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Megatherium

Megatherium (/mɛɡəˈθɪəriəm/ meg-ə-THEER-ee-əm; from Greek méga (μέγα) 'great' + theríon (θηρίον) 'beast') is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene[1] through the end of the Pleistocene.[2] 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.

Megatherium
Temporal range: Early Pliocene[1] to Early Holocene, 5–0.010 Ma
Possible later date of 0.008 Ma
M. americanum skeleton, Natural History Museum, London
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Pilosa
Clade: Megatheria
Family: Megatheriidae
Subfamily: Megatheriinae
Genus: Megatherium
Cuvier, 1796
Type species
Megatherium americanum
Cuvier, 1796
Subgenera
Megatherium
  • M. altiplanicum Saint-Andre & De Iuliis, 2001
  • M. americanum Cuvier, 1796
Pseudomegatherium
  • M. celendinense Pujos, 2006
  • M. medinae Philippi, 1893
  • M. sundti Philippi, 1893
  • M. tarijense Gervais & Ameghino, 1880
  • M. urbiani Pujos & Salas, 2004
Map showing the distribution of all Megatherium species in red, inferred from fossil finds
Synonyms
  • Essonodontherium Ameghino 1884
  • Orocanthus Ameghino 1885
  • Neoracanthus Ameghino 1889

Megatherium is part of the sloth family Megatheriidae, which also includes the similarly giant Eremotherium, comparable in size to M. americanum, which was native to tropical South America, Central America and North America as far north as the southern United States. Megatherium was first discovered in 1788 on the bank of the Luján River in Argentina. The holotype specimen was then shipped to Spain the following year wherein it caught the attention of the paleontologist Georges Cuvier, who was the first to determine, by means of comparative anatomy, that Megatherium was a sloth.[3] Megatherium became extinct around 12,000 years ago as part of the Late Pleistocene extinctions, simultaneously with the majority of other large mammals in the Americas. The extinctions followed the first arrival of humans in the Americas, and one and potentially multiple kill sites where M. americanum was slaughtered and butchered is known, suggesting that hunting could have caused its extinction.[4]

Taxonomy

Megatherium is divided into 2 subgenera, Megatherium and Pseudomegatherium. Taxonomy according to Pujos (2006) and De Iuliis et al (2009):[5][6]

  • Subgenus Megatherium
    • M. altiplanicum Saint-André & de Iuliis 2001
    • M. americanum Cuvier 1796
  • Subgenus Pseudomegatherium Kraglievich 1931
    • M. celendinense Pujos 2006
    • M. medinae Philippi 1893
    • M. sundti Philippi 1893
    • M. tarijense Gervais & Ameghino, 1880
    • M. urbinai Pujos & Salas 2004
 
Specimen of M. americanum in Museo Nacional de Ciencias Naturales, Madrid, the first prehistoric animal skeleton mounted, in 1795.

The first fossil specimen of Megatherium was discovered in 1788 by Manuel Torres, on the bank of the Luján River in Argentina. The fossil was shipped to Museo Nacional de Ciencias Naturales in Madrid the following year, where it remains. It was reassembled by museum employee Juan Bautista Bru, who also drew the skeleton and some individual bones.[7]

Based on Bru's illustrations, comparative anatomist Georges Cuvier determined the relationships and appearance of Megatherium. He published his first paper on the subject in 1796,[8] a transcript of a previous lecture at the French Academy of Sciences. He published on the subject again in 1804; this paper was republished in his book Recherches sur les ossemens fossiles de quadrupèdes.[3][8] In his 1796 paper, Cuvier assigned the fossil the scientific name Megatherium americanum. Cuvier determined that Megatherium was a sloth, and at first believed that it used its large claws for climbing trees, like modern sloths, although he later changed his hypothesis to support a subterranean lifestyle, with the claws used to dig tunnels.[3]

Fossils of Megatherium and other western megafauna proved popular with the Georgian-era public, preceding the discovery of giant dinosaurs some decades later.

Since the original discovery, numerous other fossil Megatherium skeletons have been discovered across South America, in Argentina, Bolivia, Brazil, Chile, Colombia (Quipile, Cundinamarca),[9][10] Guyana, Paraguay, Peru and Uruguay.[2] New species in the genus Megatherium, M. urbinai and M. celendinense, have been described in 2004 and 2006, respectively.[11] M. celedinense is named after Celendin, Cajamarca Province in the Peruvian Andes.[5] These species are considerably smaller than M. americanum, and are considered to belong to a separate subgenus, Pseudomegatherium.[5]

The species Megatherium (Pseudomegatherium) tarijense, appears to be a junior synonym of M. americanum, and merely a small individual.[12]

The species Megatherium filholi Moreno, 1888 of the Pampas, previously thought to be a junior synonym of M. americanum representing juvenile individuals, was suggested to be a distinct valid species in 2019.[13]

Megatherium gallardoi Ameghino & Kraglievich 1921 from the Ensenadan of Argentina was suggested to be a valid species in 2008, most closely related to M. americanum and M. altiplanicum.[14]

M. parodii Hoffstetter 1949, and M. istilarti Kraglievich 1925 have not had their validity assessed in recent literature.

