Eremotherium

''Eremotherium'' (from Greek for "steppe" or "desert" "beast": ἔρημος "steppe or desert" and θηρίον "beast") is an extinct genus of giant ground sloth in the family Megatheriidae. ''Eremotherium'' lived in southern North America, Central America, and northern South America. It was one of the largest sloths, with a body size comparable to elephants, weighing around and measuring about long, slightly larger than its close relative ''Megatherium''.

Originating during the Pliocene of fauna between North and South America following the emergence of the Isthmus of Panama during the late Pliocene. Finds of ''Eremotherium'' are common and widespread, with fossils being found as far north as South Carolina (with a single record also reported from New Jersey) in the United States and as far south as Rio Grande Do Sul in southern Brazil, and many complete skeletons have been unearthed.

''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. 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 that adapted its diet to local environments and climates. Like ''Megatherium, Eremotherium'' is suggested to have been capable of adopting a bipedal posture to feed on high-growing leaves.

Only two valid species are known, ''Eremotherium laurillardi'' and ''E. eomigrans,'' the former was named by prolific Danish paleontologist Peter Lund in 1842 based on a tooth of a juvenile individual that had been collected from Pleistocene deposits in caves in Lagoa Santa, Brazil alongside fossils of thousands of other megafauna. Lund originally named it as a species of its relative ''Megatherium'', though Austrian paleontologist Franz Spillman later created the genus name ''Eremotherium'' after noticing its distinctness from other megatheriids.

''Eremotherium'' became extinct at the end of the Late Pleistocene as part of the end-Pleistocene extinction event, alongside other ground sloths and most large mammals across the Americas, though some specimens potentially suggest that ''Eremotherium'' might have lived up to the early-middle Holocene. The extinction of ''Eremotherium'' and other megafauna post-dates human arrival in the Americas, who may have contributed to the extinctions. Some potential, but not definitive evidence has been found for the interaction between humans and ''Eremotherium'' remains. Some potential early-middle Holocene records of ''Eremotherium'' have been reported from Brazil.

History and naming

The taxonomic history of ''Eremotherium'' largely involves it being confused with ''Megatherium'' and the naming of many additional species that are actually synonymous with ''E. laurillardi.'' For many years fossils from the genus have been known, with records from as early as 1823 when fossil collectors J. P. Scriven and Joseph C. Habersham collected several teeth, skull, and mandible fragments, including a nearly complete set of mandibles, from Quaternary age deposits in Skidaway Island, Georgia in the United States. The fossils were not described until 1852 however, when American paleontologist named ''Megatherium mirabile'', based on the specimens (specimen numbers USNM 825-832 + 837) but the species has since been synonymized with ''Eremotherium laurillardi''. The first published discovery was only a year after ''M. mirabile'' was discovered, when portions of 2 teeth that had been also collected from Skidaway Island were referred to ''Megatherium'' later in 1823 by Dr. Samuel L. Mitchell.Hodgson, W. B., & Habersham, J. C. (1846). ''Memoir on the Megatherium, and Other Extinct Gigantic Quadrupeds of the Coast of Georgia: With Observations on Its Geologic Feature'' (Vol. 10). Barlett & Welford. 20 more fossils from the island were reported in 1824 by naturalist William Cooper, including mandibular, limb, and dental remains, that now reside at the Lyceum of Natural History in New York, that had also been collected by Joseph C. Habersham.

Several other discoveries from Georgia and South Carolina were described as ''Megatherium'' throughout the 1840s and 1850s, like in 1846 when Savannah scholar William B. Hodgson described some "''Megatherium''" fossils from Georgia that had been donated by Habersham, including portions of several skulls, in a collection that included fossils of several other Pleistocene megafauna like mammoths and bison. These were all described in more detail by Joseph Leidy in 1855, but they were not all referred to ''Eremotherium'' until the late 20th century. In 1842, Richard Harlan named a new species of the turtle ''Chelonia, Chelonia couperi'', based on a supposed femur, or thigh bone, that had been found in the Brunswick Canal in Glynn County, Georgia and dated to the Pleistocene. It was not until 1977 that further analysis demonstrated that the "femur" was actually a clavicle from ''Eremotherium''. It is unknown, which publication was published first - according to the regulations of the ICZN, the species name of the first publication would have priority, even if it was attached to another genus - but the species name ''E. couperi'' is rarely used, while ''E. laurillardi'' is more widely used and has been adopted by more scientists.

