genus and species of glyptodontine in 1857, ''Schistopleurum typus'', on the basis of a caudal tube found in the

Pampas The Pampas (; from Quechua 'plain'), also known as the Pampas Plain, are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all o ...

of Argentina, but it has since been synonymized with ''G. reticulatus''.Nodot, L. (1856). ''Description d'un nouveau genre d'édenté fossile renfermant plusieurs espèces voisines du glyptodon: suivie d'une nouvelle méthode de classification applicable à toute l'histoire naturelle, et spécialement à ces animaux, avec un atlas de douze planches lithographiées; ouvrage publié par l'Academie des sciences, arts et belles-lettres de Dijon et l'atlas avec le concours du Conseil municipal de même ville''. Imprimerie Loireau-Feuchot. Another species now seen as valid, ''G. munizi'', was described in 1881 by Argentine paleontologist Florentino Ameghino (1853–1911) on the basis of several osteoderms found in the Ensenadan of

Arroyo del Medio The Arroyo del Medio ( Spanish, lit. "Middle Creek" or "Middle Stream") is a small river of Argentina, located on (and serving as) the border between the provinces of Buenos Aires and Santa Fe. Its catchment basin comprises about . The Arroyo em ...

, San Nicolás, Argentina. For many years the taxon was only known from the fragmentary holotype, but skull and complete carapace material of the species was later described in detail in 2006 that cemented its validity. German zoologist

described several ''Glyptodon'' fossils in the 1860s, many of them he named as new species of ''Glyptodon'' itself or the synonym ''Schistopleurum'', all of which are now synonyms of ''Glyptodon'' and its species.Burmeister, H. (1866). XXXIX.—On Glyptodon and its allies. ''Annals and Magazine of Natural History'', ''18''(106), 299-304. In 1908, Florentino Ameghino named another species of ''Glyptodon, G. chapalmalensis'', based on a carapace fragment that he had collected from the Atlantic Coast of Buenos Aires Province that dated to the

Chapadmalalan The Chapadmalalan age is a period of geologic time (4.0–3.0 Ma) within the Pliocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Montehermosan and precedes the Uquian age. Fossil content ...

. In 1932, A. Castellanos made a new genus for ''G. chapalmalensis'', ''Paraglyptodon'', which later included another species, ''P. uquiensis'', that was based on more complete specimens that had been collected from Uquía, Argentina between 1909 and 1912. The former species is dubious, but likely not ''Glyptodon'' based on its age. ''P. uquiensis'' has been synonymized with ''Glyptodon'' and is possibly a valid species, though further analysis is necessary to settle its status. Hunterian_Museum_London_1842

Reassessment and ''Glyptotherium''

In the 1950s, Argentine paleontologist Alfredo Castellanos (1893–1975) 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, though its validity is disputed. Castellanos also referred the species ''G. reticulatus'' to the genus, but this unsupported''.'' 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, but it has since been found to be an indeterminate specimen of ''Glyptodon.'' Several ''Glyptodon'' fossils from Pleistocene deposits in Colombia were described in 2012, extending the known range of the genus north greatly. 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 Yamparaez, southeast of the Bolivian city of

Sucre Sucre (; ) is the ''de jure'' capital city of Bolivia, the capital of the Chuquisaca Department and the sixth most populous city in Bolivia. Located in the south-central part of the country, Sucre lies at an elevation of . This relatively high ...

. The strata they were found in was made up of fluvial, sandy sediments that dated to the

Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...

from elevations as high as above sea level. Several additional paratypes were referred to the species from other Late Pleistocene sites in Eastern Cordillera, Bolivia including a nearly complete skull and several osteoderms. 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.'' Reassessment 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.'' 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. Fossils from North America were also described and referred to ''Glyptodon'' starting in 1875, when civil engineers J. N. Cuatáparo and Santiago Ramírez collected a skull, nearly complete carapace, and associated postcranial skeleton of a glyptodontine from a drainage canal near

Tequixquiac Tequixquiac is a municipalities of Mexico, municipality located in the Zumpango Region of the State of Mexico in Mexico. The municipality is located north of Mexico City within the valley that connects the Valley of Mexico with the Mezquital Vall ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

