FEEDING AND DIET OF THE PLEISTOCENE GROUND SLOTH NEOCNUS (MAMMALIA: PILOSA: MEGALONYCHIDAE) FROM HAITI

Among the various genera of fossil sloth taxa recovered from the major Caribbean islands, Neocnus has the greatest diversity in terms of species number and distribution, with three species (N. comes, N. dousman, and N. toupiti) hailing from Hispaniola (Haiti and Dominican Republic). Recent discovery of jugal elements assignable to this genus have allowed not only the first description of this feature in Haitian Neocnus specimens but also enabled studies into the masticatory abilities of this sloth. Reconstruction of the prime masticatory muscles were used in conjunction with a geometric model to estimate relative bite force in specimens of Neocnus, as well as the extant tree sloths Bradypus and Choloepus, as a means of investigating chewing and feeding habits in the extinct taxon. In terms of structural morphology and muscle orientation, Neocnus more closely resembles the patterns exhibited by Bradypus by having an elevated mandibular condyle, greater expansion of the pterygoids, robust angular processes, and overall higher estimated values of bite force. This is in contrast to the close phylogenetic relation between Neocnus and Choloepus, although the shapes of the mandibular condyles and glenoid fossae are similar so as to permit differential occlusion of caniniforms versus molariforms in both taxa. Given the structural feeding morphology and the relative high bite force values, Neocnus utilized a masticatory grinding cycle with mesiodistal and labiolingual movements, and which emphasized strong versus fast closing components. Overall, Neocnus is interpreted as being a folivorous feeder on older, tougher vegetation, like Bradypus, but with the ability to be more selective in its food preferences for potentially younger leaves or softer fruits/foods.