Another candidate.
Megatheriumhttp://en.wikipedia.org/wiki/MegatheriumTake a look at this skeleton!
Megatherium was one of the largest mammals to walk the Earth, weighing five tons, about as much as an African bull elephant. When it stood on its hind legs, it was about twice the height of an elephant.
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. Its jaw is believed to have housed a long tongue, which it would then use to pull leaves into its mouth, similar to the modern tree sloth.
Some recent morpho-functional analysis[1] indicates that M. americanum was adapted for strong vertical biting.
Little is known about the giant ground sloth. It may have used its size and strength to take over the kills of Smilodon and to scavenge or hunt Glyptodon.
It was a herbivorous animal and, although it could stand on its hind legs, using its tail as a balancing tripod, to reach for vegetation, the giant ground sloth fed chiefly on terrestrial plants.
It is thought that the giant sloth lived in groups, but it may have lived singly in caves. It is also believed that it lived in woodland and grassland environments.