Xenarthra is a 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. 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.
Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. Ground sloths varied widely in size, with the largest genera Megatherium and Eremotherium being around the size of elephants. Ground sloths are a paraphyletic group, as living tree sloths are thought to have evolved from ground sloth ancestors.
Scelidotheriidae is a family of extinct ground sloths within the order Pilosa, suborder Folivora and superfamily Mylodontoidea, related to the other extinct mylodontoid family, Mylodontidae, as well as to the living two-toed sloth family Choloepodidae. The only other extant family of the suborder Folivora is the distantly related Bradypodidae. Erected as the family Scelidotheriidae by Ameghino in 1889, the taxon was demoted to a subfamily of Mylodontidae by Gaudin in 1995. However, recent collagen sequence data indicates the group is less closely related to Mylodon and Lestodon than Choloepus is, and thus it has been elevated back to full family status by Presslee et al. (2019).
Megalonyx is an extinct genus of ground sloths of the family Megalonychidae, native to North America. It evolved during the Pliocene Epoch and became extinct during the Quaternary extinction event at the end of the Late Pleistocene-Early Holocene, living from ~5 million to ~13,000 years ago. The type species, M. jeffersonii, the youngest and largest known species, measured about 3 meters (9.8 ft) in length and weighed up to 1,000 kilograms (2,200 lb).
Megalonychidae is an extinct family of sloths including the extinct Megalonyx. Megalonychids first appeared in the early Oligocene, about 35 million years (Ma) ago, in southern Argentina (Patagonia). There is, however, one possible find dating to the Eocene, about 40 Ma ago, on Seymour Island in Antarctica. They first reached North America by island-hopping across the Central American Seaway, about 9 million years ago, prior to formation of the Isthmus of Panama about 2.7 million years ago. Some megalonychid lineages increased in size as time passed. The first species of these were small and may have been partly tree-dwelling, whereas the Pliocene species were already approximately half the size of the huge Late Pleistocene Megalonyx jeffersonii from the last ice age.
Sloths are a Neotropical group of xenarthran mammals constituting the suborder Folivora, including the extant arboreal tree sloths and extinct terrestrial ground sloths. Noted for their slowness of movement, tree sloths spend most of their lives hanging upside down in the trees of the tropical rainforests of South America and Central America. Sloths are considered to be most closely related to anteaters, together making up the xenarthran order Pilosa.
Glyptotherium is a genus of glyptodont in the family Chlamyphoridae that lived from the Early Pliocene, about 3.6 million years ago, to the Late Pleistocene, around 15,000 years ago. It had a wide distribution, living in the United States, Mexico, Guatemala, Costa Rica, Honduras, El Salvador, Panama, Venezuela, and Brazil. The genus was first described in 1903 by American paleontologist Henry Fairfield Osborn with the type species being, G. texanum, based on fossils that had been found in the Pliocene Blancan Beds in Llano Estacado, Texas, USA. Glyptotherium fossils have since been unearthed from many more fossil sites, from Florida to Colombia. 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, with G. texanum being from the older Early Pliocene to Early Pleistocene strata, whereas G. cylindricum is exclusive to the Late Pleistocene.
Nothrotheriops is a genus of Pleistocene ground sloth found in North America, from what is now central Mexico to the southern United States. This genus of bear-sized xenarthran was related to the much larger, and far more famous Megatherium, although it has recently been placed in a different family, Nothrotheriidae. The best known species, N. shastensis, is also called the Shasta ground sloth.