Evolution

 
Bru's 1796 skeletal drawing of M. americanum

Ground sloths are a diverse group belonging to superorder Xenarthra, which also includes extinct pampatheres and glyptodonts, as well as living tree sloths, anteaters and armadillos. One of the four major eutherian radiations, this superorder evolved in isolation in South America while it was an island continent during the Paleogene and Neogene. The family to which Megatherium belongs, Megatheriidae, is related within superfamily Megatherioidea to the extinct families Nothrotheriidae and Megalonychidae, and to living three-toed sloths of family Bradypodidae, as deduced recently from collagen[15] and mitochondrial DNA[16] sequences obtained from subfossil bones.[citation needed]

During the Pliocene, the Central American Isthmus formed, causing the Great American Interchange, and a mass extinction of much of the indigenous South American megafauna. Xenarthrans were largely unaffected and continued to thrive in spite of competition from the northern immigrants. Ground sloths were prominent among the various South American animal groups to migrate northwards into North America, where they remained and flourished until the late Pleistocene.[17]

The rhinoceros-sized Promegatherium of the Miocene is suggested to be the ancestor of Megatherium. The oldest (and smallest) species of Megatherium is M. altiplanicum of Pliocene Bolivia.[1] It was very similar to Promegatherium, and was also about the size of a rhinoceros. M. tarijense has been regarded as a medium-sized Megatherium species, larger than M. altiplanicum, but smaller than M. americanum. It roamed from the Tarija Basin in Bolivia to Yantac in Peru.[12] The oldest-known remains of Megatherium from the Pampas dates to the late Pliocene, around 3.58 million years ago.[18] Species of Megatherium became larger over time, with the largest species, M. americanum of the Late Pleistocene, reaching the size of an African elephant. The oldest records of M. americanum are from the latter half of the Middle Pleistocene, around 0.4 Ma (400 ka) ago.[19]

The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig. 4 of Presslee et al., 2019).[15]

  Folivora  

Megalocnidae† (Caribbean sloths)

  Nothrotheriidae  

Nothrotheriops shastensis†    

  Megatheriidae  

Megatherium americanum

Megatherioidea

Scelidotheriidae

Choloepodidae (two-fingered sloths)

Mylodontidae

Mylodontoidea

Description

 
 
Reconstruction of Megatherium with hair (top) and without (bottom).

Megatherium americanum was one of the largest animals in its habitat, weighing up to 3.8–4.58 t (8,400–10,100 lb),[20][21][22][23] with a shoulder height of 2.1 m (6 ft 11 in) and length of 6 m (20 ft) from head to tail.[24][25][26] It was one of the largest ground sloths, about as big as modern Asian elephants. Megatherium species were members of the abundant Pleistocene megafauna, large mammals that lived during the Pleistocene epoch.[citation needed]

Megatherium had a robust skeleton with a large pelvic girdle and a broad muscular tail. Its large size enabled it to feed at heights unreachable by other contemporary herbivores. Rising on its powerful hind legs and using its tail to form a tripod, Megatherium could support its massive body weight while using the curved claws on its long forelegs to pull down branches with the choicest leaves. This sloth, like a modern anteater, walked on the sides of its feet because its claws prevented it from putting them flat on the ground. Although it was primarily a quadruped, its trackways show that it was capable of bipedal locomotion. Biomechanical analysis also suggests it had adaptations to bipedalism.[22]

One study has proposed that Megatherium was mostly hairless, like modern elephants, because its large size and small surface-area-to-volume ratio would have made it susceptible to overheating.[27]

Mouth

Megatherium had a narrow, cone-shaped mouth and prehensile lips that were probably used to select particular plants and fruits.[28] Megatherium also possessed the narrowest muzzle of all ground sloths from the Pleistocene, possibly meaning it was a very selective eater, able to carefully pick and choose which leaves and twigs to consume.[28] While some evidence suggests the animal could use its tongue to differentiate and select its foliage, the lips probably had a more important role in this.[29] In Megatherium, the stylohyal and epihyal bones (parts of the hyoid bone which supports the tongue and is located in the throat) were fused together, and the apparatus lies farther upwards the throat, which, together with the elongated, steeply inclined mandibular symphysis, indicates a relatively shorter geniohyoid muscle and thus more limited capacity for tongue protrusion.[30] Analysis of wear and the biomechanics of the chewing muscles suggests that they chewed vertically. Megatheres displayed deeper jaws than other sloths.[20]

Like other sloths, Megatherium lacked the enamel, deciduous dentition and dental cusp patterns of other mammals. Instead of enamel, the tooth displays a layer of cementum, orthodentine and modified orthodentine, creating a soft, easily abraded surface.[29] The teeth of M. americanum exhibit extreme hypsodonty, indicative of its gritty, fibrous diet. Their teeth in side view show interlocking V-shaped biting surfaces, although they are nearly square in cross-section and exhibit bilophodonty. The teeth are spaced equidistantly in a series, located in the back of the mouth, which leaves space at the predentary, but with no diastema, although the length of this tooth row and of the predentary spout can vary by species.[clarification needed][20]

