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Acratocnus spp.
Topic Started: Apr 30 2014, 02:18 AM (1,613 Views)
Scalesofanubis
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Acratocnus spp.

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Temporal range: Pleistocene to Holocene

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Xenarthra
Order: Pilosa
Family: Megalonychidae
Genus: †Acratocnus
Species:

  • A. odontrigonus Anthony 1916
  • A. antillensis Matthew 1931
  • A. ye MacPhee, White & Woods 2000


Acratocnus is an extinct genus of ground sloth found in Cuba, Hispaniola and Puerto Rico.

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Relations
Like all of the Antillean sloths, Acratocnus is a member of the family Megalonychidae, whose sole surviving genus is Choloepus, representing the two-toed tree sloths.

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Description
The various species of Acratocnus ranged in weight from 50 to 150 lbs (22 to 68 kg), and were thus much larger than living tree sloths (genera Choloepus and Bradypus), which do not exceed 20 lbs (about 9 kg).

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Range and Habitat
The species of Acratocnus were found on the islands of Puerto Rico, Cuba and Hispanola, where they inhabited the montane forests of the highlands. The Puerto Rican ground sloth, Acratocnus odontrigonus is known from several poorly documented cave excavations in northwestern Puerto Rico. The various species are regarded as being semi-arboreal because of their (relatively speaking) small size and their large hooked claws.

Size
The various species of Acratocnus ranged in weight from 50 to 150 lbs (22 to 68 kg), and were thus much larger than living tree sloths (genera Choloepus and Bradypus), which do not exceed 20 lbs (about 9 kg).

Extinction
As with many sloth fossils, these species of sloth have not been radiometrically dated. It is suggested that the Puerto Rican and Hispanolan Acratocnus species survived into the late Pleistocene but disappeared by the mid-Holocene. The related Cuban ground sloth, Megalocnus rodens, survived until at least c. 6600 BP, and the latest survival reported for any of the Antillean sloths is c. 5000 BP, for the Hispaniolan Neocnus comes, based on AMS radiocarbon dating. The cause(s) of their extinctions may have been climatic changes, or more likely, human hunting.

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Edited by Taipan, Apr 30 2014, 10:55 PM.
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Taipan
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Steadman, D. W.; Martin, P. S.; MacPhee, R. D. E.; Jull, A. J. T.; McDonald, H. G.; Woods, C. A.; Iturralde-Vinent, M.; Hodgins, G. W. L. (2005-08-16). "Asynchronous extinction of late Quaternary sloths on continents and islands". Proc. Natl. Acad. Sci. USA (National Academy of Sciences) 102 (33): 11763–11768. doi:10.1073/pnas.0502777102.

Abstract
Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their “last appearance” datum at ≈11,000 radiocarbon years before present (yr BP) or slightly less in North America, ≈10,500 yr BP in South America, and ≈4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial–interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people.

http://www.pnas.org/content/102/33/11763.abstract
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