, the fossils coming from the Rancholabrean stage of the Pleistocene. These fossils were the first found of glyptodontines in North America and were named as a new species of ''Glyptodon'', ''G. mexicanum'', but the fossils have since been lost and the species was synonymized with ''Glyptotherium cylindricum''. Several other North American glyptodontine species were named throughout the late 19th-early 20th century, typically based on fragmentary osteoderms. All North American and Central American fossils of glyptodontines have since been referred to the closely related genus ''Glyptotherium'', which was named in 1903 by American paleontologist

Henry Fairfield Osborn Henry Fairfield Osborn, Sr. (August 8, 1857 – November 6, 1935) was an American paleontologist, geologist and eugenics advocate. He was professor of anatomy at Columbia University, president of the American Museum of Natural History for 25 y ...

Taxonomy

''Glyptodon'' is the type genus of Glyptodontinae, an extinct

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

of large, heavily armored armadillos that first evolved in the

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

(ca. 33.5 mya) and went extinct in the Early Holocene during the

(ca. 7,000 years ago). Owen recognized that ''Glyptodon'' was an

edentate Xenarthra (; from Ancient Greek wikt:ξένος, ξένος, xénos, "foreign, alien" + wikt:ἄρθρον, ἄρθρον, árthron, "joint") is a Order (biology), superorder and major clade of Placentalia, placental mammals native to the America ...

, but did not recognize it as being a part of a new subfamily as there were no other recognized glyptodontines in 1839. The family Glyptodontidae was not named until 1869 by

John Edward Gray John Edward Gray (12 February 1800 – 7 March 1875) was a British zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray (1766–1828). The same is used for a z ...

, 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. However, Hermann Burmeister proposed the name Biloricata for the family, believing that glyptodontines possessed a ventral

plastron The turtle shell is a shield for the ventral and dorsal parts of turtles (the Order (biology), order Testudines), completely enclosing all the turtle's vital organs and in some cases even the head. It is constructed of modified bony elements such ...

(bottom shell) and could pull their heads inside their carapaces like turtles. This name lost all use and his theory has not been supported. 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. Glyptodontinae was classified in its own family or even superfamily until in 2016, when

ancient DNA Ancient DNA (aDNA) is DNA isolated from ancient sources (typically Biological specimen, specimens, but also environmental DNA). Due to degradation processes (including Crosslinking of DNA, cross-linking, deamination and DNA fragmentation, fragme ...

was extracted from the carapace of a 12,000 year old ''Doedicurus'' specimen, and a nearly complete

mitochondrial genome Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in ...

was reconstructed (76x coverage). Comparisons with those of modern armadillos revealed that glyptodonts diverged from tolypeutine and chlamyphorine armadillos approximately 34 million years ago in the

late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

. This prompted moving them from their own family, Glyptodontidae, to the subfamily Glyptodontinae within the

extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...

Chlamyphoridae Chlamyphoridae is a family of cingulate mammals. While glyptodonts have traditionally been considered stem-group cingulates outside the group that contains modern armadillos, there had been speculation that the extant family Dasypodidae could ...

. Based on this and the fossil record, glyptodonts would have evolved their characteristic shape and large size (

gigantism Gigantism (, ''gígas'', "wiktionary:giant, giant", plural γίγαντες, ''gígantes''), also known as giantism, is a condition characterized by excessive growth and height significantly above average height, average. In humans, this conditi ...

) quite rapidly, possibly in response to the cooling, drying climate and expansion of open savannas. Chylamyphoridae is a group in the order Cingulata, which includes all extant armadillos in addition to other fossil groups like Pachyarmatheriidae and Pampatheridae. Cingulata is itself within the basal mammal group Xenarthra, which includes an array of American mammal groups like

Vermilingua Anteaters are the four extant mammal species in the suborder Vermilingua (meaning "worm tongue"), commonly known for eating ants and termites. The individual species have other names in English and other languages. Together with sloths, they ar ...

(anteaters) and

Folivora Sloths are a Neotropical realm, Neotropical group of xenarthran mammals constituting the suborder Folivora, including the extant Arboreal locomotion, arboreal tree sloths and extinct terrestrial ground sloths. Noted for their slowness of move ...