Fossils from South America were first described by Danish paleontologist and founder of Brazilian paleontology Peter Wilhelm Lund when he established a new species of ''Megatherium'' based on two teeth (specimen number ZMUC 1130 and 1131) from Lapa Vermella, a cave in the valley of the Rio de la Velhas in the Brazilian state of Minas Gerais under the name ''Megatherium laurillardi'', the first named species now assigned to ''Eremotherium''. Lund diagnosed the species based on the size of the teeth, which were only a quarter the size of ''Megatherium americanum'', the greatest representative of ''Megatherium'', and he believed that it was a tapir-sized animal.Lund, P.W., 1842. Blik paa Brasiliens Dyreverden för Sidste Jordomvaeltning. Tredie Afhandling: Forsaettelse af Pattedyrene. Det Kongel. Danske Vidensk. Selsk. Skr. Naturvidensk. Math. Afd. 9, 137–208. Today, the teeth are considered to be from a juvenile of ''E. laurillardi'' and adults reached or exceeded the size of ''M. americanum''. Two years earlier, Lund had already figured teeth found at Lapa Vermella, which he assigned to ''Megatherium americanum'' due to their dimensions, which he figured alongside those of ''M. laurillardi'' in the 1842 publication.Lund, P. W. (1840). Nouvelles recherches sur la faune fossile du Brésil. In ''Annales des Sciences Naturelles'' (Vol. 13, pp. 310-319). They also have been referred to ''Eremotherium laurillardi''. For many years, ''E. laurillardi'''s holotype was speculated to actually have come from a dwarf species of ''Eremotherium'' while the larger fossils belonged to another distinct species like ''E. rusconii,'' a species that was erected by Samuel Schaub in 1935 for giant fossils from Venezuela, though it was initially thought to be a species of ''Megatherium''. However, this view is mostly contradicted and argues that at least in the Late Pleistocene in South and North America there was only a single species, ''E. laurillardi'', which had a strong sexual dimorphism. Discoveries of extensive material of ''Eremotherium'' at sites such as those at Nova Friburgo in Brazil and Daytona Beach in Florida further prove that the two were synonymous and lacked any major differences between populations.

Fossils of ''Eremotherium'' from Mexico were first described in 1882 by French scientist Alfred Duges, though they consisted only of a fragmentary left femur, as a new species of the South American '' Scelidotherium'', naming it ''S. guanajatense.'' The femur had been found in Pleistocene deposits in Guanajuato, Mexico, but the fossil has since been lost and the species is a synonym of ''E. laurillardi.'' Another species that might be considered valid was described in 1997 by Canadian zoologist Gerardo De Iuliis and French paleontologist Pierre-Antoine St-Andréc based on a single, approximately 39 cm long femur from the Pleistocene strata in Ulloma, Bolivia as ''Eremotherium sefvei,'' though it was first described in 1915 as a fossil of ''Megatherium''. ''E. sefvei'''s geologic aging is less definite can only be placed in the general Pleistocene, but it is the smallest representative of ''Eremotherium'' and all post-Miocene megatheriids. In 2018, De Iuliis (one of the original describers of ''E. sefvei'') noted that while its validity cannot be entirely precluded, the features of this species were not beyond the range of variation known among other megatheriines, with the type specimen bearing similarity to the specimen of ''Megatherium medinae''.

Two years later in 1999, De Iuliis and Brazilian paleontologist Carlos Cartelle erected another species of ''Eremotherium'' now seen as valid, ''E. eomigrans'', based on a partial skeleton, the holotype, that had been unearthed from the latest Blancan

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