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Acratocnus facts for kids

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Temporal range: Late Pleistocene (Rancholabrean)
Scientific classification

Anthony 1916
Type species
Acratocnus odontrigonus
Anthony, 1916
  • A. antillensis Matthew 1931
  • A. odontrigonus Anthony 1916
  • A. ye MacPhee et al. 2000

Habanocnus Mayo, 1978

Acratocnus is an extinct genus of ground sloths that were found on Cuba, Hispaniola (today the Dominican Republic and Haiti), and Puerto Rico.


Like all of the Antillean sloths, Acratocnus was formerly thought on the basis of morphological evidence to be a member of the family Megalonychidae, which was also thought to include Choloepus, the two-toed tree sloths. Recent molecular evidence has clarified that Caribbean sloths represent a separate basal branch of the sloth radiation, now placed in the family Megalocnidae.


Fossils of Acratocnus were found on the islands of Puerto Rico, Cuba, and Hispaniola, 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.


The various species of Acratocnus ranged in weight from 50 to 150 pounds (23 to 68 kg), and were thus much larger than living tree sloths (genera Choloepus and Bradypus), which do not exceed 20 pounds (9.1 kg).


As with many sloth fossils, these species of sloth have not been radiometrically dated. It is suggested that the Puerto Rican and Hispaniolan 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 by the indigenous peoples of the Caribbean.

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