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 known as 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.
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.
Megatheriidae is a family of extinct ground sloths that lived from approximately 23 mya—11,000 years ago.
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).
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.
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.
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.
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.
Diabolotherium is an extinct genus of megatheriine ground sloth, known from the Late Pleistocene of Peru. Unlike most other extinct mainland sloths, it seems to have been a climber, similar to extinct sloths from the Caribbean. Fossils of the genus were found at the coastal Piedra Escrita site and the Andean Casa del Diablo cave.
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.
Nohochichak is an extinct genus of megalonychid ground sloth from the Late Pleistocene (Rancholabrean) of the Yucatan Peninsula in Mexico.
Megatheriinae is a subfamily of the Megatheriidae, an extinct family of ground sloths that lived from the Middle Miocene to the Early Holocene.
Megathericulus is an extinct genus of ground sloths in the Megatheriidae family. It lived during the Middle Miocene, 11-16 Ma in what is now South America. Fossils have been found principally in Argentina, Bolivia, and Peru. It is a smaller representative of the megatheres. Despite being one of the earliest-known members of the family, its dentition structure is associated with homodont teeth belonging to the more modern line of evolution. The genus was scientifically named in 1904. Only one species is currently recognized, Megathericulus patagonicus.
Proeremotherium is an extinct genus of megatheriine ground sloths in the family Megatheriidae. It lived during the Late Miocene and Early Pliocene of what is now Venezuela. So far, two largely complete skulls have been recovered in the Falcón Basin in Venezuela. The finds identify the animals as medium-sized representatives of the Megatheriidae. In the cranial anatomy, Proeremotherium resembles the later and giant Eremotherium. It is therefore assumed that the two ground sloths are directly related to each other.
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.
Aymaratherium is an extinct genus of nothrotheriid ground sloths that lived during the Late Miocene and Early Pliocene of Bolivia. Fossils of Aymaratherium have been found in the Pomata Ayte locality of the Umala Formation.
Mesopotamocnus is an extinct genus of megalonychid ground sloth that lived during the Late Miocene in what is now Argentina. Fossils have been found in the Ituzaingó Formation of Argentina.
Bolivartherium is an extinct genus of mylodontine mylodontid sloth that lived during the Late Miocene and Late Pliocene in what is now Venezuela. Fossils have been found in the Codore and Urumaco Formations of Venezuela.
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.