(sloths and ground sloths) in the order

Pilosa The Order (biology), order Pilosa is a clade of xenarthran placental mammals, native to the Americas. It includes anteaters and sloths (which include the extinct ground sloths). The name comes from the Latin word for "hairy". Origins and taxon ...

. 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: Richard-owen2

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. Glyptodontinae's tribes were long-considered subfamilies before the 2016 analysis. One tribe, Glyptodontini (typically labeled Glyptodontinae) is a group of younger, larger glyptodontines that evolved in the

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene epoch (geology), epoch made up of two Stage (stratigraphy), stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0. ...

(ca. 13 mya) with '' Boreostemma'', but split into two genera, ''Glyptodon'' in the south and ''Glyptotherium'' in the north, though ''Glyptotherium'' also lived in some areas of South America like Venezuela and eastern Brazil. ''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''. 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. Glyptodontini is often recovered as more basal to most other glyptodontines like ''Doedicurus, Hoplophorus,'' and ''Panochthus.'' Below is the phylogenetic analysis conducted by Cuadrelli ''et al''., 2020 of Glyptodontinae, with Glyptodontidae as a family instead of subfamily, that focuses on advanced glyptodonts:

Description

Like the extant armadillos and all other glyptodontines, ''Glyptodon'' had a large, bony carapace that covered much of its torso, as well as smaller

cephalic A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...

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. In the

axial skeleton The axial skeleton is the core part of the endoskeleton made of the bones of the head and trunk of vertebrates. In the human skeleton, it consists of 80 bones and is composed of the skull (28 bones, including the cranium, mandible and the midd ...

, glyptodontines had strongly fused

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e and pelves completely connected to the carapace, traits convergently evolved in turtles. The large tails of glyptodontines likely served as a counterbalance to the rest of the body and ''Glyptodon'''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''. ''Glyptodon'' had graviportal (weight-bearing), short limbs that are very similar to those in other glyptodontines, being indistinguishable from those of some other taxa. 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. During the Pleistocene, the diversity of glyptodontines diminished but body size increased, with the largest known glyptodont, ''Doedicurus,'' evolving in the Pleistocene. ''Glyptodon'' sizes vary between species and individuals. ''G. clavipes'', the type species, was estimated to weigh , ''G. reticulatus'' weighed a mere to , and ''G. munizi'' weighed . A partial skeleton of ''G. clavipes'' measured with a carapace length of , while the carapaces of other species like ''G. munizi'' and ''G. reticulatus'' measured and long respectively.

Skull, mandible, and dentition

Glyptodont dentition contains entirely

molariforms, which have one of the most extreme examples of hypsodonty known from terrestrial mammals. The dentition is typical of other armadillos, but is fluted on each side by deep grooves. The anterior teeth were compressed, while the posterior teeth were cylindrical. Glyptodont skulls have several unique features; the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

and

palatine A palatine or palatinus (Latin; : ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman Empire, Roman times.

are enlarged vertically to make space for the molariforms, while the braincase is brachycephalic, short and flat. 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. 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

foramina In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, arter ...

. Sutures separating osteoderms are well marked, as in ''Panochthus.'' Other Pleistocene glyptodontines are known by complete/sub-complete skulls, allowing for comparisons to ''Glyptodon''. ''Glyptotherium'''s

are narrow, slender, almost parallel, and close to the

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divi ...

in frontal view; in ''Glyptodon'', this structure is broader, robust, divergent rather than parallel and more laterally placed. The nasal passage was reduced with heavy

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

attachments for some unknown purpose. Some have speculated that the muscle attachments were for a

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

, or trunk, much like that of a

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a Suidae, pig, with a short, prehensile nose trunk (proboscis). Tapirs inhabit jungle and forest regions of South America, South and Centr ...

elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...

