Eremotherium
Eremotherium 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, Eremotherium migrated northwards into North America as part of the Great American Interchange 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 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. 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 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. 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 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. 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. They also have been referred to Eremotherium laurillardi. For many years, E. laurillardi
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
File:Giant ground sloth.jpg|thumb|243x243px|E. eomigrans at the NCMNS, depicted as inhabiting a longleaf pine savanna.
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 layers of Newberry, Florida, USA, though many other fossils from the area were referred to it. Many of the fossils were isolated and had been recovered from sinkholes, river canals, shorelines, and hot springs, with few of the specimens being associated skeletons. So far, the latter has only been found in North America and reached a size similar to E. laurillardi, but comes from the Pliocene and Early Pleistocene and bears a pentadactyl, or five fingered, hand in contrast to the tridactyl hands of Megatherium and E. laurillardi.
The genus name Eremotherium was not erected until 1948 by Franz Spillmann, erecting a new species, E. carolinese, as the type species of the genus based on a 65 cm long skull with associated lower jaw, both fossils come from the Santa Elena Peninsula in Ecuador, and the species name was after the local village of Carolina. Although it was the type species of the genus for many years, the species has since been synonymized with E. laurillardi and has been replaced by it as the type species. The generic name Eremotherium is derived from the Greek words ἔρημος and θηρίον after the landscape in Santa Elena Peninsula that E. carolinese was unearthed from. The following year, French taxonomist Robert Hoffstetter introduced the genus Schaubia for Samuel Schaub's Megatherium rusconii because he recognized its generic distinctness from Megatherium, though the genus name was preoccupied, so it was renamed Schaubtherium the following year. It was not until 1952 that he recognized similarities to Spillmann's Eremotherium and synonymized the two. Another dubious genus and species, Xenocnus cearensis, was dubbed in 1980 by Carlos de Paula Couto based on a partial unciform, though he mistook as the astragalus of a megalochynid, that had been found in Pleistocene deposits in Itapipoca, Brazil. Paula Couto even created a new subfamily, Xenocninae, for the genus, but reanalysis in 2008 proved that the fossil was instead from Eremotherium laurillardi.