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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:
9. Pontzer, H., Allen, V., Hutchinson, J.R. 2009. Biomechanics of running indicates endothermy in bipedal dinosaurs. PLoS One 4(11): e7783. doi:10.1371/journal.pone.0007783 (link with open access)
A fusion of the methods of Pontzer (linking morphology and mechanics to metabolic cost) and Hutchinson et al. (estimating muscle mass requirements from morphology and posture), which infers that endothermic-level metabolism was ancestral to all dinosaurs and retained even by large taxa like Tyrannosaurus. This follows logically from our earlier finding that dinosaurs needed to have large active volumes of leg muscle even to walk; active leg muscle is metabolically costly which must be fueled by an active metabolism.
8. Gatesy, S.M, Baeker, M., Hutchinson, J.R. 2009. Constraint-based exclusion of limb poses for reconstructing theropod dinosaur locomotion. Journal of Vertebrate Paleontology 29:535-544. [pdf]
A new method building on the Hutchinson and Garcia (2002) and Hutchinson (2004a,b) models, which allows us to survey a very wide range of limb poses and identify which were less/more likely to have been used by different theropod dinosaurs. We find solutions that may have allowed Tyrannosaurus to run slowly (peak limb forces around 1.6-1.8 body weights or so), but still not very quickly.
7. Hutchinson, J.R. and Allen, V. 2008. The evolutionary continuum of limb function from early theropods to birds. Naturwissenschaften 96:423-448. [pdf]
Another review, but focusing on post-2000 studies of theropod dinosaur pectoral and pelvic limb function and evolution. This includes review of tyrannosaur locomotion studies by Sellers and Manning, Paul and others.
6. Hutchinson, J.R., C.E. Miller, G. Fritsch, T. Hildebrandt. 2008. The anatomical foundation for multidisciplinary studies of animal limb function: examples from dinosaur and elephant limb imaging studies. pp. 23-38 in H. Endo and R. Frey (eds.), Anatomical Imaging Techniques: Towards a New Morphology. Berlin: Springer-Verlag. [1.1pdf]
An essay on the importance of anatomy, including a new 3D biomechanical model of the muscle moment arms in the hindlimb of the dinosaur Velociraptor mongoliensis and comparison with Tyrannosaurus (see Hutchinson et al. 2005; paper #3 below).
5.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.
4. 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.
2. Hutchinson, J.R. 2004a. Biomechanical modeling and sensitivity analysis of bipedal running ability. I. Extant taxa. Journal of Morphology 262:421-440. [pdf]
1. 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
