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, 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 (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 Hypsodont. 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.
[Cooper, W. (1824). On the Remains of the Megatherium recently discovered in Georgia. Annals of the Lyceum of Natural History of New York, 1, 114-124.]
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 and bison.[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.[Lund, P. W. (1840). Nouvelles recherches sur la faune fossile du Brésil. In Annales des Sciences Naturelles (Vol. 13, pp. 310-319).][Schaub, S. (1935). Saugetierfunde aus Venezuela und Trinidad, Band 55. Kommissionsverlag von E.]
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.[Dugès, A. (1882). Nota sobre un fósil de Arperos. Estado de Guanajuato: El Minero Mexicano, 9(20), 233-235.] 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.[Mones, A. (1973). Note acerca de Eremotherium guanajuatense (Duges, 1882)(Edentata, Megatherioidea) de Araperos, estado de Guanajuato, México.] 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.
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.[Spillmann, F. (1948). Beitrge zur Kenntnis eines neuen gravigraden Riesensteppentieres (Eremotherium carolinenese gen. et. spec. nov.), seines Lebensraumes und seiner Lebensweise. Palaeobiologica, 8(3), 231-279.] 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 (Erēmos "Steppe", "desert") and θηρίον (Thērion "animal") after the landscape in Santa Elena Peninsula that E. carolinese was unearthed from.[Hoffstetter, R. (1949). Sobre los Megatheriidae del Pleistoceno del Ecuador, Schaubia, gen. nov. Boletín de Informaciones Científicas Nacionales, 3(25).] though the genus name was preoccupied, so it was renamed Schaubtherium the following year.[Hoffstetter, R. (1952). Les mammifères Pléistocènes de la République de l'Equateur. Soc.] Another dubious genus and species, Xenocnus cearensis, was dubbed in 1980 by Carlos de Paula Couto based on a partial Hamate bone (wrist bone), though he mistook as the astragalus (tarsal bone) of a megalochynid, that had been found in Pleistocene deposits in Itapipoca.
Classification
Eremotherium is a genus of the extinct ground sloth family Megatheriidae, which includes large to very large sloths in the group Folivora, which, together with the Megalonychidae and the Nothrotheriidae, form the superfamily Megatherioidea.
The Megatherioidea also includes the three-toed sloths of the genus
Three-toed sloth, one of the two sloth genera still alive today.
's closest relative in Megatheriidae is the namesake of the family
Megatherium, which was endemic to South America, slightly larger, and preferred more open habitats than
Eremotherium.
Pyramiodontherium and
Anisodontherium are also part of this subfamily, but are smaller and older, dating to the Late Miocene of Argentina. All of these genera belong to the subfamily
Megatheriinae, which includes the largest and most derived sloths. The direct phylogenetic ancestor of
Eremotherium is unknown, but may be linked to
Proeremotherium from the
Codore Formation in Venezuela, which dates to the Pliocene. The genus has numerous characteristics that are akin to those of
Eremotherium, but are more primitive.
Little is known about the evolution of the genus
Eremotherium. It may have evolved in the Early Pliocene in South America, where only a few sites from this period are known, and dispersed by crossing the Isthmus of Panama, i.e. the formation of the land bridge connecting North and South America, in the course of the Great American Biotic Interchange. The oldest fossils come from the Pliocene of the southern United States in North America, suggesting that the species instead evolved there before colonizing South America.
The discovery of
Proeremotherium also supports this hypothesis, indicating that these or other close ancestors of
Eremotherium first migrated to North America and evolved there, then moved back southward to South America after the formation of the Isthmus of Panama, similar to the glyptodont
Glyptotherium.
The following phylogenetic analysis of Megatheriinae within Megatheriidae was conducted by Brandoni et al., 2018
Description
Size
]]
Eremotherium was slightly larger than the closely related
Megatherium in size, reaching an overall length of and a height of while on all fours, possibly up to when it reared up on its hind legs.
Weight estimates for
Eremotherium have varied from .
A 2023 study by H. Gregory McDonald suggested an body mass of around
Another 2023 study, done by Barbosa and colleagues, considered the body mass estimate of around for fully grown adult
Eremotherium to be the most accurate estimate.
A 2024 study done by Dantas and colleagues, suggested than an average adult
Eremotherium weighed , within the range of .
In any case, it is one of the largest land-dwelling mammals of that time in
the Americas, along with
like
Mammoth,
Mastodon and
Gomphothere.