Habitat

 
M. americanum restoration

Megatherium inhabited woodland and grassland environments of the lightly wooded areas of South America, with a Late Pleistocene range centred around the Pampas[31] where it was an endemic species, as recently as 10,000 years ago. Megatherium was adapted to temperate, arid or semiarid open habitats. An example of these most recent finds is at Cueva del Milodón in Patagonian Chile.[32] The closely related genus Eremotherium (that has been classified occasionally as part of Megatherium)[33] lived in more tropical environments further north, and invaded temperate North America as part of the Great American Interchange.

Paleobiology

 
Restoration of M. americanum by Robert Bruce Horsfall, 1913

The giant ground sloth lived mostly in groups, but it may have lived singly in caves. It probably had mainly a browsing diet in open habitats, but also it probably fed on other moderate to soft tough food. For millions of years, the sloth did not have many enemies to bother it, so it was probably a diurnal animal.[citation needed]

The giant ground sloth was a herbivore, feeding on leaves such as yuccas, agaves and grasses.[citation needed] While it fed chiefly on terrestrial plants, it could also stand on its hind legs, using its tail as a balancing tripod, and reach for upper growth vegetation. It would pull itself upright to sit on its haunches or to stand and then tugged at plants with its feet, digging them up with the five sharp claws on each foot. The sloth used its simple teeth to grind down food before swallowing it, and its highly developed cheek muscles helped in this process. The sloth's stomach was able to digest coarse and fibrous food.[citation needed] It is likely that it spent a lot of time resting to aid digestion.

 
M. americanum skull
 
Claw of Megatherium

A recent morpho-functional analysis[20] indicates that M. americanum was adapted for strong vertical biting. The teeth are hypsodont and bilophodont, and the sagittal section of each loph is triangular with a sharp edge. This suggests that the teeth were used for cutting, rather than grinding, and that hard fibrous food was not the primary dietary component.

While it has been suggested that the giant sloth may have been partly carnivorous, this is a controversial claim. Richard Fariña and Ernesto Blanco of the Universidad de la República in Montevideo have analysed a fossil skeleton of M. americanum and discovered that its olecranon—the part of the elbow to which the triceps muscle attaches—was very short. This adaptation is found in carnivores and optimises speed rather than strength. The researchers say this would have enabled M. americanum to use its claws like daggers. They suggest that to add nutrients to its diet, Megatherium may have taken over the kills of Smilodon. Based on the estimated strength and mechanical advantage of its biceps, it has been proposed that Megatherium could have overturned adult glyptodonts (large, armored xenarthrans, related to armadillos) as a means of scavenging or hunting these animals.[34] However, noting that sloths lack the carnassials typical of predators and that traces of bone are absent from the many preserved deposits of sloth dung, Paul Martin has described this proposal as "fanciful".[A] Carbon isotope analysis has found that Megatherium has isotope values similar to other megafaunal herbivores such as mammoths, glyptodonts and Macrauchenia, and significantly unlike omnivorous and carnivorous mammals, suggesting that Megatherium was an obligate herbivore.[35]

Extinction

 
M. americanum sculpture in Crystal Palace Park

The youngest unambiguous dates for Megatherium are from the end of the Late Pleistocene. Supposed early Holocene dates obtained for Megatherium and other Pampas megafauna have been questioned, with suggestions that they are likely due to humic acid contamination of the collagen used to radiocarbon date the bones.[4] Megatherium disappeared simultaneously along with the vast majoriy (>80%) of other large (megafaunal) South American mammals, as part of the Quaternary extinction event.[36] The use of bioclimatic envelope modeling indicates that the area of suitable habitat for Megatherium had shrunk and become fragmented by the mid-Holocene. While this alone would not likely have caused its extinction, it has been cited as a possible contributing factor.[37]

Towards the end of the Late Pleistocene, humans first arrived in the Americas, with some of the earliest evidence of humans in South America being the Monte Verde II site in Chile, dating to around 14,500 years Before Present ~(12,500 BC).[38] The extinction interval of Megatherium and other megafauna coincides with the appearance and abundance of Fishtail projectile points, which are suggested to have been used to hunt megafauna, across the Pampas region and South America more broadly.[39] There is evidence for the butchery of Megatherium by humans. Two M. americanum bones, an ulna[40] and an atlas vertebra,[41] from separate collections, bear cut marks suggestive of butchery, with the latter suggested to represent an attempt to exploit the contents of the head.[41] A kill site dating to around 12,600 years Before Present (BP), is known from Campo Laborde in the Pampas in Argentina, where a single individual of M. americanum was slaughtered and butchered, which is the only confirmed giant ground-sloth kill site in the Americas. At the site several stone tools were present, including the fragment of a projectile point.[4] Another possible kill site is Arroyo Seco 2 near Tres Arroyos in the Pampas in Argentina, where M. americanum bones amongst those of other megafauna were found associated with humans artifacts dating to approximately 14,782–11,142 cal yr BP.[42] This hunting may have been a factor in its extinction.[39]

Cultural references

The Megatherium Club, named for the extinct animal and founded by William Stimpson, was a group of Washington, D.C.-based scientists who were attracted to that city by the Smithsonian Institution's rapidly growing collection, from 1857 to 1866.

