The fastest gait and speed of the largest theropod (carnivorous) dinosaurs, such as Tyrannosaurus, is controversial. Some studies contend that Tyrannosaurus was limited to walking, or at best an 11 m s-1 top speed1,2,3,4, whereas others argue for at least 20 m s-1 running speeds5,6,7. We demonstrate a method of gauging running ability by estimating the minimum mass of extensor (supportive) muscle needed for fast running. The model's predictions are validated for living alligators and chickens. Applying the method to small dinosaurs corroborates other studies by showing that they could have been competent runners. However, models show that in order to run quickly, an adult Tyrannosaurus would have needed an unreasonably large mass of extensor muscle, even with generous assumptions. Therefore, it is doubtful that Tyrannosaurus and other huge dinosaurs (∼6,000 kg) were capable runners or could reach high speeds.
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We thank F. C. Anderson, K. Angielczyk, S. Delp, R. J. Full, S. M. Gatesy, T. M. Keaveny, R. Kram, K. Padian and J. F. Parham as well as the Berkeley Biomechanics and Stanford Neuromuscular Biomechanics seminars for input. J.R.H. appreciates funding from the University of California Department of Integrative Biology and Museum of Paleontology, and the National Science Foundation under a grant awarded in 2001. M.G. had postdoctorate funding through a DARPA grant to the Polypedal Lab at UC Berkeley. This is University of California Museum of Paleontology publication number 1749.
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Hutchinson, J., Garcia, M. Tyrannosaurus was not a fast runner. Nature 415, 1018–1021 (2002). https://doi.org/10.1038/4151018a
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