[Richard M. Fariña, Sergio F. Vizcaíno and Gerardo de Iuliis: Megafauna. Giant beasts of Pleistocene South America. Indiana University Press, 2013, pp. 1-436 (pp. 216-218) ISBN 978-0-253-00230-3][Sergio F. Vizcaíno, M. Susasna Bargo and Richard A. Fariña: Form, function, and paleobiology in xenarthrans. In: Sergio F. Vizcaíno and WJ Loughry (eds.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 86-99] As a ground-dwelling sloth, it had relatively shorter and stronger limbs compared to modern arboreal sloths and also had a longer tail.
[M Susana Bargo, Sergio F Vizcaíno, Fernando M Archuby and R Ernesto Blanco: Limb bone proportions, strength and digging in some Lujanian (Late Pleistocene-Early Holocene) mylodontid ground sloths (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 20(3), 2000, pp. 601-610]
Skull
The skull of
Eremotherium was large and massive, but lighter in build compared to
Megatherium. A complete skull measured 65 cm in length and was up to 33 cm wide at the
; at its highest, it reached 19 cm in height. The forehead line was clearly straight and not as wavy as in
Megatherium. The
nasal bone was shortened compared to the skull of
Megatherium, giving it an overall truncated cone appearance. Further differences to
Megatherium existed at the premaxillary bone: In
Eremotherium this had an overall triangular shape and was only loosely connected to the upper jaw, whereas in
Megatherium the premaxillary bone had a quadrangular shape, as well as a firm connection to the upper jaw.
[Cástor Cartelle and Gerardo De Iuliis: Eremotherium laurillardi: The Panamerican Late Pleistocene megatheriid sloth. Journal of Vertebrate Paleontology 15(4), 1995, pp. 830–841 ( online )] The
occipital bone is semicircular in posterior view and sloped backwards in lateral view. The articular surfaces as the point of attachment of the cervical spine curved far outwards and were relatively larger than in tree sloths and numerous other ground sloths. The
parietal bones had a far outward curved shape, which was partly caused by the large
cranial cavity with a volume of 1600 cm³. The strong zygomatic arch was closed, unlike today's sloths, but like the latter it had a massive bony outgrowth pointing downwards and backwards from the anterior base of the arch. In addition, a third outgrowth protruded diagonally upwards. The downward pointing bony process was clearly steeper than in other sloths. The
orbita was shallow and small and slightly lower than in
Megatherium or modern sloths.
[Franz Spillmann: Contributions to the knowledge of a new gravigrade giant steppe animal (Eremotherium carolinense gen. et sp. nov.), its habitat and its way of life. Palaeobiologica 8, 1948, pp. 231-279][Cástor Cartelle and Gerardo De Iuliis: Eremotherium laurillardi (Lund) (Xenarthra, Megatheriidae), the Panamerican giant ground sloth: Taxonomic aspects of the ontogeny of skull and dentition. Journal of Systematic Palaeontology 4 (2), 2006, pp. 199-209][Gerardo De Iuliis and Cástor Cartelle: A new giant megatheriine ground sloth (Mammalia: Xenarthra: Megatheriidae) from the late Blancan to early Irvingtonian of Florida. Zoological Journal of the Linnean Society 127, 1999, pp. 495-515][Virginia L Naples and Robert K McAfee: Reconstruction of the cranial musculature and masticatory function of the Pleistocene panamerican ground sloth Eremotherium laurillardi (Mammalia, Xenarthra, Megatheriidae). Historical Biology: An International Journal of Paleobiology 24 (2), 2012, pp. 187-206]
The lower jaw was about long, both halves were connected by a strong
symphysis, which extended forward in a spatulate shape and ended in a rounded shape. Typical for all representatives of the
Megatheriidae was the clearly downward curved course of the lower edge of the bone body, which resulted from the different length of the teeth. In
Eremotherium this caused the lower jaw to be deep below the symphysis, 15 cm below the second tooth and 12.5 cm below the fourth. The thickness of the curvature of the lower margin of the mandible increased significantly in the course of individual development, but the ratio of the height of the mandibular body to the length of the tooth row remained largely the same. This differs markedly from
Megatherium, in which the height of the mandible increased not only in absolute terms, but also relatively in relation to the length of the dentition.
