The chemical compositions of dentine and enamel from recent reptile and mammal teeth - variability in the diagenetic changes of fossil teeth

Principal component analyses, based on microprobe data and coupled with microstructural observations, have been applied to investigate the differences between teeth of recent and fossil mammals and reptiles, and their fossil counterparts. In recent samples, enamel is compositionally distinct from dentine, and differences also exist between mammal and reptile teeth. During fossilization, both the physical structure and chemical composition of enamel and dentine can be altered, the degree and extent of which varies from site to site, depending on the nature of the burial environment. The higher porosity of the dentine structure allows for a more open pathway for fluids within the burial environment to permeate more efficiently. Subsequently, dentine is often considered to be more susceptible to diagenesis than enamel. However, enamel from one fossil site has undergone significant diagenetic alteration. Because of the variable and unpredictable effects of diagenesis, the chemical composition of fossil teeth is not a reliable indicator of the lifetime (i.e. in vivo) composition. Thus, interpretation of the lifestyle or environment of individuals that is based on compositional parameters, such as palaeodiet, needs to take into account the degree and extent of diagenetic alteration associated with individual fossil sites. Additional factors that can affect post-mortem alteration of teeth, are the mechanical and chemical modifications that result from predation and digestion.