Craniofacial variation of the Chinese macaques explored with Morphologika

In order to analyze, separately and dynamically, the variation in cranial size and shape of Chinese macaques, a new method, Morphologika, was used to illustrate 3D profiles based on the coordinates of 26 landmarks on the skull. Striking image variation between the two sexes was detected on the facial region: males exhibited a larger and more protrusive facial structure. Males also displayed a bigger cranium than females. The two sexes also showed quite different images in skull shape. However, they expressed the same allometric pattern with regard to the relationship between size and shape, which was significantly positively associated with each other along the first axis. The same relationship was negatively displayed along the second axis when the two sexes were analyzed together. However, only the relationship for females reached a significant level when the two sexes were studied separately. This was considered to be related to their differentiation in growth trajectory. This study also tested the concept of size revealed by the second axis of principal components analysis based on traditional morphometric methods on the same taxa.