[Cástor Cartelle, Gerardo De Iuliis and François Pujos: Eremotherium laurillardi (Lund, 1842) (Xenarthra, Megatheriinae) is the only valid megatheriine sloth species in the Pleistocene of intertropical Brazil: A response to Faure et al., 2014. Comptes Rendus Palevol 14, 2014, pp. 15-23] The mandibular body was also very thick, leaving little space for the tongue. The crown process rose up to , and the articular process was only slightly lower. At the posterior, lower end there was a strong, clearly notched angular process, the upper edge of which was approximately at the level of the masticatory plane. At the anterior edge of the lower jaw there was a strong
mental foramen. The dentition was typical for sloths, but in contrast to today's representatives it consisted of completely
Heterodont teeth, which is a characteristic feature of megatherians. Each branch of the jaw had 5 teeth in the upper jaw and 4 in the lower jaw, so in total
Eremotherium had 18 teeth. They resembled molars and, except for the front one, were quadrangular in shape, usually a good long in large individuals and very high-crowned (
hypsodont) with a height of . They had no roots and grew throughout their entire life. The
Tooth enamel was also missing. However, two transverse, sharp-edged ridges were typically formed on the chewing surface to help grind food. The entire upper row of teeth grew up to long, while the lower reached up to .
[Martine Faure, Claude Guérin and Fabio Parenti: Sur l'existence de deux specèces d'Eremotherium E. rusconii (Schaub, 1935) et E. laurillardi (Lund, 1842) dans le Pléistocène supérieur du Brésil intertropical. Comptes Rendus Palevol 13 (4), 2014, pp. 259-266][M. Susana Bargo, Gerardo de Iuliis and Sergio F. Vízcaino: Hypsodonty in Pleistocene ground sloths. Acta Palaeontologica Polonica 51 (1), 2006, pp. 53-61]
Postcrania
Almost all of the poscranial skeleton is known. The vertebrae were massively shaped, both at the vertebral bodies and at the lateral
Vertebra. However, the vertebral bodies were compressed in length, so that the tail appeared rather short overall and generally did not exceed the length of the lower limb sections.
It had 7
neck vertebrae. The
humerus represented a long tube with a bulky lower joint end. The total length was about . Distinctive, ridge-like muscle attachments on the middle shaft were typical. The forearm bones had much shorter lengths, with the spoke measuring about 67 cm, and the
ulna in length.
[Gerardo De Iuliis: Toward the morphofunctional understanding of the humerus of Megatheriinae: The identity and homology of some diaphyseal humeral features (Mammalia, Xenarthra, Megatheriidae). Senckenbergiana biologica 83, 2003, pp. 69-78] The
femur was massive, had the broad build characteristic of megatherians and was narrowed in front and behind. It had an average length of 74 cm, the largest bone found so far was long and wide. The third trochanter, a prominent muscle attachment point on the shaft, typical of xenarthrans, was absent in
Eremotherium as in all other megatherians. The
tibia and
fibula were only fused together at the upper end and not also at the lower end as in
Megatherium. In this case, the tibia became about 60 cm long.
[H. Gregory McDonald: Xenarthran skeletal anatomy: primitive or derived? Senckenbergiana biologica 83, 2003, pp. 5-17] The forelegs ended in hands with three fingers (III to V). The two inner phalanges (I and II) were fused together with some elements of the
carpus, such as the trapezium, to form a unit, the metacarpal-carpal complex (MCC).
[Gerardo De Iuliis and Cástor Cartelle: The medial carpal and metacarpal elements of Eremotherium and Megatherium (Xenarthra: Mammalia). Journal of Vertebrate Paleontology 14, 1994, pp. 525-533] Thus,
Eremotherium clearly deviates from
Megatherium and other closely related forms, which possessed four-fingered hands. In
Eremotherium, the
Metacarpal bones of the third digit was the shortest, measuring 19 cm in length, while those of the fourth and fifth were almost the same length, and respectively. The
Phalanx bone (the third phalanx) of the third and fourth fingers had a long and pointedly curved shape, which suggests correspondingly long claws. The fifth finger had only two phalanges and consequently no claw was formed there. (An exception is the older form
E. eomigrans, whose hands, in contrast to other megateria, were still five-fingered, with claws on digits I to IV.)
The foot, as in all megatheriids, was also three-fingered (digits III to V). It resembled the hand with an extremely short
metatarsal of the third finger. That of the fourth finger reached , that of the fifth in length.
Deviating from the hand, only the middle digit (III) had three phalanges with a terminal phalanx bearing a long claw. The two outer digit had only two phalanges. This structure of the foot is typical for evolved megatherians.