Notes

  1. ^ Martin (2005), p. 35

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External links

megatherium, often, misspelt, bacterium, bacillus, megaterium, ɪər, theer, from, greek, méga, μέγα, great, theríon, θηρίον, beast, extinct, genus, ground, sloths, endemic, south, america, that, lived, from, early, pliocene, through, pleistocene, best, known, e. For the often misspelt bacterium see Bacillus megaterium Megatherium m ɛ ɡ e ˈ 8 ɪer i e m meg e THEER ee em from Greek mega mega great therion 8hrion beast is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene 1 through the end of the Pleistocene 2 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 MegatheriumTemporal range Early Pliocene 1 to Early Holocene 5 0 010 Ma PreꞒ Ꞓ O S D C P T J K Pg N Possible later date of 0 008 Ma M americanum skeleton Natural History Museum London Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Class Mammalia Order Pilosa Clade Megatheria Family Megatheriidae Subfamily Megatheriinae Genus MegatheriumCuvier 1796 Type species Megatherium americanumCuvier 1796 Subgenera Megatherium M altiplanicum Saint Andre amp De Iuliis 2001 M americanum Cuvier 1796 Pseudomegatherium M celendinense Pujos 2006 M medinae Philippi 1893 M sundti Philippi 1893 M tarijense Gervais amp Ameghino 1880 M urbiani Pujos amp Salas 2004 Map showing the distribution of all Megatherium species in red inferred from fossil finds Synonyms Essonodontherium Ameghino 1884 Orocanthus Ameghino 1885 Neoracanthus Ameghino 1889 Megatherium is part of the sloth family Megatheriidae which also includes the similarly giant Eremotherium comparable in size to M americanum which was native to tropical South America Central America and North America as far north as the southern United States Megatherium was first discovered in 1788 on the bank of the Lujan River in Argentina The holotype specimen was then shipped to Spain the following year wherein it caught the attention of the paleontologist Georges Cuvier who was the first to determine by means of comparative anatomy that Megatherium was a sloth 3 Megatherium became extinct around 12 000 years ago as part of the Late Pleistocene extinctions simultaneously with the majority of other large mammals in the Americas The extinctions followed the first arrival of humans in the Americas and one and potentially multiple kill sites where M americanum was slaughtered and butchered is known suggesting that hunting could have caused its extinction 4 Contents 1 Taxonomy 1 1 Evolution 2 Description 2 1 Mouth 3 Habitat 4 Paleobiology 5 Extinction 6 Cultural references 7 Notes 8 References 9 External linksTaxonomyMegatherium is divided into 2 subgenera Megatherium and Pseudomegatherium Taxonomy according to Pujos 2006 and De Iuliis et al 2009 5 6 Subgenus Megatherium M altiplanicum Saint Andre amp de Iuliis 2001 M americanum Cuvier 1796 Subgenus Pseudomegatherium Kraglievich 1931 M celendinense Pujos 2006 M medinae Philippi 1893 M sundti Philippi 1893 M tarijense Gervais amp Ameghino 1880 M urbinai Pujos amp Salas 2004 nbsp Specimen of M americanum in Museo Nacional de Ciencias Naturales Madrid the first prehistoric animal skeleton mounted in 1795 The first fossil specimen of Megatherium was discovered in 1788 by Manuel Torres on the bank of the Lujan River in Argentina The fossil was shipped to Museo Nacional de Ciencias Naturales in Madrid the following year where it remains It was reassembled by museum employee Juan Bautista Bru who also drew the skeleton and some individual bones 7 Based on Bru s illustrations comparative anatomist Georges Cuvier determined the relationships and appearance of Megatherium He published his first paper on the subject in 1796 8 a transcript of a previous lecture at the French Academy of Sciences He published on the subject again in 1804 this paper was republished in his book Recherches sur les ossemens fossiles de quadrupedes 3 8 In his 1796 paper Cuvier assigned the fossil the scientific name Megatherium americanum Cuvier determined that Megatherium was a sloth and at first believed that it used its large claws for climbing trees like modern sloths although he later changed his hypothesis to support a subterranean lifestyle with the claws used to dig tunnels 3 Fossils of Megatherium and other western megafauna proved popular with the Georgian era public preceding the discovery of giant dinosaurs some decades later Since the original discovery numerous other fossil Megatherium skeletons have been discovered across South America in Argentina Bolivia Brazil Chile Colombia Quipile Cundinamarca 9 10 Guyana Paraguay Peru and Uruguay 2 New species in the genus Megatherium M urbinai and M celendinense have been described in 2004 and 2006 respectively 11 M celedinense is named after Celendin Cajamarca Province in the Peruvian Andes 5 These species are considerably smaller than M americanum and are considered to belong to a separate subgenus Pseudomegatherium 