The ontogeny of bite‐force performance in American alligator (Alligator mississippiensis)

Abstract

American alligators Alligator mississippiensis undergo major transformations in morphology and ecology during development. These include several thousand-fold changes in body mass, modified snout and dental proportions, and shifts in diet from small, delicate foodstuffs to the inclusion of increasingly larger, more robust prey. How these changes in anatomical form contribute to actual physical performance and niche use is largely unknown. In the present study, bite-force measurements for 41 specimens of A. mississipiensis, were made throughout ontogeny (hatchling-older adults) using a series of precision force transducers. How this performance indicator scaled with respect to cranial and whole-body measurements was determined. Bite-force production throughout development was contrasted with ontogenetic changes in trophic ecology. The influences of this performance measure on these changes were then analysed. The results showed a 800-fold range (12-9452 N) of bite forces with values positively correlating with increases in body size. Scaling of biting forces through ontogeny showed positive allometry with respect to body mass, head length, jaw length, snout-vent length and total length. These patterns may be attributable to allometric growth of individual skeletal elements (and associated musculature), and/or progressive fusion and ossification of skull and jawbones during development. The overall pattern of force increase throughout ontogeny did not vary in association with major shifts in diet. Notably, the bite-force values for adult A. mississippiensis are the highest measured for any living animal and represent the first measures for a large crocodilian. Additionally, these data provide the first documentation of how bite force changes during ontogeny in a reptile. By bridging the rich morphological and ecological databases for these animals, this study opens the door to a comprehensive understanding of feeding in A. mississippiensis. Furthermore, it provides groundwork for standardized comparative studies of feeding among crocodilian, reptilian, or other gnathostome vertebrates.

Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics

“…Our human bite forces (700-1020 N) overlap experimental values of 730-749 N [5,6] and lie within estimates in earlier modelling studies of 678-1080 N [7,8], with variability across studies attributed to significant variation in muscle size between individuals and the level of muscle activation associated with different biting activities [5][6][7][8]. Erickson et al [13] (b) Bite performance in Tyrannosaurus rex We are aware of two previous quantitative estimates of bite force in T. rex. Indentation experiments, which estimated the force required to replicate a fossilized bite mark, produced values of 6400-13 400 N for a single posterior tooth [4].…”

Bite‐force performance of the last rhynchocephalian (Lepidosauria:Sphenodon)

“…Assuming isometric growth, and employing a linear model on log-transformed data, scaling predictions indicate that bite force should scale on linear morphometrics with a coefficient (i.e., slope) of 2.0 (e.g., Erickson et al 2003). This prediction is based on the fact that the primary gross predictor of muscle force is the cross-sectional area of the muscle in question.…”

“…This prediction is based on the fact that the primary gross predictor of muscle force is the cross-sectional area of the muscle in question. Despite this straightforward prediction, the results of all studies of non-avian reptilians to date are that bite force scales with significant positive allometry (i.e., slope of >2.0) on linear measures of body and head size (e.g., Cnemidophorus (New World scleroglossan lizard) = 3.8 (Meyers et al 2002); Sceloporus (New World iguanian lizard) = 4.6 (Meyers et al 2002); turtles = >3.0 , and Alligator mississipiensis = >2.6 (Erickson et al 2003(Erickson et al , 2004). Bite force in agamid lizards (87 individuals of 9 different unspecified species), the group with which juvenile Sphenodon were compared by Schaerlaeken et al (2008), also appears to scale with positive allometry, though an equation for the linear relationship was not provided.…”

“…Assuming isometric growth, and employing a linear model fitted to log-transformed data, bite force should scale on any linear morphometric with a coefficient of 2.0 (e.g., see Erickson et al 2003). This prediction is based on the fact that the primary gross predictor of muscle force is the cross-sectional area of the muscle in question, and that measurements of anatomical areas scale on linear anatomical dimensions (e.g., body length, head length) with a coefficient (i.e., slope) of 2.0.…”

The birdlike raptor Sinornithosaurus was venomous

“…The maxillary teeth of Sinornithosaurus are long enough to reduce bite force (18) and restrict the size of prey that will fit in its gape. Sinornithosaurus had a strikingly heterodont dentition that placed restrictions on its use as a simple "grab and gulp" mechanism.…”