Eremotherium is an extinct genus of giant ground sloth in the family Megatheriidae. Eremotherium lived in the southern North America, Central America, and northern South America from the Pliocene, around 5.3 million years ago, to the end of the Late Pleistocene, around 10,000 years ago. Eremotherium was widespread in tropical and subtropical lowlands and lived there in partly open and closed landscapes, while its close relative Megatherium lived in more temperate climes of South America. Both genera reached the size of today's elephants and were among the largest mammals in the Americas. Characteristic of Eremotherium was its robust physique with comparatively long limbs and front and hind feet especially for later representatives- three fingers. However, the skull is relatively gracile, the teeth are uniform and high-crowned. Like today's sloths, Eremotherium was purely herbivorous and was probably a mixed feeder that dined on leaves and grasses. Eremotherium was a generalist that could adapt its diet to the respective local and climatic conditions of many regions. Finds of Eremotherium are common and widespread, with fossils being found as far north as South Carolina in the United States and as far south as Rio Grande Do Sul, and many complete skeletons have been unearthed.
Paramylodon is an extinct genus of ground sloth of the family Mylodontidae endemic to North America during the Pliocene through Pleistocene epochs, living from around ~4.9 Mya–12,000 years ago.
Holmesina is a genus of pampathere, an extinct group of armadillo-like creatures that were distantly related to extant armadillos. Like armadillos, and unlike the other extinct branch of megafaunal cingulates, the glyptodonts, the shell was made up of flexible plates which allowed the animal to move more easily. Holmesina species were herbivores that grazed on coarse vegetation; armadillos are mostly insectivorous or omnivorous.
Catonyx is an extinct genus of ground sloth of the family Scelidotheriidae, endemic to South America during the Pliocene and Pleistocene epochs. It lived from 2.5 Ma to about 10,000 years ago, existing for approximately 2.49 million years. The most recent date obtained is about 9600 B.P.
Ahytherium is an extinct genus of megalonychid sloth that lived during the Pleistocene of what is now Brazil. It contains a single species, A. aureum.
Nothrotheriidae is a family of extinct ground sloths that lived from approximately 17.5 mya—10,000 years ago, existing for approximately 17.49 million years. Previously placed within the tribe Nothrotheriini or subfamily Nothrotheriinae within Megatheriidae, they are now usually placed in their own family, Nothrotheriidae. Nothrotheriids appeared in the Burdigalian, some 19.8 million years ago, in South America. The group includes the comparatively slightly built Nothrotheriops, which reached a length of about 2.75 metres (9.0 ft). While nothrotheriids were small compared to some of their megatheriid relatives, their claws provided an effective defense against predators, like those of larger anteaters today.
Australonyx is an extinct genus of ground sloths, endemic to South America during the Late Pleistocene. It was found in Brazil.
Valgipes is an extinct genus of scelidotheriid ground sloth, endemic to intertropical Brazil and Uruguay during the Late Pleistocene. Thought to have been a forest-dwelling browser, Valgipes is a monotypic genus with a complex and long taxonomic history, and is a close relative of Catonyx and Proscelidodon.
Xibalbaonyx is an extinct genus of megalonychid ground sloth known from the Late Pleistocene of Mexico. Three species are known: X. oviceps and X. exiniferis from the Yucatan peninsula and X. microcaninus from Jalisco. The genus is named after Xibalba, the underworld in Maya mythology.
Nohochichak is an extinct genus of megalonychid ground sloth from the Late Pleistocene (Rancholabrean) of the Yucatan Peninsula in Mexico.
Lakukullus is an extinct genus of nothrotheriid ground sloths that lived during the Middle Miocene around 13.8 to 11.8 million years ago of what is now Bolivia.
Ortotherium is a genus of megalonychid ground sloth from the Late Miocene Ituzaingó Formation of Entre Rios Province, Argentina. Although many species were described, the only valid species of the genus is Ortotherium laticurvatum, with many species being junior synonyms. Ortotherium is known from very fragmentary material, all of which is material from the mandible and teeth. The holotype of O. laticurvatum consists of an incomplete left dentary that had been unearthed from a series of sediments known as ‘Conglomerado osifero’ in Paraná, Argentina. Argentina paleontologist Florentino Ameghino named the species in 1885, though he would go on to name four more, invalid, species of the genus. One species however, O. brevirostrum, has been reclassified as Mesopotamocnus.