5 The species Megatherium Pseudomegatherium tarijense appears to be a junior synonym of M americanum and merely a small individual 12 The species Megatherium filholi Moreno 1888 of the Pampas previously thought to be a junior synonym of M americanum representing juvenile individuals was suggested to be a distinct valid species in 2019 13 Megatherium gallardoi Ameghino amp Kraglievich 1921 from the Ensenadan of Argentina was suggested to be a valid species in 2008 most closely related to M americanum and M altiplanicum 14 M parodii Hoffstetter 1949 and M istilarti Kraglievich 1925 have not had their validity assessed in recent literature Evolution nbsp Bru s 1796 skeletal drawing of M americanum Ground sloths are a diverse group belonging to superorder Xenarthra which also includes extinct pampatheres and glyptodonts as well as living tree sloths anteaters and armadillos One of the four major eutherian radiations this superorder evolved in isolation in South America while it was an island continent during the Paleogene and Neogene The family to which Megatherium belongs Megatheriidae is related within superfamily Megatherioidea to the extinct families Nothrotheriidae and Megalonychidae and to living three toed sloths of family Bradypodidae as deduced recently from collagen 15 and mitochondrial DNA 16 sequences obtained from subfossil bones citation needed During the Pliocene the Central American Isthmus formed causing the Great American Interchange and a mass extinction of much of the indigenous South American megafauna Xenarthrans were largely unaffected and continued to thrive in spite of competition from the northern immigrants Ground sloths were prominent among the various South American animal groups to migrate northwards into North America where they remained and flourished until the late Pleistocene 17 The rhinoceros sized Promegatherium of the Miocene is suggested to be the ancestor of Megatherium The oldest and smallest species of Megatherium is M altiplanicum of Pliocene Bolivia 1 It was very similar to Promegatherium and was also about the size of a rhinoceros M tarijense has been regarded as a medium sized Megatherium species larger than M altiplanicum but smaller than M americanum It roamed from the Tarija Basin in Bolivia to Yantac in Peru 12 The oldest known remains of Megatherium from the Pampas dates to the late Pliocene around 3 58 million years ago 18 Species of Megatherium became larger over time with the largest species M americanum of the Late Pleistocene reaching the size of an African elephant The oldest records of M americanum are from the latter half of the Middle Pleistocene around 0 4 Ma 400 ka ago 19 The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data see Fig 4 of Presslee et al 2019 15 Folivora Megalocnidae Caribbean sloths Nothrotheriidae Nothrotheriops shastensis Megatheriidae Megatherium americanum Megalonychidae Megalonyx jeffersoni Bradypodidae three fingered sloths B torquatus B pygmaeus B tridactylus B variegatus Megatherioidea Scelidotheriidae Choloepodidae two fingered sloths Mylodontidae MylodontoideaDescription nbsp nbsp Reconstruction of Megatherium with hair top and without bottom Megatherium americanum was one of the largest animals in its habitat weighing up to 3 8 4 58 t 8 400 10 100 lb 20 21 22 23 with a shoulder height of 2 1 m 6 ft 11 in and length of 6 m 20 ft from head to tail 24 25 26 It was one of the largest ground sloths about as big as modern Asian elephants Megatherium species were members of the abundant Pleistocene megafauna large mammals that lived during the Pleistocene epoch citation needed Megatherium had a robust skeleton with a large pelvic girdle and a broad muscular tail Its large size enabled it to feed at heights unreachable by other contemporary herbivores Rising on its powerful hind legs and using its tail to form a tripod Megatherium could support its massive body weight while using the curved claws on its long forelegs to pull down branches with the choicest leaves This sloth like a modern anteater walked on the sides of its feet because its claws prevented it from putting them flat on the ground Although it was primarily a quadruped its trackways show that it was capable of bipedal locomotion Biomechanical analysis also suggests it had adaptations to bipedalism 22 One study has proposed that Megatherium was mostly hairless like modern elephants because its large size and small surface area to volume ratio would have made it susceptible to overheating 27 Mouth Megatherium had a narrow cone shaped mouth and prehensile lips that were probably used to select particular plants and fruits 28 Megatherium also possessed the narrowest muzzle of all ground sloths from the Pleistocene possibly meaning it was a very selective eater able to carefully pick and choose which leaves and twigs to consume 28 While some evidence suggests the animal could use its tongue to differentiate and select its