Arch form, tooth size, and occlusomandibular kinesis in the Ceboidea

Correlations between dental morphology, arch configuration, and jaw movement patterns were quantitatively investigated in 23 ceboid species to elucidate integrative aspects of occlusal functional anatomy in an adaptive and evolutionary context. Differential maxillary-mandibular arch widths are primary in guiding lateral jaw movements. These movements are characterized according to their associated condylar shifts as either predominantly translatory or rotational. Predominantly translatory movements result from peripheral contact relationships between maxillary arches which are considerably wider posteriorly than their opposing mandibular arches. The greatest degree of mandibular movement is in the molar region in functional association with wide "primitive" maxillary molars, narrow mandibular molars, constricted maxillary intercanine widths, and narrow maxillary incisors. In contrast, predominantly rotational masticatory jaw movements results from differential arch widths which are greatest in the maxillary canine and incisor regions. Here most jaw movement is in the anterior segment and this is reflected in small maxillary-mandibular molar widths differences, a high degree of premolarization, wide-set maxillary canine teeth, and wide maxillary incisors. Possible selectional factors in the putative evolution of rotational predominance in mastication from the more primitive translatory pattern are discussed.