[Diego Brandoni, Alfredo A. Carlini, Francois Pujos, and Gustavo J. Scillato-Yané: The pes of Pyramiodontherium bergi (Moreno & Mercerat, 1891) (Mammalia, Xenarthra, Phyllophaga): The most complete pes of a Tertiary Megatheriinae. Geodiversitas 26 (4), 2004, pp. 643–659][François Pujos and Rodolfo Salas: A systematic reassessment and paleogeographic review of fossil Xenarthra from Peru. Bulletin de l'Institut Français d'Études Andines 33 (2), 2004, pp. 331-377]
Fossil distribution
Fossils of
Eremotherium have been found at over 130 sites.
The earliest species,
Eremotherium eomigrans is mainly known from Florida, with specimens also known from South Carolina as well as North Carolina, and dates from the late Pliocene to Middle Pleistocene.
[ ] is only known from a single femur found in Bolivia of an uncertain age, while
Eremotherium laurillardi is known from numerous fossils spanning from the late Pliocene to the end of the Pleistocene.
There is confusion regarding what records should be assigned to
E. eomigrans vs
E. laurillardi due to the skull, jaw and tooth anatomy of the two species being indistinguishable.
The range distribution of
Eremotherium laurillardi is the widest of any ground sloth, spanning from 30.5° S to 40.3°N. The northernmost record of the species is in New Jersey, which likely represents a northward extension of its range during a warm
interglacial period (probably the Last Interglacial/
Sangamonian, around 130-115,000 years ago), while the southernmost record of the genus is in Rio Grande do Sul in southernmost Brazil. Most records of
Eremotherium in Brazil are from the Brazilian Intertropical Region (BIR) in the east of the country,
and are particularly frequently found in tank deposits (infillings of small depressions caused by erosion).
Other records of the genus in North America north of Mexico are confined to the Gulf Coast and Southern Atlantic Coast, including
Texas, Florida,
South Carolina and Georgia.
[McDonald, H.G.; Lundelius, E.L., Jr. The giant ground sloth, Eremotherium laurillardi, (Xenarthra, Megatheriidae) in Texas. In Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael, O. Woodburne; Albright, L.B., III, Ed.; Museum of Northern Arizona Bulletin: Flagstaff, AZ, USA, 2009; Volume 65, pp. 407–421.] By the end of the Late Pleistocene
Eremotherium was probably absent from North America north of Mexico, though it maintained a wide distribution from Mexico to Brazil at the time of its extinction.
Most records of the genus in Mexico are from the southern and midlatitudes.
Fossils of
Eremotherium have been found at a wide range of altitudes, ranging from sea level to over .
Palaeobiology
Locomotion
The predominantly quadrupedal locomotion took place on inwardly turned feet, with the entire weight resting on the outer, fifth and possibly fourth phalanges (a pedolateral gait), whereby the
Talus bone was subject to massive reshaping.
[H. Gregory McDonald: Evolution of the Pedolateral Foot in Ground Sloths: Patterns of Change in the Astragalus. Journal of Mammal Evolution 19, 2012, pp. 209-215][Néstor Toledo, Gerardo De Iuliis, Sergio F. Vizcaíno and M. Susana Bargo: The Concept of a Pedolateral Pes Revisited: The Giant Sloths Megatherium and Eremotherium (Xenarthra, Folivora, Megatheriinae) as a Case Study. Journal of Mammalian Evolution 25 (4), 2018, pp. 525-537, doi:10.1007/s10914-017-9410-0] Likewise, the hands were turned inwards, in a position somewhat resembling the forefeet of the similarly clawed
Chalicotheriidae, a now extinct group of
Perissodactyla.
[Giuseppe Tito and Gerardo De Iuliis: Morphofunctional aspects and paleobiology of the manus in the giant ground sloth Eremotherium Spillmann 1948 (Mammalia, Xenarthra, Megatheriidae). Senckenbergiana biologica 83 (1), 2003, pp. 79-94] It also suggests that locomotion was rather slow. It was also unable to perform digging activities, as has been demonstrated for other large ground sloths, which can also be seen in the construction of the forearm, just as the manipulation of objects was minimised due to the limited ability of the fingers to move in relation to each other. However,
Eremotherium was able to stand up on its hind legs and pull branches and twigs with its hands, for example to reach the foliage of tall trees for feeding,
[Giuseppe Tito: New remains of Eremotherium laurillardi (Lund, 1842) (Megatheriidae, Xenarthra) from the coastal region of Ecuador. Journal of South American Earth Sciences 26, 2008, pp. 424-434] as well as make defensive strikes with its long claws.