. 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

or large snout similar to those in

proboscidea Proboscidea (; , ) is a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Three l ...

ns and

s, but few have accepted this hypothesis. Another suggestion, made by A.E. Zurita and colleagues, is that the large nasal sinuses could be correlated with the cold arid climate of

South America. 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 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

and the palatal plane in ''Glyptodon'' decreases anteriorly, contrary to ''Glyptotherium''; the nasal tip is in a lower plane with respect to the

zygomatic arch In anatomy, the zygomatic arch (colloquially known as the cheek bone), is a part of the skull formed by the zygomatic process of temporal bone, zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the ...

in ''Glyptodon'', but in ''Glyptotherium'' is higher than the zygomatic arch plane. The 1st molariform (molaiform is abbreviated as mf#) of ''Glyptodon'' is distinctly 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. These traits separate the two genera. Within the genus ''Glyptodon'' this trait varies as well, with ''G. reticulatus'' having triloby to a greater degree than ''G. munizi''. Glyptodon_Skelett

The

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

s of ''Glyptotherium'' and ''Glyptodon'' are very similar, but ''Glyptotherium'''s mandible is smaller by about 10% in total size. The angle between the occlusal plane (part of the jaw where upper and lower teeth contact) and the anterior margin of the ascending 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

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

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.

Vertebrae and pelvis

''Glyptodon'' has 7

cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...

, of which the first 3 cervicals were fused together while the rest of the cervicals were free except for the 7th. The 7th cervical and the first 2 dorsal vertebrae were fused together into a trivertebral, a broad, flat bone with very small

spinous processes Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

(projections from a vertebra) and large articular surfaces that held ribs. 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.

Spinous processes Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

in these vertebrae are also heavily reduced, with some being only a thin blade of bone ankylosed with other vertebrae.

Sacral vertebrae The sacrum (: sacra or sacrums), in human anatomy, is a triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity, ...

in ''Glyptodon'' are also fused and 13 in number, which preserve very unusual oval-shaped, thin, and slightly concave ends on the centra. The pelves are also unusual, as they preserve giant ilia and are fused to the rest of the skeleton.

Carapace and osteoderms

''Glyptodon''s osteoderms were attached by 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

conical In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the ''apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines, ...

. The sulci between these raised structures were deep and wide with parallel lines. 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. The osteoderms of the caudal aperture (large 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. The caudal aperture is more vertically oriented in the latter genus, while in ''Glyptotheirum'' it is angled posteriorily. 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. ''Glyptotherium'' however always preserves rosettes. The central and radial

sulci Sulci or Sulki (in Greek , Stephanus of Byzantium, Steph. B., Ptolemy, Ptol.; , Strabo; , Pausanias (geographer), Paus.), was one of the most considerable cities of ancient Sardinia, situated in the southwest corner of the island, on a small isla ...

are deeper and broader in ''Glyptodon'' (ca ) than in ''Glyptotherium'' (ca. ). The osteoderms in ''Glyptodon'' and ''Glyptotherium'' have 5-11 peripheral figures, rugose exposed surfaces, and heights up to . 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. 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.

Tail

''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 In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projectio ...

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. 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. 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%. For example, in specimen MCA 2015 of ''Glyptodon reticulatus'', the terminal tube measured only long in comparison to ''Glyptotherium texanum'' specimen UMMP 34 826's long tube.

Paleobiology

Digging abilities

Many armadillo species have digging capabilities, with large claws adapted for scraping dirt in order to make burrows or forage for food underground. Much of armadillo diets consist of insects and other invertebrates that live underground, in contrast to the herbivorous diets of ''Glyptodon'' and related genera. Being a large armadillo, ''Glyptodon'''s fossorial capabilities have been researched on several occasions. Owen (1841) opposed this idea, though pushback came from Nodot (1856) and Sénéchal (1865) who believed digging was possible for the genus. However, the evolution of a rigid carapace as opposed to a flexible one in extant armadillos as well as a weakly developed 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.

Endocranial anatomy

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 . The

encephalization quotient Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed and predicted brain mass for an animal of a given size, based on nonlinear regre ...

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 The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...

that took up between 4.8 and 9.7% of the entire brain, while around two thirds of it were occupied by the

cerebrum The cerebrum (: cerebra), telencephalon or endbrain is the largest part of the brain, containing the cerebral cortex (of the two cerebral hemispheres) as well as several subcortical structures, including the hippocampus, basal ganglia, and olfac ...

and the rest by the

cerebellum The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or eve ...

. 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 presence of a pronounced sulcus praesylvianus. 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

ankylosaurs Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with Armour (zoology), armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short ...

and

stegosaurs Stegosauria is a group of Herbivore, herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous Period (geology), periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere (North America, Europe a ...

