Wear facets and cusp cavitations on the maxillary first molars in platyrrhine primates were observed based on functional aspects of dental wear. 411 specimens from all platyrrhine genera and Tarsius were examined by SEM concerning cusp cavitation, wear facet production, microwear as indicator of functional feature, included angle of Phase I and II, and the relative length of Phase I.
In Callitrichidae, cusps show a greater influence by puncture-crushing than by chewing. Buccal shearing and lingual crushing are emphasized, however, grinding is not developed except in Callithrix and Callimico. In Saimiri, less puncture-crushing than in callitrichid genera, buccal shearing and bucco-lingual crushing are developed. Grinding facet is formed in parallel with tooth wear. In Aotus and Callicebus, functional contrasts are shown as followings; Aotus is emphasized in crushing and grinding, whereas Callicebus is insisted in puncture-crushing, shearing and crushing. In Cebus, puncture-crushing represented the lightest of all. Specific function is not too much emphasized to absorb the others. All the facets are developed well and expressed by heavy crushing feature. In Ateles and Lagothrix, the state of cusp cavitation is not severe, although excavated rate is high. Buccal shearing is not developed and lingual grinding is extremely emphasized. The functionally specialized division between buccal and lingual sides is observed. In Brachyteles and Alouatta, heavy puncture-crushing, buccal shearing and lingual grinding are emphasized. The condition of these genera is thought as functional inconsistency. In Pitheciinae, puncture-crushing and Phase I facets are hardly existed, however, grinding is emphasized extremely. No occlusal area seem to act by high occlusal pressure.
Based on these results, primitive features in Saimiri are defined, then the functional relationships of molars among platyrrhine genera are discussed referring their foods and adaptive zones.
