FIG. 3 in Bite-force estimation for Tyrannosaurus rex from tooth-marked bones

FIG. 3 Maximum penetration force values for an adult Tyrannosaurus rex tooth replica impacted through bovine ilia with varying cortical thickness. Peak penetration forces increased with increasing cortical thickness (y = 2305.402x + 646.634, r 2 = 0.91). METHODS Because of the 7-fold range of peak force values in the simulations, it was necessary to obtain precise measurements of the cortical depths penetrated by the T. rex teeth. A bone sample taken adjacent to the deepest bite mark revealed a 2.5 mm cortical thickness, From the regression equation, approximately 6,410 N offorce was required to produce the bite mark. This bite mark was made by one of the tyrannosaur's longer caniniform teeth 8, probably a tooth between the fourth and seventh maxillary positions (based upon American Museum of Natural History specimen AMNH 5027, New York). To account for the relative mechanical advantage of more posteriorly positioned teeth 27, moment calculations were used to calculate the simultaneous forces produced at the most posterior tooth positions. Values ranging from 7,870-10,300 N were projected, assuming 6,410 N of force were produced simultaneously by teeth from the fourth to seventh tooth positions. Because bone strength increases with strain rate 28 and the penetration rate of the tooth replica was just 1 mm s- 1, it is likely that the simulation force values underestimated actual forces. A tooth-impact velocity of 10 mm s-1 for a biting tyrannosaur (based on extant large reptile feeding; G.M.E., personal observations) would have required ~20% more bite force 28 • Adhering flesh 8 may have absorbed another 10% (or more) of the initial bite force 29. These considerations suggest that bite forces as high as 13,400 N could have been produced by an adult T. rex during feeding. Greater forces may have been possible during snapping bites or those involving bodily inertia to augment tooth penetration. Such biting is characteristically used when prey are seized initially (G.M.E., personal observations of reptilian feeding). Taphonomic interpretations suggest that the bite marks on the Triceratops ilium were not the result of this behaviour8. Additionally, if the tyrannosaur's contra lateral teeth were used when the deepest bite mark was made, greater bite forces may have been generated than those we estimated 13·30. This is indeterminable from MOR 799.