Mandibular morphometrics among macaques: The case ofmacaca thibetana

Recent field studies suggest that Macaca thibetana,a large endemic Chinese macaque, may be quite folivorous, distinguishing it from most other macaque species, which tend to be primarily frugivorous. To understand how this diet affects its masticatory system, we conducted a comparative morphometric study of mandibular dimensions. We took linear measurements from male and female mandibles of this species as well as four other macaques—M. fascicularis, M. nemestrina, M. arctoides,and M. assamensis—and four species of Presbytis—P. obscura, P. rubicunda, P. cristata,and P. phayrei—and subjected to them to a variety of analyses. Based on analyses of variances and discriminant analyses on each sex individually, the mandible of M. thibetanacorresponds to expected patterns for folivorous primates with respect to its wide condyles and thick corpora. However, the height of the corpus and symphysis are lower, and the anteroposterior length of the condyle is longer than predicted for a folivore. In addition to interpretations specifically relating to M. thibetana,we also discuss the functional morphology of the other species in light of what is published about their diets.