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Megatheriinae were a group of elephant-sized ground sloths that lived from 2 million to 8,000 years ago. Their smaller ground sloth cousins were the Mylodon.
Characteristics
Unlike its living relative, the tree sloth, Megatherium was one of the largest mammals to walk the Earth. Weighing almost as much as an african bull elephant, it had huge claws on its feet. These claws meant that it could not put its feet flat on the ground and so, like a modern anteater, it had to walk on the sides of its feet. Its footprints show that it walked mainly on its hind legs. When it stood on its hind legs, it was about twice the height of an elephant, or about twenty feet tall.
The Megatherium had a robust skeleton with a large pelvic girdle and a broad muscular tail. Its large size and specially adapted body made it possible to feed at heights otherwise unobtainable to other contemporary herbivores. Rising on its powerful hind legs and using its tail to form a tripod, the Megatherium was able to support its massive body weight while using its long forelegs with curved claws to pull down branches with the choicest leaves. Its large deep jaw is believed to have housed a long tongue, as in the modern tree sloth, which it would then use to pull leaves into its mouth.
Some recent morpho-functional analysis (Bargo, 2001) indicate that M. americanum was well adapted for strong and mainly vertical biting. The teeth are extremely hypsodont and bilophodont, and the sagittal section of each loph is triangular with a sharp edge. This suggests that the teeth were used mainly for cutting, rather than grinding, and that hard and fibrous food was not the main dietary component.
There is a common misbelief that the sabre-toothed cat Smilodon hunted Megatherium, but the sloths were too big for even this large cat to attack. 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 aggressively, like daggers (Fariña and Blanco, 1996). The conclusion is that due to its nutrient-poor habitats, Megatherium may have actually taken over the kills of Smilodon.
Distribution
It was formerly thought that Megatherium lived only in South America. However, a University of Florida research team recently found a skeleton in North America. This was a new species of giant sloth, which weighed nearly as much as an African bull elephant, more than 5 tons. Unlike previous discovered species, it had 6 claws instead of 5.
Megatheriinae in Popular Fiction
Sid the Sloth from Ice Age and The Meltdown is some species of giant sloth.
In The Simpsons episode Treehouse of Horror V, in the time of the dinosaurs, Homer sees, very anachronistically, a large ground sloth, which makes a grunting noise not unlike a 'i dunno' sound and shrugs a shoulder when Homer asks a question to himself about whether or not his killing a giant mosquito will change the space-time continum.
In the episode "Tick vs. Prehistory" from the animated TV series The Tick a giant sloth appears, picking up the Tick's sidekick, Arthur.
References
External links
Prehistoric xenarthrans | Pleistocene mammals | Recent extinctions
Megatherium | עצלן קרקע ענק | Megatherium | メガテリウム | Megatherium
"Megatherium"