Incremental geochemistry of extant crocodylian teeth: the need to establish a time frame

In the framework of this project, incremental δ18O and 87Sr/86Sr values (linked with living environment) as well as δ44/42Ca and δ15N values (linked with diet) have already been measured on teeth belonging to three different taxa of extant crocodylians. As those measures were made incrementally along the growth axis, they correspond to a time frame, that is the one of the tooth mineralisation rate of the specimen. Daily increments of dentine that are separated by the lines of Von Ebner1, can be counted on thin sections under light microscope to estimate the time represented in the whole dentine of each specimen, and the precise time recorded by each sampling point. Once variations in isotopic compositions (and thus ecology) will have been related to a time frame, this method will be applicable on fossil specimens tease apart the influence of ecological and environmental parameters.