A Comparison of the Masticatory Apparatus Among Rhinopithecus bieti,Macaca thibetana and M.m.lasiota

This paper dealt with the comparative study on the morphological features of masticatory apparatus.48 variables were measured from 40 skulla in four groups,Rhinopithecus bieti,Macaca mulatta lasiota,and adult and juvenile Macaca thibetana.All the variables and some combinations of them were exploited to study the relationships among behaviour,function and morphology etc.The results of clustering analysis show that thirteen index-like variables can separate golden monkeys from macaques,but the juvenile Macaca thibetana is quite different from all the adult groups.In Rhinopithecus bieti,the right side of the dental arch is larger than the left,and in adult macaques the left larger,in juvenile macaques,the right larger.However,there is not a significant difference between the left and the right side of the dental arches in any of the 4 groups.The decreasing sequence of symmetry index is from the adult Macaca thibetana to Rhinopithecus bieti,Macaca mulatta lasiota and juvenile Macaca thibetana.A regression reveals that nearly 70% of the variables significantly related to the skull weight.Sn ANOVA suggests that adult groups differ from one another above a significant level.And a Duncan multiple comparison shows that:11 variables between Macaca mulatta lasiota and Rhinopithecus bieti,12 between R.bieti and M.thibetana,12 between M.m.lasiota and M.thibetana are different above a significant level.It follows the sequences that (1) Macaca thibetana>(2) Macaca mulatta lasiota>(3)Rhinopithecus bieti>(4)juvenile Macaca thibetana in respect of masticatory force,and (3)>(2)>(1)>(4) in respect of mandibular robust.Rhinopithecus bieti use the force the most efficiently for mastication.From all of these,we find (3)>(1)>(2)>(4) in respect of masticatory capacity.All the morphological data mentioned above result in that the four groups have different diets from each other,especially between golden monkeys and macaques.This coincides with the field observation data on diets.Such results indicate that there is strong relationship between the diet and the morphology of the mandibles,and that to deduce the paleoenvironment from the morphology of the masticatory apparatus may be possible.