foliage the lips probably had a more important role in this 29 In Megatherium the stylohyal and epihyal bones parts of the hyoid bone which supports the tongue and is located in the throat were fused together and the apparatus lies farther upwards the throat which together with the elongated steeply inclined mandibular symphysis indicates a relatively shorter geniohyoid muscle and thus more limited capacity for tongue protrusion 30 Analysis of wear and the biomechanics of the chewing muscles suggests that they chewed vertically Megatheres displayed deeper jaws than other sloths 20 Like other sloths Megatherium lacked the enamel deciduous dentition and dental cusp patterns of other mammals Instead of enamel the tooth displays a layer of cementum orthodentine and modified orthodentine creating a soft easily abraded surface 29 The teeth of M americanum exhibit extreme hypsodonty indicative of its gritty fibrous diet Their teeth in side view show interlocking V shaped biting surfaces although they are nearly square in cross section and exhibit bilophodonty The teeth are spaced equidistantly in a series located in the back of the mouth which leaves space at the predentary but with no diastema although the length of this tooth row and of the predentary spout can vary by species clarification needed 20 Habitat nbsp M americanum restoration Megatherium inhabited woodland and grassland environments of the lightly wooded areas of South America with a Late Pleistocene range centred around the Pampas 31 where it was an endemic species as recently as 10 000 years ago Megatherium was adapted to temperate arid or semiarid open habitats An example of these most recent finds is at Cueva del Milodon in Patagonian Chile 32 The closely related genus Eremotherium that has been classified occasionally as part of Megatherium 33 lived in more tropical environments further north and invaded temperate North America as part of the Great American Interchange Paleobiology nbsp Restoration of M americanum by Robert Bruce Horsfall 1913 The giant ground sloth lived mostly in groups but it may have lived singly in caves It probably had mainly a browsing diet in open habitats but also it probably fed on other moderate to soft tough food For millions of years the sloth did not have many enemies to bother it so it was probably a diurnal animal citation needed The giant ground sloth was a herbivore feeding on leaves such as yuccas agaves and grasses citation needed While it fed chiefly on terrestrial plants it could also stand on its hind legs using its tail as a balancing tripod and reach for upper growth vegetation It would pull itself upright to sit on its haunches or to stand and then tugged at plants with its feet digging them up with the five sharp claws on each foot The sloth used its simple teeth to grind down food before swallowing it and its highly developed cheek muscles helped in this process The sloth s stomach was able to digest coarse and fibrous food citation needed It is likely that it spent a lot of time resting to aid digestion nbsp M americanum skull nbsp Claw of Megatherium A recent morpho functional analysis 20 indicates that M americanum was adapted for strong vertical biting The teeth are hypsodont and bilophodont and the sagittal section of each loph is triangular with a sharp edge This suggests that the teeth were used for cutting rather than grinding and that hard fibrous food was not the primary dietary component While it has been suggested that the giant sloth may have been partly carnivorous this is a controversial claim Richard Farina and Ernesto Blanco of the Universidad de la Republica in Montevideo have analysed a fossil skeleton of M americanum and discovered that its olecranon the part of the elbow to which the triceps muscle attaches was very short This adaptation is found in carnivores and optimises speed rather than strength The researchers say this would have enabled M americanum to use its claws like daggers They suggest that to add nutrients to its diet Megatherium may have taken over the kills of Smilodon Based on the estimated strength and mechanical advantage of its biceps it has been proposed that Megatherium could have overturned adult glyptodonts large armored xenarthrans related to armadillos as a means of scavenging or hunting these animals 34 However noting that sloths lack the carnassials typical of predators and that traces of bone are absent from the many preserved deposits of sloth dung Paul Martin has described this proposal as fanciful A Carbon isotope analysis has found that Megatherium has isotope values similar to other megafaunal herbivores such as mammoths glyptodonts and Macrauchenia and significantly unlike omnivorous and carnivorous mammals suggesting that Megatherium was an obligate herbivore 35 Extinction nbsp M americanum sculpture in Crystal Palace Park The youngest unambiguous dates for Megatherium are from the end of the Late Pleistocene