Introduction

Dental morphology has been the most important source of data for the interpretation of both phyletic relationships and dietary behaviors of extinct mammals. Differences in gross dental shape have traditionally contributed most of this information, although the complexity of enamel structure was recognized in the last century as subsequently were patterns of enamel microstructural differences among diverse mammalian taxa (Kawai, 1955).

However, it has only been in recent years that relationships of enamel microstructure to dental function have been identified (Walker et al., 1978; Koenigswald, 1980; Rensberger and Koenigswald, 1980; Pfretzschner, 1988; Maas, 1991). The organization of the enamel microstructure is now known to have an adaptive relationship to the stresses generated during mastication and other uses of the teeth, indicating that these structures can be used to make inferences about differences in dietary behavior in extinct taxa.

An increased interest in enamel structure in the past two decades is contributing to a greatly expanded knowledge of the microstructure. As the structures in larger numbers of taxa have been clarified, the diversity of known microstructural conditions has increased. This has resulted in an increasingly complex picture of phyletic evolution that is clearly not explained by one-to-one relationships of structure and diet. For example, some highly specialized structural conditions occur in unrelated living taxa with quite different gross dental specializations and dietary behaviors. Nevertheless, even in such cases there may be functional components that are shared and may explain the microstructural similarities.