Doctoral Dissertation Improvement: Dental Microstructure and Growth in the Cebidae

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Teeth are obviously important in feeding and vital to discovering crucial ecological information about extinct species, including our own prehistoric ancestors. They also embed environmentally related forensic information. Teeth grow in a periodic, incremental manner similar to the way tree rings grow, and thus preserve a permanent record of their own formation. They develop along a time schedule that is coordinated adaptatively with events like weaning, with the nature of non-maternal food resources, and even the maturation of an individual as he/she develops their own species-specific social roles. Ongoing research aims to delineate this type of information from teeth among several primate groups, but major gaps remain. This project is the first to focus on dental microanatomy and growth in New World primates, specifically the capuchins, squirrel monkeys, tamarins, and marmosets. As an example where this work addresses new issues of wide significance, it is not known if seasonal dietary fluctuations impact overall bodily growth rates of a given species. Such information is hard to come by, even when monitoring animals in the wild. However, the approach of this study can reveal if incidental lean periods, as occurs during the dry season for many rain forest species, influences growth rates of teeth, which mirrors overall body growth. As another instance, although it is common for male primates to have larger canine teeth than females when living under certain social and mating systems, we understand little about how canine tooth size differences develop, meaning our understanding of the pervasive phenomenon of sexual dimorphism is rather incomplete. In a more general vein, most research in this field has concentrated on broadly surveying differences among families of primates, or higher taxonomic levels. Thus we know little about dental growth and its patterns at the species and genus level, or within an adaptive radiation. By focusing on several species and genera of the platyrrhine primates this study promises to fill some of these gaps. Taxonomically, this group presents several advantages. They are arguably the largest and most diverse group of living primates but they have also been largely ignored in favor of their Old World cousins, such as macaques, baboons and apes. The animals chosen for this study (Family Cebidae) are a good place to start because they are dietetically diverse, with some species showing seasonal shifts in their diet. My pilot work has also revealed that some male cebids exhibit a pattern of canine growth that differs from Old World monkey models, suggesting that the platyrrhine monkeys may be more pertinent to reconstructing the early evolution of canines and social systems in higher primates. This project is to assist graduate student training. Some of the techniques that are being employed are new and, once proven, will enable researchers with various interests to take greater advantage of museum collections, including fossils, by allowing microanatomical information to be obtained without cutting teeth apart to expose their internal structure. The image databases that will be developed will be made publicly available on the web. All in all, the research will add a new aspect to our understanding of primate diversity and evolution.