Glyptodon
Glyptodon is a genus of glyptodont, an extinct group of large, herbivorous armadillos that lived from the Pliocene, around 3.2 million years ago, to the early Holocene, around 11,000 years ago, in South America. 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 Megatherium by early paleontologists.
The type species, G. clavipes, was described in 1839 by notable British paleontologist Sir Richard Owen. Later in the 19th century, dozens of complete skeletons were unearthed from localities and described by paleontologists such as Florentino Ameghino and Hermann Burmeister. 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, herbivorous armadillos with armored carapaces that were made of hundreds of interconnected osteoderms. Other pieces of armor covered the tails and skull roofs, the skull being tall with hypsodont 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 long and 400 kilograms in weight, making it one of the largest glyptodontines known. Glyptodon is morphologically and 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.
Glyptodonts existed for millions of years, though Glyptodon itself was one of its last surviving members. Glyptodon was one of many South American megafauna, 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, the large canid Protocyon, and the giant bear Arctotherium.
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, along with most large mammals in the Americas. Evidence of hunting of glyptodonts by recently arrived Paleoindians 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 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. This was the first recorded discovery of a glyptodontine or fossil cingulate. The unusual fossils consisted of a femur, carapace fragments, and a caudal tube that he collected from the Pleistocene aged strata on the banks of the Solís Grande Creek, Uruguay. Larrañaga identified the fossils as those of Dasypus , 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 an extract from the letter was reproduced by Cuvier in 1823 in the eighth volume of his landmark book Recherches sur les ossemens fossiles. Larrañaga also noted that similar fossils had been found in "analogous strata near Lake Mirrim, on the frontier of the Portuguese colonies". 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 Friedrich Sellow, a Prussian traveler to Montevideo, Uruguay, who sent the carapace to Berlin where it was described by Christian Samuel Weiss, who referred it to Megatherium. The femur and caudal armor were recovered from the Queguay 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, but Cuvier's hypothesis was popularized based on the incorrect referral of glyptodontine osteoderms to Megatherium.
Another work on the armored Megatherium hypothesis was published in 1833 by the German scientist Eduard Joseph d'Alton, who described more of the material sent by Sellow, including portions of the limbs, 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 Charles Léopold 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 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 and Orycterotherium were named by German scientist Heinrich Georg Bronn in 1838, Pachypus by Eduard D'Alton in 1839, and Lepitherium in 1839 by Geoffroy Saint-Hilaire based on Sellow's osteoderms. Saint-Hilaire 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 deposits in France.
Richard Owen and referred species
In 1838, British diplomat Sir Woodbine Parish was sent an isolated molariform attached to a letter about the discovery of several large, Pleistocene-aged fossils from the Matanza River in Buenos Aires, Argentina. Parish later collected several more fossils from localities in Las Averias and Villanueva; the latter including a partial skeleton containing a mandible fragment and a set of partial limbs. This skeleton was deposited in Parish's collection at the Royal College of Surgeons upon his return to the United Kingdom. Some of these fossils were cast at the Natural History Museum, London, but the original fossils were destroyed after German aerial bombing raids hit the college during World War II from 1940 to 1941. In 1839, Glyptodon was named by Richard Owen 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. Within this book, Owen erroneously believed the fossils from Las Averias and Villanueva were all from the same specimen, which he named Glyptodon 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 by Robert Hoffstetter in 1955. However, the lectotype of G. clavipes was 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 designated the species a species inquirenda 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 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, and G. clavicaudatus to Doedicurus. 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 of Argentina, but it has since been synonymized with G. reticulatus. Another species now seen as valid, G. munizi, was described in 1881 by Argentine paleontologist Florentino Ameghino on the basis of several osteoderms found in the Ensenadan of Arroyo del Medio, 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 Hermann Burmeister 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. 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. 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.File:Hunterian_Museum_London_1842.png|thumb|The Hunterian Museum at the Royal College of Surgeons with a mounted skeleton of Glyptodon'' in the bottom right|alt=Illustration of the Hunterian Museum featuring a mounted skeleton of Glyptodon.|304x304px