The standing up was supported by the strong tail, similar to what is still the case today with
armadillos and
anteaters. The massive tail vertebrae in the front area of the tail suggest a strong musculature. Among other things, this concerns the
coccygeus muscle, which attaches to the
ischium and fixes the tail. Less well developed, on the other hand, were the epaxial muscles, which could cause the tail to straighten up.
Thermoregulation
While typically portrayed as furred annimals, some scientists suggested that large ground sloths were sparsely haired similar to that of elephants.
[Fariña, R. A. (2002). Megatherium, the hairless: appearance of the great Quaternary sloths (Mammalia; Xenarthra). Ameghiniana, 39(2), 241–244.] However, this was refuted by isotopic analysis, which argues that
Eremotherium and other ground sloths had metabolic rates similar to extant xenarthrans mammals. The authors suggested that
Eremotherium would’ve had body fur up to thick, although the fur density likely varied across its geographic range.
Social behaviour
Due to some group finds of several individuals at individual sites, such as in El Bajión in
Chiapas in
Mexico with four animals or in
Tanque Loma on the Santa Elena in
Ecuador with 22 individuals, some scientists discuss whether
Eremotherium possibly lived and roamed in small, herd-like groups.
[Bruno Andrés Than-Marchese, Luis Enrique Gomez-Perez, Jesús Albert Diaz-Cruz, Gerardo Carbot-Chanona and Marco Antonio Coutiño-José: Una nueva localidad con restos de Eremotherium laurillardi (Xenarthra: Megateriidae) in Chiapas, Mexico: possible evidence de gregarismo en la especie. VI Jornadas Paleontológicas y I Simposio de Paleontología en el Sureste de México: 100 years de paleontología en Chiapas, 2012, p. 50][Emily L Lindsey, Erick X Lopez Reyes, Gordon E Matzke, Karin A Rice, and H Gregory McDonald: A monodominant late-Pleistocene megafauna locality from Santa Elena, Ecuador: Insight on the biology and behavior of giant ground sloths. Palaeogeography, Palaeoclimatology, Palaeoecology, 2020, p. 109599,] Especially in Tanque Loma, the individuals recorded are composed of at least 15 adults and six juveniles. They were all found in close association in a single horizon, and they are interpreted as being contemporary with each other. The possible group was thought to have gathered at a waterhole and died there relatively abruptly due to an unknown event.
This fossil bed may suggest that
Eremotherium engaged in wallowing for thermoregulation purposes as seen with
Hippopotamus.
On the other hand, sometimes clustered occurrences of Eremotherium such as the 19 individuals from the sinkhole of Jirau in Brazil are considered to be accumulations over a long period of time.[Hermínio Ismael de Araújo-Júnior, Kleberson de Oliveira Porpino, Celso Lira Ximenes and Lílian Paglarelli Bergqvist: Unveiling the taphonomy of elusive natural tank deposits: A study case in the Pleistocene of northeastern Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology 378, 2013, pp. 52-74] In the case of the likewise giant ground sloth Lestodon from central South America, experts also interpret mass accumulations of remains of different individuals in part as evidence of phased group formation.[Rodrigo L. Tomassini, Claudia I. Montalvo, Mariana C. Garrone, Laura Domingo, Jorge Ferigolo, Laura E. Cruz, Dánae Sanz-Pérez, Yolanda Fernández-Jalvo, and Ignacio A. Cerda: Gregariousness in the giant sloth Lestodon (Xenarthra ): multi‑proxy approach of a bonebed from the Last Maximum Glacial of Argentine pampas. Scientific Reports 10, 2020, p. 10955, doi:10.1038/s41598-020-67863-0] Living tree sloths live solitary lives.[Adriano Garcia Chiarello: Sloth ecology. An overview of field studies. In: Sergio F. Vizcaíno and WJ Loughry (eds.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 269-280]
Diet
Eremotherium possessed extremely
Hypsodont, which, however, did not reach the dimensions of those of
Megatherium. As the teeth lack
Tooth enamel, this hypsodonty may not be an expression of specialisation on grass as food, unlike mammals with enamel in their teeth. The different expression of high-crownedness in the two large ground sloths is probably rather to be sought in adaptation to divergent habitats—more tropical lowlands in
Eremotherium and more temperate regions in
Megatherium.
