Giant Ground Sloth Scapula
Age: 50,000 - 30,000 Years Old / 1 Million Years Old
Pleistocene Epoch
Species: Paramylodon Harlain
Specimen: Vertebare
Discovered: Florida - Leisey Fossil Pit
Measures: 10" Long / 7.5" Wide (From longest lengths)
Weighs: 4.8lbs
 Info Card Included
 
Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Caribbean ground sloths, the most recent survivors, lived in the Antilles, possibly until 1550 BCE. However, radiocarbon dating suggests an age of between 2819 and 2660 BCE for the last occurrence of Megalocnus in Cuba. Ground sloths had been extinct on the mainland of North and South America for 10,000 years or more. They survived 5,000–6,000 years longer in the Caribbean than on the American mainland, which correlates with the later colonization of this area by humans.
 
Much ground sloth evolution took place during the late Paleogene and Neogene of South America, while the continent was isolated. At their earliest appearance in the fossil record, the ground sloths were already distinct at the family level. The presence of intervening islands between the American continents in the Miocene allowed a dispersal of forms into North America. A number of mid- to small-sized forms are believed to have previously dispersed to the Antilles. They were hardy as evidenced by their diverse numbers and dispersals into remote areas given the finding of their remains in Patagonia (Cueva del Milodón Natural Monument) and parts of Alaska.
 
Sloths, and xenarthrans as a whole, represent one of the more successful South American groups during the Great American Interchange. During the interchange, many more taxa moved from North America into South America than in the other direction. At least five genera of ground sloths have been identified in North American fossils; these are examples of successful immigration to the north.
 
Radiocarbon dating places the disappearance of ground sloths in what is now the United States at around 11,000 years ago. The Shasta ground sloth (Nothrotheriops shastensis) visited Rampart Cave (located on the Arizona side of the Lake Mead National Recreation Area) seasonally, leaving behind a massive stratified subfossilized dung deposit, and seemed to be flourishing from 13,000 until 11,000 BP, when the deposition suddenly stopped. Steadman et al. argue that it is no coincidence that studies have shown that ground sloths disappeared from an area a few years after the arrival of humans. Trackways preserved in New Mexico (probably dating from 10 to 15.6 thousand years ago) that appear to show a group of humans chasing or harassing three Nothrotheriops or Paramylodon ground sloths may record the scene of a hunt. The tracks are interpreted as showing seven instances of a sloth turning and rearing up on its hind legs to confront its pursuers, while the humans approach from multiple directions, possibly in an attempt to distract it.
 
Those who argue in favor of humans being the direct cause of the ground sloths' extinction point out that the few sloths that remain are small sloths that spend most of their time in trees, making it difficult for them to be spotted. Although these sloths were well hidden, they still would have been affected by the climate changes that others claim wiped out the ground sloths. Additionally, after the continental ground sloths disappeared, insular sloths of the Caribbean survived for approximately 6,000 years longer, which correlates with the fact that these islands were not colonized by humans until about 5500 yr BP.
 
It is difficult to find evidence that supports either claim on whether humans hunted the ground sloths to extinction. Removing large amounts of meat from large mammals such as the ground sloth requires no contact with the bones; tool-inflicted damage to bones is a key sign of human interaction with the animal.