Supplementary material from "Evidence of Bird-Like Foot Function in Tyrannosaurus"

The movement of extinct animals has been of long-standing interest, with Tyrannosaurus rex being a locus for this fascination. While the speed of T. rex has been of keen interest, the opportunity to study how T. rex details of footfall kinematics and their influence on pace length has not been taken. Here we present novel findings on the function of the foot of T. rex, using three predictive allometry based equations and several statistical tests including Kruskal-Wallis tests to reveal a complex and bird-like function of the foot. This includes a very bird-like gait defined by higher stride frequencies, proportionally short stride lengths, and elevated speeds. Comparisons between the four sampled specimens of T. rex with extant bipedal species are more akin to the gaits of the ground-truth modelled Struthio camelus and are notably divergent from the modelled Homo sapiens. Additionally, our models are consistent with recent studies suggesting slower to more intermediate top speeds for adult Tyrannosaurus that fall within the range of 5-11 m/s. This study lays the groundwork for future studies to add comparisons with additional theropods and potentially identify ecological differences between species.