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.
Smilodon is a genus of felids belonging to the extinct subfamily Machairodontinae. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats. Smilodon lived in the Americas during the Pleistocene epoch. The genus was named in 1842 based on fossils from Brazil; the generic name means "scalpel" or "two-edged knife" combined with "tooth". Three species are recognized today: S. gracilis, S. fatalis, and S. populator. The two latter species were probably descended from S. gracilis, which itself probably evolved from Megantereon. The hundreds of specimens obtained from the La Brea Tar Pits in Los Angeles constitute the largest collection of Smilodon fossils.
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.
Glyptodonts are an extinct clade of large, heavily armoured armadillos, reaching up to 1.5 metres (4.9 ft) in height, and maximum body masses of around 2 tonnes. They had short, deep skulls, a fused vertebral column, and a large bony carapace made up of hundreds of individual scutes. Some glyptodonts had clubbed tails, similar to ankylosaurid dinosaurs.
Mylodontidae is a family of extinct South American and North American ground sloths within the suborder Folivora of order Pilosa, living from around 23 million years ago (Mya) to 11,000 years ago. This family is most closely related to another family of extinct ground sloths, Scelidotheriidae, as well as to the extant arboreal two-toed sloths, family Choloepodidae; together these make up the superfamily Mylodontoidea. Phylogenetic analyses based on morphology uncovered the relationship between Mylodontidae and Scelidotheriidae; in fact, the latter was for a time considered a subfamily of mylodontids. However, molecular sequence comparisons were needed for the correct placement of Choloepodidae. These studies have been carried out using mitochondrial DNA sequences as well as with collagen amino acid sequences. The latter results indicate that Choloepodidae is closer to Mylodontidae than Scelidotheriidae is. The only other living sloth family, Bradypodidae, belongs to a different sloth radiation, Megatherioidea.
Castoroides, or giant beaver, is an extinct genus of enormous, bear-sized beavers that lived in North America during the Pleistocene. Two species are currently recognized, C. dilophidus in the Southeastern United States and C. ohioensis in most of North America. C. leiseyorum was previously described from the Irvingtonian age but is now regarded as an invalid name. All specimens previously described as C. leiseyorum are considered to belong to C. dilophidus.
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 at the end of the Late Pleistocene, 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.
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.
Glossotherium is an extinct genus of large mylodontid ground sloths of the subfamily Mylodontinae. It represents one of the best-known members of the family, along with Mylodon and Paramylodon. Reconstructed animals were between 3 and 4 metres long and possibly weighed up to 1,002.6–1,500 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, as far back Pliocene, about 3.3-3 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.
Acratocnus is an extinct genus of ground sloths that were found on Cuba, Hispaniola, and Puerto Rico.
Megalocnus is a genus of extinct ground sloths that were native to Cuba during the Pleistocene and Holocene epochs. They were among the largest of the Caribbean sloths (Megalocnidae), with individuals estimated to have weighed up to 270 kg to 200 kg, around the size of a black bear when alive. Its relatives include other megalocnid sloths, such as Acratocnus, Mesocnus, Miocnus, Neocnus andParocnus. The former species M. zile from Hispaniola is currently thought to be a junior synonym of Parocnus serus.
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.
Thalassocnus is an extinct genus of semiaquatic ground sloths from the Miocene and Pliocene of the Pacific South American coast. It is monotypic within the subfamily Thalassocninae. The five species—T. antiquus, T. natans, T. littoralis, T. carolomartini, and T. yuacensis—represent a chronospecies, a population gradually adapting to marine life in one direct lineage. They are the only known aquatic sloths, but they may have also been adapted to a terrestrial lifestyle. They have been found in the Pisco Formation of Peru, the Tafna Formation of Argentina, and the Bahía Inglesa, Coquimbo, and Horcón formations of Chile. Thalassocninae has been placed in both the families Megatheriidae and Nothrotheriidae.
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 Brazil, Uruguay, Paraguay, Bolivia, Peru, Argentina, and Colombia. 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.
Arctodus is an extinct genus of short-faced bear that inhabited North America during the Pleistocene. There are two recognized species: the lesser short-faced bear and the giant short-faced bear. Of these species, A. simus was larger, is known from more complete remains, and is considered one of the most charismatic of North America's megafauna. A. pristinus was largely restricted to the Early Pleistocene of the Eastern United States, whereas A. simus had a broader range, with most finds being from the Late Pleistocene of the United States, Mexico and Canada. A. simus evolved from A. pristinus, but both species likely overlapped in the Middle Pleistocene. Both species are relatively rare in the fossil record.
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.
The mammalian order Pilosa, which includes the sloths and anteaters, includes various species from the Caribbean region. Many species of sloths are known from the Greater Antilles, all of which became extinct over the last millennia, but some sloths and anteaters survive on islands closer to the mainland.
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.
Megalocnidae is an extinct family of sloths, native to the islands of the Greater Antilles from the Early Oligocene to the Mid-Holocene. They are known from Cuba, Hispaniola and Puerto Rico, but are absent from Jamaica. While they were formerly placed in the Megalonychidae alongside two-toed sloths and ground sloths like Megalonyx, recent mitochondrial DNA and collagen sequencing studies place them as the earliest diverging group basal to all other sloths. or as an outgroup to Megatherioidea. They displayed significant diversity in body size and lifestyle, with Megalocnus being terrestrial and probably weighing several hundred kilograms, while Neocnus was likely arboreal and similar in weight to extant tree sloths, at less than 10 kilograms.
