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 60million 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 Mya, 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.
Megatherium is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Pleistocene. It is best known for the elephant-sized type species M. americanum, sometimes called the giant ground sloth, or the megathere, native to the Pampas through southern Bolivia during the Pleistocene. Various other smaller species belonging to the subgenus Pseudomegatherium are known from the Andes.
Mylodon is a genus of extinct ground sloth belonging to the family Mylodontidae, known from the region of Patagonia in Chile and Argentina in southern South America. With a total length of 3 to 4 m, it is one of the best-known and largest representatives of the group. The oldest finds probably date to the Lower Pleistocene; however, most of the fossil remains date from the Upper Pleistocene period. One of the most important sites of this phase is the Cueva del Milodón in southern Chile. Shortly after, about 10,200 BP, Mylodon became extinct. At this point in time, it coexisted with the first human colonists in America. However, there is little evidence that it was hunted by humans.
Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Caribbean ground sloths, the most recent survivors, lived in the Antilles, possibly until 1550 BCE. However, radiocarbon dating suggests an age of between 2819 and 2660 BCE for the last occurrence of Megalocnus in Cuba. Ground sloths had been extinct on the mainland of North and South America for 10,000 years or more. They survived 5,000–6,000 years longer in the Caribbean than on the American mainland, which correlates with the later colonization of this area by humans.
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 actually 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.
Glyptotherium is a genus of glyptodont that lived from the Early Pliocene, about 4.9 million years ago, to the Early Holocene, around 7,000 years ago, 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, G.texanum. The holotype included a nearly complete carapace, tail, or caudal, armor, and several additional postcranial elements that had been found in the Pliocene Blancan Beds in Llano Estacado, Texas, USA. The genus has since been discovered from many more fossil sites. Another species, G. cylindricum, was named in 1912 by fossil hunter Barnum Brown on the basis of a partial carapace, teeth, and several additional fossils that had been unearthed from the Pleistocene deposits in Jalisco, Mexico.
Glossotherium is an extinct genus of mylodontid ground sloths of the subfamily Mylodontinae, which includes large ground-dwelling sloths. It represents one of the best known members of the family, along with Mylodon and Paramylodon. Reconstructed animals were between 3 to 4 metres long and possibly weighed up to 1700 kg. The majority of finds of Glossotherium date from the Middle and Upper Pleistocene, around 300,000 to 10,000 years ago, with a few dating older, possibly as far back as the Pliocene, about 3 million years ago. The range included large parts of South America, east of the Andes roughly from latitude 20 to 40 degrees south, leaving out the Amazon Basin in the north. In western South America, finds are also documented north of the equator. The animals largely inhabited the open landscapes of the Pampas and northern savanna regions.
Eremotherium is an extinct genus of giant ground sloth, in the family Megatheriidae, the largest and most heavily built family of sloths. Eremotherium lived in the southern parts of North America and the northern parts of 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. 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 a pure herbivore who dined on leaves and grasses, though it may have had semi-aquatic habits like modern hippos based on isotopic data. 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–11,000 years ago. It is also known as Harlan's ground sloth.
Nothropus is an extinct genus of ground sloth of the family Nothrotheriidae, endemic to South America during the Pleistocene epoch. It lived from 0.781 mya—12,000 years ago existing for approximately 0.769 million years. It was believed to be a ground-dwelling herbivore.
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.
Scelidodon is an extinct genus of South American ground sloths. Its remains have been found in the Yupoí and Uspara Formations of Argentina, the Ulloma, Umala, Ñuapua and Tarija Formations of Bolivia, in Brazil, in Chile and in Peru. The youngest fossils have been dated to as recently as 9000 B.P.
Mylodontinae is an extinct subfamily of ground sloths that lived from the Early Miocene to the Early Holocene epochs.
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.
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.
Archaeomylodon is an extinct genus of mylodontine ground sloths that lived during the Middle Pleistocene of what is now Argentina. It is known so far only from a single skull, which in its dimensions corresponds to those of the giant Lestodon. However, the skull differs from this one by its narrower and higher snout. In addition, the anterior canine teeth, which are usually large in many mylodonts, are greatly reduced. The find comes from the Pampa region of South America and was deposited in about 700,000 years old sediments.
Urumacotherium is an extinct genus of ground sloths of the family Mylodontidae. It lived from the Middle Miocene to the Early Pliocene of what is now Brazil, Peru and Venezuela.
Simomylodon is an extinct genus of ground sloths from the family Mylodontidae. It lived from the Late Miocene to the Middle Pliocene of what is now Bolivia and Argentina, 5.3 to 2.8 million years ago. The most important find material comes from the central Altiplano in Bolivia and includes several skulls and dentition remains. Thus, the so far documented body skeleton is the best known and most significant of a Miocene representative of the Mylodontidae. On the basis of the remains, it can be concluded that it is a rather small member of the Mylodontidae. The construction of the limbs supports ground-dwelling locomotion, but this does not exclude occasional digging or climbing. The type and only known species is Simomylodon uccasamamensis.
