Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation (original) (raw)
Figure 4
Caniniform pressure values for extant Crocodylia, their phylogenetic distribution, and inferred ancestral character states.
(A) Members of the Alligatoridae are shown in blue, and members of the Crocodylidae+Gavialidae in green. The OLS regression equation describes the weak relationship between body mass and caniniform pressure. Note that slender-snouted piscivorous to semi-piscivorous ecomorphs (Gavialis gangeticus and Crocodylus intermedius, respectively) show exceptionally high-pressure values (outside the 95% confidence interval), and Crocodylus johnsoni shows pressures expected of animals nearly a magnitude in size larger. Other ecomorphs show much lower and similar relative values. The arrow indicates the typical ultimate shear strength of bone. (B) Ancestral character-state reconstruction using squared-change parsimony of size-standardized caniniform pressures. Residual caniniform pressure values are color coded to MPa (squared-change parsimony; squared length = 19.491). Vertical scale is in relative time, with the outgroup/ingroup root arbitrarily set to 1.0. High relative pressures were achieved independently in Crocodylus intermedius, Gavialis gangeticus, and Crocodylus johnsoni. Uncolored branches represent taxa for which the caniniform teeth were shed or broken, and so pressure estimation was not possible.