A comparative analysis of ontogenetic bite-force scaling among Crocodylia

Interspecific adult bite forces for all extant crocodylian species are now known. However, how bite forces scale during ontogeny across the clade has yet to be studied. Here we test the hypotheses that extant crocodylians share positively allometric and statistically comparable developmental scaling coefficients for maximal bite-force capacity relative to body size. To do this, we measured bite forces in the Australian freshwater crocodile Crocodylus johnsoni and the Saltwater crocodile C.porosus, and determined how performance changed during ontogeny. We statistically compared these results with those for the American alligator Alligator mississippiensis using 95% prediction intervals and interpreted our findings in a phylogenetic context. We found no observable taxon-specific shifts in the intraspecific scaling of biomechanical performance. Instead, all bite-force values in our crocodylid dataset fell within the bounds of the A.mississippiensis 95% prediction intervals, suggesting similar bite-force capacity when same-sized individuals are compared. This holds true regardless of differences in developmental stage, potential adult body size, rostro-dental form, bone mineralization, cranial suturing, dietary differences or phylogenetic relatedness. These findings suggest that intraspecific bite-force scaling for crocodylians with feeding ecologies comparable with those of extant forms has likely remained evolutionarily static during their diversification.