, two types of armored

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

. 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 effect on the skulls of large-headed glyptodontines like ''Glyptodon''.

Feeding and diet

Two main groups of glyptodontines can be distinguished by their feeding habits: narrow-muzzled Miocene propalaehoplophorids and wide-muzzled post-Miocene glyptodontines. The propalaehoplophorids were selective feeders, while the post-Miocene glyptodontines were bulk feeders (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. ''Glyptodon'''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. They had a well-developed snout musculature, along with a mobile neck region that helped them secure food. The hyoid shows a robust design that suggests ''Glyptodon'' had a large and robust tongue, which may have aided in food intake and processing. Like most other xenarthrans, glyptodontines had lower energy requirements than contemporary mammal groups. The stomachs of glyptodontids are mysterious due to being entirely herbivorous, in contrast to modern, omnivorous armadillos which have simple stomachs instead of the chambered ones of sloths. This in conjugation with the proposed idea that aquatic grazing may have caused the isotopes strongly associated with herbivory observed in ''Glyptodon'' fossils. However, aquatic grazing in ''Glyptodon'' is little supported though more backing for this hypothesis has been found in the related ''Glyptotherium''. A carbon isotopic analysis of ''Glyptodon'' bones by França ''et al'' (2015) found that it consumed a variety of both C3 plants and 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. The isotopic conclusion would place ''Glyptodon'' as a mixed browser in most environments, similar to some other glyptodontines. The 2012 paper also noted that ''Glyptodon'' may have had a more flexible diet than previously imagined, with a mix of slightly wooded and slightly open habitats as implied by the consumption of C3 and C4 material. The C4 plants include groups like

Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...

Cyperaceae The Cyperaceae () are a family of graminoid (grass-like), monocotyledonous flowering plants known as wikt:sedge, sedges. The family (biology), family is large; botanists have species description, described some 5,500 known species in about 90 ...

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

, and

Amaranthaceae Amaranthaceae ( ) is a family of flowering plants commonly known as the amaranth family, in reference to its type genus '' Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, maki ...

based on palynological evidence, meaning that ''Glyptodon'' likely ate C4

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s in addition to C3 grasses. 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. The mesowear angles of ''Glyptodon'' were noted to possess a

bimodal distribution In statistics, a multimodal distribution is a probability distribution with more than one mode (i.e., more than one local peak of the distribution). These appear as distinct peaks (local maxima) in the probability density function, as shown ...

, implying a difference between populations, sexes, or species in diet.

Intraspecific combat

Glyptodonts are believed to have taken part in intraspecific fighting. It was presumed that since the tail of ''Glyptodon'' was very flexible and had rings of bony plates, it was used as a weapon in fights. Although its tail could be used for defense against predators, evidence suggests that the tail of ''Glyptodon'' was primarily for attacks on its own kind. A ''G. reticulatus'' fossil displays damage done on the surface of its carapace. A study based on this specimen calculated that ''Glyptodon'' tails would have been able to generate enough force to break the carapace of another ''Glyptodon''. This suggests that they likely fought each other to settle territorial or mating disputes through the use of their tails, much like male-to-male fighting among deer using their antlers.

Ontogeny

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. The skeleton had been collected from the Pleistocene-aged deposits in the 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 glyptodontine and is one of the most complete specimens of an immature ''Glyptodon'' known, though dozens of isolated osteoderms from juveniles are known. The preserved skull measures only 51 mm long, but still bears many characteristics of ''Glyptodon'' such as a subtriangular

naris A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, ...

, a lateral margin on the naris that forms an acute angle of 30-degrees, oval infraorbital foramina, and several other traits. 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.'' In the osteoderms of juvenile ''Glyptodon reticulatus,'' the central figures are larger than the peripheral osteoderms. These central figures are planar, sometimes even concave, and elevated compared to the peripherals. The peripherals in younger individuals are also less distinct and bear weakly marked or absent furrows (grooves that separate osteoderms). On the other hand, peripherals and central figures of adults are similarly sized, distinct, and of similar heights.

