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The Science of Sue
Fleshing Out The Picture
The study of locomotion of T. rex was carried out by calculating forces acting at skeletal joints. Actual muscle configurations were not applied, but the beautifully preserved surfaces of SUE’s hip and leg bones show clear evidence of where the major muscles of the hindlimb attached. The placement of these muscle scars has been combined with knowledge of muscle position in living archosaurs (crocodilians, birds) and evolutionary theory to reconstruct the gross muscle anatomy of SUE’s hips and thighs.
This research has corrected previous ideas about the placement and role of theropod hindlimb muscles and has revealed how T. rex and other theropods had already evolved some bird-like muscle configurations. For example, SUE’s hipbone is greatly enlarged relative to those of primitive theropods, thus serving as an anchor for larger muscles that moved the thigh and shank. Expansion of the hipbone meant longer lines of action for these muscles and hence greater rotation of the knee and hip joints, suggesting that T. rex and its kin were more agile than more primitive theropods, for a given body size, and mark an intermediate stage in the evolution of avian knee-based locomotion. Questions that have been cleared up include the identity of the muscles that attached to a series of processes and muscle scars near the hip-end of the thigh bone. By understanding the identity—and therefore the lines of action of these muscles—it will be possible to construct more detailed models of theropod locomotion and further refine our understanding of what limits and ranges of movement were available to these animals.
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