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In this section:
See Also:
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An artist's conception by Luis Rey, illustrating the similarities and differences between a 6000 kg tyrannosaur and chicken. Please credit Luis Rey if you use this image anywhere, copyright 2002. |
A newer 3D model of the right hindlimb of Tyrannosaurus, showing how a more realistic model than the one used in the paper can examine individual muscles in more detail. Assistance was kindly provided by Celeste Horner (scanning the skeleton), Anh Phuong Le (initial editing), Christine Gatchalian (extensive editing and formatting), and Brian Garner (final formatting and decimation). Please credit John R. Hutchinson if you use this image, copyright 2002. |
See also newer studies relating back to the original Nature paper:
1.
Hutchinson, J.R., V. Ng-Thow-Hing, F.C. Anderson. 2007. A 3D interactive method for estimating body segmental parameters in animals: application to
the turning and running performance of Tyrannosaurus rex. Journal of Theoretical Biology 246:660-680. [pdf]
Here we constructed 30 models of the whole body of Tyrannosaurus rex to estimate its mass, center of mass, and inertial tensor values. We varied the shape of the body and its internal cavities in a detailed sensitivity analysis, and found good validation for the method using an ostrich. We then used our results in two biomechanical calculations, showing that it would take some 1-2 seconds to turn 45 degrees on one leg, and that it still could not run very fast even with some changed parameter values. Mass was ~6000-8500kg, the center of mass was 0.45-0.75m in front of and ~0.3m below the hips, and inertias in yaw and pitch were immense.
2. Hutchinson, J.R. 2006. The evolution of archosaur locomotion. Comptes Rendus Palevol 5:519-530. [pdf]
This is a general review of the changes of limb anatomy and function from basal reptiles through archosaurian reptiles (incl. birds) but also illustrated using simple biomechanical models how, if we knew the joint angle of an animal's limb reasonably well, we should be able to bound its overall limb posture fairly tightly (~20deg range) as the limb joints are interdependent; only some combinations of joint angles are viable..
3. Hutchinson, J.R., F.C. Anderson, S. Blemker, S.L. Delp. 2005. Analysis of hindlimb muscle moment arms in Tyrannosaurus rex using a three-dimensional musculoskeletal computer model: implications for stance, gait, and speed. Paleobiology 31:676–701. [pdf]
We developed a highly detailed anatomical model of all the major hindlimb muscles in T. rex, which allows us to estimate what its moment arms (leverage) of different muscle groups was, and how these depended on posture. We found that more upright (straight-legged) poses had greater moment arms for supporting body weight, and hence T. rex might have used more extended (but not fully columnar) limbs. We also found that my earlier analyses generally used overestimates of the moment arms of antigravity muscles, which biased our results toward favoring faster running speeds, and hence actually strengthened our conclusions that it was not a fast runner.
4. Hutchinson, J.R. 2004a. Biomechanical modeling and sensitivity analysis of bipedal running ability. I. Extant taxa. Journal of Morphology 262:421-440. [pdf]
5. Hutchinson, J.R. 2004b. Biomechanical modeling and sensitivity analysis of bipedal running ability. II. Extinct taxa. Journal of Morphology 262:441-461. [pdf]
These two linked studies are especially important as many input and output parameters from the original 2002 Nature study were improved here. I strongly validated the modeling approach with multiple extant animals (birds, mammals, and reptiles), finding that ankle muscle mass seemed to typically be most limiting for speed. My estimates of muscle masses needed for Tyrannosaurus rex to run quickly were smaller (~20-35% body mass per leg) but still too high to allow very fast running, which I estimated as over 11m/s (25mph). Further validation for the approach was provided by showing that smaller dinosaurs could indeed run quickly (as known from footprints), and relative (and perhaps absolute) running performance dropped with size (above ~1000kg).
John Hutchinson Staff Home Page Structure & Motion Lab