Posture

Several interpretations of glyptodontine posture have been made, starting with those by Richard Owen in 1841 using comparative anatomy. Owen theorized that the phalanges were weight-bearing due to their short and broad physiology, in addition to evidence provided in the postcranial skeleton. 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.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. Linear measurements were later taken which provided insight into this hypothesis, finding that

bipedalism Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) Limb (anatomy), limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from ...

would be possible. The patellar articulation with the femur suggests rotation of the lower leg during knee extension and potentially even knee-locking were feasible.

Trackways

The first ever glyptodont footprints were recovered from the late Pleistocene Pehuén-Có fossil site, Argentina, and referred to ''Glyptodon''. Described as the ichnotaxon ''Glyptodontichnus pehuencoensis'' in 2015, the rarity of glyptodont trackways despite their frequency in the fossil record suggests that glyptodonts may have avoided walking on muddy substrates as they'd be especially vulnerable to getting trapped.

Sexual dimorphism and group behavior

No evidence of

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

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. No direct evidence of glyptodontine group behavior has been described, though some localities preserving juveniles, subadults, and adults of ''Glyptotherium'' together are known. Living armadillos are loners and only come together during mating season, with the number of offspring varying between one and even twelve babies depending on the species.

Distribution and paleoecology

''Glyptodon'' is one of the most common Pleistocene glyptodontines with a large range from the lowland

to the towering Andean Mountains of Peru and Bolivia, some fossils found at elevations reaching over above sea level. Only ''G. munizi'' is found in the early-middle Pleistocene, whereas other species are younger. ''G. reticulatus'' is specifically noted to be known from 60ka to as recent as 7ka possibly, though confirmed records only extend to 11 ka. The genus had a generalist diet, which allowed it to fill niches in areas that were inaccessible by grazing genera, with ''G. reticulatus'' representing up to 90% of the glyptodontine fossils in the Tarija Valley of Bolivia. However, in regions such as the Pampas, Mesopotamia, and Uruguay, an array of glyptodontines are known. Further evidence of ''Glyptodon''s adaptability is found in the Pampas, which were semihumid and temperate from 30,000 to 11,000 ka, alternating between the rainy and

dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The t ...

s, over a large area consisting mostly of grasslands dotted with forests and mixed shrubbery. Temperatures in this region were lower than the present, with an estimated mean annual temperature in the Pampas compared to in Buenos Aires today. The Pampas specifically was a mix of semi-arid Patagonian and tropical Brazilian climates during the middle Pleistocene before the expansion of the drier climates. This is in stark contrast to the Bermejo Formation of

Formosa Province Formosa Province () is a province in northeastern Argentina, part of the Gran Chaco Region. Formosa's northeast end touches Asunción, Paraguay, and the province borders the provinces of Chaco and Salta to its south and west, respectively. The ...

, Argentina where the climate and fauna suggest a more arid environment with fewer grasslands. ''G. jatunkhirkhi'' specifically is known only from Andean climate of Eastern Cordillera in Bolivia, causing it to evolve to be smaller in size than lowland species due to less support for larger masses. ''G. jatunkhirkhi'' is not the only example of this in Xenarthra, with species of ''Panochthus'' and ''Pleurolestodon'' evolving to be smaller in size in mountainous regions. SerraGeralI

During the Ensenadan and Marplatan, ''Glyptodon'' coexisted with a variety of mammals unique to the period such as the notoungulate '' Mesotherium'', canid '' Theriodictis,'' and a species of the giant bear ''

''. In areas such as Uruguay, fossils of ''Glyptodon'' have been unearthed alongside the contemporary glyptodontines ''Doedicurus,

Neuryurus ''Neuryurus'' is an extinct genus of glyptodont. It lived from the Late Pliocene to the Early Holocene, and its fossilized remains were discovered in South America. Description This genus, like all glyptodonts, had a heavy armor formed by oste ...

,'' ''Panochthus;'' armadillos '' Chaetophractus, Propaeopus,'' and '' Eutatus;'' and the herbivorous pampathere '' Pampatherium.'' As for their distant relatives the ground sloths, the giant ''Megatherium'' is known, in addition to two species of the scelidothere '' Catonyx'', and the mylodontid genera ''

Mylodon ''Mylodon'' is an extinct genus of ground sloth belonging to the family Mylodontidae, known from southern South America. With a total length of 3 to 4 m and a body mass of 1-2 tonnes, it is one of the largest mylodontids (though it was considerab ...