Supposed early Holocene dates obtained for Megatherium and other Pampas megafauna have been questioned with suggestions that they are likely due to humic acid contamination of the collagen used to radiocarbon date the bones 4 Megatherium disappeared simultaneously along with the vast majoriy gt 80 of other large megafaunal South American mammals as part of the Quaternary extinction event 36 The use of bioclimatic envelope modeling indicates that the area of suitable habitat for Megatherium had shrunk and become fragmented by the mid Holocene While this alone would not likely have caused its extinction it has been cited as a possible contributing factor 37 Towards the end of the Late Pleistocene humans first arrived in the Americas with some of the earliest evidence of humans in South America being the Monte Verde II site in Chile dating to around 14 500 years Before Present 12 500 BC 38 The extinction interval of Megatherium and other megafauna coincides with the appearance and abundance of Fishtail projectile points which are suggested to have been used to hunt megafauna across the Pampas region and South America more broadly 39 There is evidence for the butchery of Megatherium by humans Two M americanum bones an ulna 40 and an atlas vertebra 41 from separate collections bear cut marks suggestive of butchery with the latter suggested to represent an attempt to exploit the contents of the head 41 A kill site dating to around 12 600 years Before Present BP is known from Campo Laborde in the Pampas in Argentina where a single individual of M americanum was slaughtered and butchered which is the only confirmed giant ground sloth kill site in the Americas At the site several stone tools were present including the fragment of a projectile point 4 Another possible kill site is Arroyo Seco 2 near Tres Arroyos in the Pampas in Argentina where M americanum bones amongst those of other megafauna were found associated with humans artifacts dating to approximately 14 782 11 142 cal yr BP 42 This hunting may have been a factor in its extinction 39 Cultural referencesThe Megatherium Club named for the extinct animal and founded by William Stimpson was a group of Washington D C based scientists who were attracted to that city by the Smithsonian Institution s rapidly growing collection from 1857 to 1866 Notes Martin 2005 p 35References a b c Saint Andre P A De Iuliis G 2001 The smallest and most ancient representative of the genus Megatherium Cuvier 1796 Xenarthra Tardigrada Megatheriidae from the Pliocene of the Bolivian Altiplano PDF Geodiversitas 23 4 625 645 Archived from the original PDF on 2013 10 29 Retrieved 14 April 2016 a b Zurita A E Carlini A A Scillato Yane G J Tonni E P 2004 Mamiferos extintos del Cuaternario de la Provincia del Chaco Argentina y su relacion con aquellos del este de la region pampeana y de Chile Revista Geologica de Chile 31 1 65 87 doi 10 4067 S0716 02082004000100004 a b c Argot Christine 21 May 2008 Changing Views in Paleontology The Story of a Giant Megatherium Xenarthra In Sargis E J Dagosto M eds Mammalian Evolutionary Morphology A Tribute to Frederick S Szalay Springer pp 37 50 ISBN 978 1 4020 6997 0 OCLC 236490247 a b c Politis Gustavo G Messineo Pablo G Stafford Thomas W Lindsey Emily L March 2019 Campo Laborde A Late Pleistocene giant ground sloth kill and butchering site in the Pampas Science Advances 5 3 eaau4546 Bibcode 2019SciA 5 4546P doi 10 1126 sciadv aau4546 ISSN 2375 2548 PMC 6402857 PMID 30854426 a b c Pujos Francois 2006 Megatherium celendinense sp nov from the Pleistocene of the Peruvian Andes and the phylogenetic relationships of Megatheriines Palaeontology 49 2 285 306 Bibcode 2006Palgy 49 285P doi 10 1111 j 1475 4983 2006 00522 x S2CID 84225654 De Iuliis Gerardo Pujos Francois Tito Giuseppe 2009 12 12 Systematic and taxonomic revision of the Pleistocene ground sloth Megatherium Pseudomegatherium tarijense Xenarthra Megatheriidae Journal of Vertebrate Paleontology 29 4 1244 1251 Bibcode 2009JVPal 29 1244D doi 10 1671 039 029 0426 ISSN 0272 4634 S2CID 84272333 Pinero J M L Spring 1988 Juan Bautista Bru 1740 1799 and the description of the genus Megatherium Journal of the History of Biology 21 1 147 163 doi 10 1007 BF00125797 S2CID 80631212 a b Babcock Loren E 2024 03 18 Nomenclatural history of Megalonyx Jefferson 1799 Mammalia Xenarthra Pilosa Megalonychidae ZooKeys 1195 297 308 doi 10 3897 zookeys 1195 117999 ISSN 1313 2970 PMC 10964019 PMID 38532771 Burgl Hans 1956 Restos de Megatherium y otros fosiles de Quipile Cundinamarca Ingeominas 1 14 Retrieved 2017 05 03 De Porta Jaime 1961 La posicion estratigrafica de la fauna de Mamiferos del pleistoceno de la Sabana de Bogota Boletin de Geologia Universidad Industrial de Santander 7 37 54 Retrieved 2017 05 03 Pujos Francois Salas Rodolfo 2004 A new species of Megatherium Mammalia Xenarthra Megatheriidae from the Pleistocene of Sacaco and Tres Ventanas Peru Palaeontology 47 3 579 