Abstract

In amniotes, daily rates of dentine formation in non-ever-growing teeth range from less than 1 to over 25 microns per day. The latter value has been suggested to represent the upper limit of odontoblast activity in non-ever-growing teeth, a hypothesis supported by the lack of scaling between dentine apposition rates and body mass in Dinosauria. To determine the correlates and potential controls of dentine apposition rate, we assembled a dataset of apposition rates, metabolic rates, and body masses for ca. 80 amniote taxa of diverse ecologies and diets. We used phylogenetic regression to test for scaling relationships and reconstruct ancestral states of daily dentine apposition across Amniota. We find no relationship between body mass and daily dentine apposition rate for non-ever-growing teeth in Amniota as a whole or within major clades. Metabolic rate, the number of tooth generations, diet, and habitat also do not predict or correspond with daily dentine apposition rates. Similar daily dentine apposition rates are found in large terrestrial mammals, dinosaurs, and marine reptiles, whereas primates, cetaceans, and some smaller marine reptiles independently evolved exceptionally slow rates. Life history factors may explain the evolution of dentine apposition rates, which evolved rapidly at the origin of major clades.