'' and '' Glossotherium''. Some other groups are known, including the unusual litopterns ''

Macrauchenia ''Macrauchenia'' ("long llama", based on the now-invalid llama genus, ''Auchenia'', from Greek "big neck") is an extinct genus of large ungulate native to South America from the Pliocene or Middle Pleistocene to the end of the Late Pleistocene. I ...

'' and ''

Neolicaphrium ''Neolicaphrium'' is an extinct genus of ungulate mammal belonging to the extinct order Litopterna. This animal lived from the Late Pliocene (Chapadmalalan) to the Late Pleistocene (Lujanian) in southern South America, being the last survivor of ...

,'' notoungulate '' Toxodon'', massive

n ''

Notiomastodon ''Notiomastodon'' is an extinct genus of gomphothere proboscidean (related to modern elephants), endemic to South America from the Pleistocene to the early Holocene. ''Notiomastodon'' specimens reached a size similar to that of the modern Asian ...

'', and the equids '' Equus neogeus'' and ''

Hippidion ''Hippidion'' (meaning ''little horse'') is an extinct genus of equine that lived in South America from the Late Pliocene to the end of the Late Pleistocene (Lujanian), between 2.5 million and 11,000 years ago. They were one of two lineages of eq ...

''. Various

artiodactyls Artiodactyls are placental mammals belonging to the order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other thre ...

have been recorded, including the peccaries ''

Catagonus ''Catagonus'' is a genus of peccaries that contains the living Chacoan peccary, C. wagneri, and several extinct species. The genus has always been restricted to South America. Taxonomy ''Catagonus'' is notable in that the type species, '' C. metr ...

'' and ''Tayassu peccari'', extinct deer '' Morenelaphus'' and '' Antifer'', and two genera of llamas including '' Hemiauchenia'' and ''

Lama Lama () is a title bestowed to a realized practitioner of the Dharma in Tibetan Buddhism. Not all monks are lamas, while nuns and female practitioners can be recognized and entitled as lamas. The Tibetan word ''la-ma'' means "high mother", ...

.'' A variety of carnivorans have been recorded, such as the "saber-toothed" ''

,'' the bear ''Arctotherium bonariense'', and the wolf-like canids '' Protocyon,'' and '' Dusicyon''. Rodents too have been found, such as ''

Holochilus ''Holochilus'' is a genus of semiaquatic rodents in the tribe Oryzomyini of family Cricetidae,* sometimes called marsh rats. It contains five living species, '' H. brasiliensis'', '' H. chacarius'', '' H. nanus'', '' H. oxe'', and '' H. sciureus ...

Hydrochoerus The genus ''Hydrochoerus'' contains two living and three extinct species of rodents from South America, the Caribbean island of Grenada, California and Panama. Capybaras are the largest living rodents in the world. The genus name is derived from ...

'' (capybara), ''

Cavia ''Cavia'' is a genus in the subfamily Caviinae that contains the rodents commonly known as the guinea pigs or cavies. The best-known species in this genus is the domestic guinea pig, ''Cavia porcellus'', a meat animal in South America and a com ...

,'' and '' Microcavia''. Notably, some of the youngest "terror-bird" fossils of the genus '' Psilopterus'' have been unearthed in the area. Material previously assigned to ''Glyptodon'' in northeast Brazil has been reassigned to ''Glyptotherium'', restricting the Brazilian distribution of ''Glyptodon'' to the southern provinces. However, two osteoderms with characteristics similar to those of ''Glyptodon'' have been found in

Sergipe Sergipe (), officially State of Sergipe, is a States of Brazil, state of Brazil. Located in the Northeast Region, Brazil, Northeast Region along the Atlantic Ocean, Atlantic coast of the country, Sergipe is the smallest state in Brazil by geogra ...

state in the northeast, suggesting that both genera occurred in this region during the Pleistocene. ''Glyptodon'''s northernmost locality comes from Pleistocene deposits in central Colombia, though many specimens formerly attributed to the genus come from the bordering country of

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

Predation and relationship with humans

''Glyptodon'' coexisted with a variety of large predators including the cat ''Smilodon,''

jaguar The jaguar (''Panthera onca'') is a large felidae, cat species and the only extant taxon, living member of the genus ''Panthera'' that is native to the Americas. With a body length of up to and a weight of up to , it is the biggest cat spe ...

s'','' and canid ''Protocyon''. This belief is furthered by the discovery of fractured dorsal armor, which implies that ''Glyptodon'' had been in physical conflict with other animals. However, isotope analyses of the

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

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''. 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''.'' 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 The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which land ...