604 Bibcode 2004Palgy 47 579P doi 10 1111 j 0031 0239 2004 00376 x a b De Iuliis G Pujos F Tito G 2009 Systematic and taxonomic revision of the Pleistocene ground sloth Megatherium Pseudomegatherium tarijense Xenarthra Megatheriidae Journal of Vertebrate Paleontology 29 4 1244 1251 Bibcode 2009JVPal 29 1244D doi 10 1671 039 029 0426 JSTOR 20627134 S2CID 84272333 Agnolin Federico L Chimento Nicolas R Brandoni Diego Boh Daniel Campo Denise H Magnussen Mariano De Cianni Francisco 2018 09 01 New Pleistocene remains of Megatherium filholi Moreno 1888 Mammalia Xenarthra from the Pampean Region Implications for the diversity of Megatheriinae of the Quaternary of South America Neues Jahrbuch fur Geologie und Palaontologie Abhandlungen 289 3 339 348 doi 10 1127 njgpa 2018 0777 ISSN 0077 7749 S2CID 134660849 Brandoni Diego Soibelzon Esteban Scarano Alejo Carlos December 2008 On Megatherium gallardoi Mammalia Xenarthra Megatheriidae and the Megatheriinae from the Ensenadan lower to middle Pleistocene of the Pampean region Argentina Geodiversitas ISSN 1280 9659 a b Presslee S Slater G J Pujos F Forasiepi A M Fischer R Molloy K Mackie M Olsen J V Kramarz A Taglioretti M Scaglia F Lezcano M Lanata J L Southon J Feranec R Bloch J Hajduk A Martin F M Gismondi R S Reguero M de Muizon C Greenwood A Chait B T Penkman K Collins M MacPhee R D E 2019 Palaeoproteomics resolves sloth relationships PDF Nature Ecology amp Evolution 3 7 1121 1130 Bibcode 2019NatEE 3 1121P doi 10 1038 s41559 019 0909 z PMID 31171860 S2CID 174813630 Archived PDF from the original on 2022 10 09 Delsuc F Kuch M Gibb G C Karpinski E Hackenberger D Szpak P Martinez J G Mead J I McDonald H G MacPhee R D E Billet G Hautier L Poinar H N 2019 Ancient Mitogenomes Reveal the Evolutionary History and Biogeography of Sloths Current Biology 29 12 2031 2042 e6 Bibcode 2019CBio 29E2031D doi 10 1016 j cub 2019 05 043 PMID 31178321 Martin P S 2005 Twilight of the Mammoths Ice Age Extinctions and the Rewilding of America Illustrated ed University of California Press ISBN 978 0520231412 OCLC 58055404 Retrieved 2014 09 11 Chimento Nicolas R 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stabber Proceedings of the Royal Society of London 263 1377 1725 1729 doi 10 1098 rspb 1996 0252 PMID 9025315 S2CID 9451444 Bocherens H Cotte M Bonini R A Straccia P Scian D Soibelzon L Prevosti F J August 2017 Isotopic insight on paleodiet of extinct Pleistocene megafaunal Xenarthrans from Argentina Gondwana Research 48 7 14 Bibcode 2017GondR 48 7B doi 10 1016 j gr 2017 04 003 Anthony D Barnosky Paul L Koch Robert S Feranec Scott L Wing Alan B Shabel 2004 Assessing the Causes of Late Pleistocene Extinctions on the Continents Science 306 5693 70 75 Bibcode 2004Sci 306 70B CiteSeerX 10 1 1 574 332 doi 10 1126 science 1101476 PMID 15459379 S2CID 36156087 Lima Ribeiro Matheus Souza et al December 2012 Potential Suitable Areas of Giant Ground Sloths Dropped Before its Extinction in South America the Evidences from Bioclimatic Envelope Modeling Natureza amp Conservacao 10 2 145 151 doi 10 4322 natcon 2012 022 Dillehay Tom D Pino Mario Ocampo Carlos 2021 01 02 Comments on Archaeological Remains at the Monte Verde Site Complex Chile PaleoAmerica 7 1 8 13 doi 10 1080 20555563 2020 1762399 ISSN 2055 5563 S2CID 224935851 a b Prates Luciano Perez S Ivan 2021 04 12 Late Pleistocene South American megafaunal extinctions associated with rise of Fishtail points and human population Nature Communications 12 1 2175 Bibcode 2021NatCo 12 2175P doi 10 1038 s41467 021 22506 4 ISSN 2041 1723 PMC 8041891 PMID 33846353 Chichkoyan Karina V Martinez Navarro Bienvenido Moigne Anne Marie Belinchon Margarita Lanata Jose L June 2017 The exploitation of megafauna during the earliest peopling of the Americas An examination of nineteenth century fossil collections Comptes Rendus Palevol 16 4 440 451 Bibcode 2017CRPal 16 440C doi 10 1016 j crpv 2016 11 003 a b Autoecologia Humana del Quaternari Departament d Historia i Historia de l Art Universitat Rovira i Virgili Martinez Navarro B Chichkoyan K V Moigne A M Cioppi E Belinchon M Lanata J L 2017 Description and interpretation of a Megatherium americanum atlas with evidence of human intervention Rivista Italiana di Paleontologia e Stratigrafia OCLC 1084743779 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link Bampi Hugo Barberi Maira Lima Ribeiro Matheus S December 2022 Megafauna kill sites in South America A critical review Quaternary Science Reviews 298 107851 Bibcode 2022QSRv 29807851B doi 10 1016 j quascirev 2022 107851 S2CID 253876769 External links nbsp Wikimedia Commons has media related to Megatherium BBC Walking With Beasts Megatherium London Review of Books Bare Bones Steven Shapin Megatherium Encyclopaedia Britannica 11th ed 1911 Retrieved from https en wikipedia org w index php title Megatherium amp oldid 1219695873, wikipedia, wiki, book, books, library,

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