Acratocnus


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

Classification

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.

Location

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 small size and their large hooked claws.

Size

The various species of Acratocnus ranged in weight from, and were thus much larger than living tree sloths, which do not exceed.

Extinction

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 of their extinctions may have been climatic changes, or more likely, human hunting.