MORPHOLOGICAL ADAPTATION TO DIET IN PLATYRRHINE PRIMATES

Morphological features of the jaws and teeth are examined in eight spe cies of platyrrhine monkeys that coexist in the Suriname rainforest. Z -scores calculated from geometric predictions for several features of the feeding apparatus thought to have some functional significance (e. g., tooth dimensions, jaw robusticity, leverage of primary jaw elevato rs) are compared to a profile of the naturalistic dietary behavior of these species (i.e., proportions of fruit mesocarp, seeds, leaves, and fauna eaten). Several features are found exclusively in those platyrr hines whose dietary preferences are the most limited. Such specializat ions appear to be associated with a particular protein source exploite d by a species to supplement a largely frugivorous diet. Ateles panisc us, which feeds primarily on the mesocarp of ripe fruit, has an adapti ve morphology that emphasizes broad incisors. Chiropotes satanas (and to a slightly lesser extent, Pithecia pithecia) is a frugivore/ seed p redator with large upper and lower canines and a robust mandible. The frugivore/folivore Alouatta seniculus has a relatively large total mol ar area and effective mandibular condyle height. In all four of these strictly vegetarian species, the leverage of the masseter muscle is gr eater than that of temporalis. Of the omnivorous species, Cebus apella and C. nigrivittatus exploit both fauna and seeds for protein and exh ibit an array of many of the above features, such as large teeth and t hick mandibles. Saimiri sciureus, not particularly known for seed pred ation, departs from Cebus in having less robust canines and a more gra cile mandible. All three cebid omnivores have a temporalis with greate r leverage than the masseter, indicating a requirement for resisting a nteriorly directed forces, for example, using the jaws for vigorous fo raging. The lack of any enlarged features, other than incisors, in the omnivorous Saguinus midas may be attributable to the functional const raints of small body size. Because the small size of the gape limits t he size of the food parcel ingested, a requirement to enlarge other de ntomandibular structures for trituration is alleviated. (C) 1994 Wiley -Liss, Inc.