. For this reason, it was hypothesized that the osteoderms developed as a defensive/offensive mechanism to combat the new arrivals of the area. ''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. The ''Glyptotherium'' in question was a juvenile, with a still-developing head shield, making it far more vulnerable to the cat's attack. Although originally theorized by George Brandes to be possible in 1900,Brandes, G. (1900) : Ueber eine Ursache des Aussterbens Diluvialer Säugethiere. Corrblatt d. Deutsch . ''Ges. f. Anthropol. Jahrg. 31. Munichen'' 1901. ''Smilodon'' canines could not pierce the thick carapace osteoderms of glyptodontines.Bohlin, B. (1940). 8. Food habit of the machairodonts, with special regard to ''Smilodon''. Brandes imagined that the evolution of thick glyptodontine armor and long machairodont canines was an example of

coevolution In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well a ...

, but Birger Bohlin argued in 1940 that the teeth were far too fragile to do damage against glyptodontine armor. Glyptodon old drawing

The coexistence of early

hunter-gatherer A hunter-gatherer or forager is a human living in a community, or according to an ancestrally derived Lifestyle, lifestyle, in which most or all food is obtained by foraging, that is, by gathering food from local naturally occurring sources, esp ...

humans and glyptodontines in South America was first hypothesized in 1881 based on fossil discoveries from the Pampas, 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. During this period, a wide array of Xenarthrans inhabited the Pampas were hunted by humans, with evidence demonstrating that the small () glyptodontine ''Neosclerocalyptus,'' the armadillo ''Eutatus'', and the gigantic (2 ton) glyptodontine ''Doedicurus'', the largest glyptodontine known, were hunted. 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. The discoveries there showed the first signs of human hunting on the skulls of glyptodontines. Hunters may have used the shells of dead animals as shelters in inclement weather. ''Glyptodon'' was also a victim of

parasitism Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

, as evidenced by findings of ''Karethraichnus kulindros'' on an articulated carapace of ''G. clavipes'', which are believed to represent traces made by tungid fleas that were related to ''Tunga perforans''.

Extinction

''Glyptodon'', along with all other glyptodonts became extinct around the end of the Late Pleistocene, as part of a wave of extinctions of most large mammals across the Americas. Some evidence suggests that humans drove glyptodontines to extinction. Evidence from the Campo Laborde and La Moderna archaeological sites in the Argentine Pampas suggest that ''Glyptodon'''s relatives ''Doedicurus'' and ''Panochthus'' survived until the Early Holocene, coexisting with humans for a minimum of 4,000 years. This overlap provides support for models showing that the South American Pleistocene extinctions resulted from a combination of climatic change and anthropogenic causes. 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. The extinction rates in South America during the late Pleistocene were the highest out of any continent, with all endemic animals weighing over going extinct by the middle Holocene. 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. The extinction of ''Glyptodon'' notably coincides with the end of the

Antarctic Cold Reversal The Antarctic Cold Reversal (ACR) was a climatic event of intense atmospheric and oceanic cooling across the southern hemisphere (>40°S) between 14,700 and 13,000 years before present ( BP) that interrupted the most recent deglacial climate warm ...

period in which, for 1,700 years, temperatures dropped before spiking after ending at 12.7 ka. 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. 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.

References

{{Taxonbar, from=Q131695 Armadillos Prehistoric cingulates Prehistoric placental genera Pleistocene xenarthrans Pleistocene mammals of South America Pleistocene Argentina Fossils of Argentina Fossils of Bolivia Pleistocene Brazil Fossils of Brazil Pleistocene Paraguay Fossils of Paraguay Pleistocene Peru Fossils of Peru Pleistocene Uruguay Fossils of Uruguay Fossil taxa described in 1839 Taxa named by Richard Owen Pleistocene Colombia Fossils of Colombia