Enamel structure in primates: a review of scanning electron microscope studies

Comparative studies of dental enamel microstructure have involved three main areas of enquiry, with structural features having been investigated in relation to developmental mechanisms, function and/or phylogeny. The phylogenetic, or taxonomic aspect has been emphasized in the majority of studies involving the Order Primates, where efforts have focused upon attempts to recognise structural differences among various hierarchical groups. Studies of primate enamel microstructure by SEM are reviewed here, with emphasis on what has been learned concerning the most suitable preparative techniques that can be employed, and with particular emphasis to the relevance of enamel microstructure in taxonomic analyses of living and fossil primates. No one technique of enamel preparation can be held to be the most suitable for all types of material (e.g., fresh developing, wet mature, dry mature, and fossil enamel) but experience to date allows us to make some recommendations. Two aspects of enamel structure have been shown to possess considerable potential in taxonomic analyses: the enamel prism packing patterns, and the enamel formation rates as documented from prism cross-striation repeat intervals. Although the distribution of enamel prism packing patterns among primates suggests considerable homoplasy of this character, this feature does have considerable taxonomic interest at certain hierarchical levels in Primates. The study of rates of enamel secretion coupled with analyses of enamel thickness has considerable potential in resolving taxonomic and phylogenetic questions.