Glyptodont in the context of "Cingulata"

Glyptodon (lit. 'grooved or carved tooth'; from Ancient Greek γλυπτός (gluptós) 'sculptured' and ὀδοντ-, ὀδούς (odont-, odoús) 'tooth') 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.

Xenarthra (/zɛˈnɑːrθrə/; from Ancient Greek ξένος (xénos), meaning "strange, foreign", and ἄρθρον (árthron), meaning "joint") is a superorder and major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Extinct xenarthrans include the glyptodonts, pampatheres and ground sloths, with some glyptodonts and ground sloths reaching sizes of several tonnes, much larger than any living xenarthran. Xenarthrans originated in South America during the late Paleocene about 60 million years ago. They evolved and diversified extensively in South America during the continent's long period of isolation in the early to mid Cenozoic Era. They spread to the Antilles by the early Miocene and, starting about 3 million years ago, spread to Central and North America as part of the Great American Interchange. Nearly all of the formerly abundant megafaunal xenarthrans became extinct at the end of the Pleistocene as part of the end-Pleistocene extinction event.

Glyptotherium (from Ancient Greek for 'grooved or carved beast') is a genus of glyptodont (an extinct group of large, herbivorous armadillos) in the family Chlamyphoridae that lived from the Early Pliocene, about 3.9 million years ago, to the Late Pleistocene, around 15,000 years ago. It was widely distributed, living in the United States, Mexico, Guatemala, Costa Rica, Honduras, El Salvador, Panama, Venezuela, Colombia, and Brazil. Fossils that had been found in the Pliocene Blancan Beds in Llano Estacado, Texas were named Glyptotherium texanum by American paleontologist Henry Fairfield Osborn in 1903. Another species, G. cylindricum, was named in 1912 by fossil hunter Barnum Brown on the basis of a partial skeleton that had been unearthed from the Pleistocene deposits in Jalisco, Mexico. The two species differ in several aspects, including age: G. texanum is from the older Early Pliocene to Early Pleistocene strata, whereas G. cylindricum is exclusive to the Late Pleistocene.

Glyptotherium was a large, four-legged (quadrupedal), herbivorous armadillo with an armored top shell (carapace) that was made of hundreds of interconnected osteoderms (structures in dermis composed of bone). Other pieces of armor covered the tail and cranium roof, while small pebbly pieces of armor were in the skin. Glyptotherium grew up to 2 meters (6.56 feet) in length and 400 kilograms (880 pounds), making it one of the largest glyptodonts known. Glyptotherium is morphologically most similar to Glyptodon: though they differ in several ways. Glyptotherium is smaller on average, with a shorter carapace, a longer tail, and had a different distribution.

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 amphibians), various groups of dinosaurs (most notably ankylosaurs and stegosaurians), phytosaurs, aetosaurs, placodonts, and hupehsuchians (marine reptiles with possible ichthyosaur affinities).

Osteoderms are uncommon in mammals, although they have occurred in many xenarthrans (armadillos and the extinct glyptodonts and mylodontid ground sloths). The heavy, bony osteoderms have evolved independently in many different lineages. The armadillo osteoderm is believed to develop in subcutaneous dermal tissues. These varied structures should be thought of as anatomical analogues, not homologues, and do not necessarily indicate monophyly. The structures are however derived from scutes, common to all classes of amniotes and are an example of what has been termed deep homology. In many cases, osteoderms may function as defensive armor. Osteoderms are composed of bone tissue, and are derived from a scleroblast neural crest cell population during embryonic development of the organism. The scleroblastic neural crest cell population shares some homologous characteristics associated with the dermis. Neural crest cells, through epithelial-to-mesenchymal transition, are thought to contribute to osteoderm development.