A PRINCIPLE COMPONENTS ANALYSIS OF CRANIAL AND MANDIBULAR DATA FROM EXTINCT HOLOCENE SLOTHS FROM HAITI

Multiple genera and species of extinct sloths from Haiti have been recognized. However, some questions remain regarding the validity of those taxonomic groupings. The purpose of the present study is to examine morphological disparity among these taxa using skull and mandible measurements and principal components analyses, to test for their congruence with the current taxonomic arrangement. Skull and mandible measurements were taken from 75 different specimens of Acratocnus ye, Parocnus serus, Neocnus comes, Neocnus dousman, and Neocnus toupiti. Measurements were based on those used in previous morphometric studies of other extinct sloths. Of the 75 specimens, several were incomplete and very few of the skulls had matching mandibles. Therefore, the data were modified such that the final, most complete data set comprised 25 skulls and 29 mandibles. Separate principal components analyses were completed for the skull and the mandible. The PCA of the skull measurements revealed three distinct groups of data points representing the previously recognized genera Parocnus, Acratocnus, and Neocnus. Mandibular data did not show a separation between Acratocnus and Neocnus, though Parocnus was still separate. Based on these analyses, the distinctiveness of the genus Parocnus is strongly supported by both cranial and mandibular data, whereas only the cranial data supports the separation of Acratocnus from Neocnus. There is a strong overlap among the three species of Neocnus in both data sets, so the validity of these as separate species may need to be reconsidered.