From an
Anatomy point of view, the only moderately wide snout and the large total chewing surface of the teeth advocate a diet adapted to mixed plant foods. The average surface area of all teeth available for chewing food is 11,340 mm², which roughly corresponds to the values of the closely related
Megatherium, but clearly exceeds those of the
Lestodon, which is also giant but has a much broader snout. The latter genus belongs to the more distantly related
Mylodontidae and was probably a specialised grazer. Moreover, the total purchase area is within the range of variation of present-day
, some of which also prefer mixed plant diets.
[Sergio F Vizcaíno, M Susana Bargo and Guillermo H Cassini: Dental occlusal surface area in relation to body mass, food habits and other biological features in fossil xenarthrans. Ameghiniana 43 (1), 2006, pp. 11-26][Mário AT Dantas and Adaiana MA Santos: Inferring the paleoecology of the Late Pleistocene giant ground sloths from the Brazilian Intertropical Region. Journal of South American Earth Sciences 117, 2022, p.103899, doi:10.1016/j.jsames.2022.103899] Support for this view comes from various
Isotope analysis on the teeth of
Eremotherium. Thus, the animals probably fed on grass in rather open landscapes, but on foliage in largely closed forests.
[Mário André Trindade Dantas, Rodrigo Parisi Dutra, Alexander Cherkinsky, Daniel Costa Fortier, Luciana Hiromi Yoshino Kamino, Mario Alberto Cozzuol, Adauto de Souza Ribeiro and Fabiana Silva Vieira: Paleoecology and radiocarbon dating of the Pleistocene megafauna of the Brazilian Intertropical Region. Quaternary Research 79, 2013, pp. 61-65] Carbon isotopes and stereo microwear analysis suggest that an individual from the Late Pleistocene (34,705-33,947 cal yr
Before Present), of Goiás, Brazil, was a mixed feeder, suggesting a high proportion of shrubs and trees, this is in contrast to the presumed diet from specimens from Northeast Brazil, which had a diet of C4
Herbaceous plant plants.
Palaeopathologies
Numerous
Paleopathology have been described from
E. laurillardi fossils in the BIR. These documented ailments include
osteoarthritis and articular depressions, with spondyloarthropathy and calcium pyrophosphate deposition disease potentially present as well. These
are evidenced by the presence of osteophytes, bone overgrowth, bone erosion, and rough subchondral bone in various specimens.
is also the only xenarthran species from which linear defect is known.
Relationship with humans and extinction
The disappearance of
Eremotherium coincides with the end-Pleistocene extinction event, which post-dated arrival of humans in the Americas and saw the extinction of many
megafauna (large animals) across the Americas, which included other ground sloths as well as animals like
Glyptodont. One of the latest finds of
Eremotherium is from Ittaituba on Rio Tapajós, a tributary of the Amazon, that has an uncalibrated C14 date to 11,340 BP
(13,470 – 13,140 calibrated) and includes several skull and lower jaw fragments.
In a similar period, finds of
E. laurillardi at Barcelona in the Brazilian state of Rio Grande do Norte come from strata dating from 11,324 to 11,807 years ago.
A 2025 study suggested that
Eremotherium may have survived into the
Greenlandian to
Northgrippian, based on radiocarbon dating of three specimens of
E. laurillardi from the Jirau Paleontological Site, respectively dated to 6,208–7,714 calibrated (cal.) years
Before Present (BP), 7,867–8,536 cal. years BP and 6,120–7,427 cal. years BP.
There is no direct evidence of hunting by humans of
Eremotherium. A possible indication of interaction is a tooth of
Eremotherium that some authors have suggested had been modified by
Paleo-Indians, which was unearthed from a doline on the site of the São-José farm in the Brazilian state of Sergipe.
Some authors have regarded the idea as poorly evidenced, suggesting that the modification was more likely the result of natural processes,
while other authors supported the human modification hypothesis for this specimen based on six different techniques including stereomicroscopy, scanning electron microscopy, energy dispersive spectroscopy, ultraviolet photoluminescence analyses, synchrotron-based X-ray fluorescence and micro-CT scans.
Putative evidence of human modification were also reported in specimens of other Pleistocene
including the ground sloth
Glossotherium and the
glyptodont Neosclerocalyptus.
