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Cranial design and function in a large theropod dinosaur

Abstract

Finite element analysis (FEA)1 is used by industrial designers and biomechanicists to estimate the performance of engineered structures or human skeletal and soft tissues subjected to varying regimes of stress and strain2,3,4. FEA is rarely applied to problems of biomechanical design in animals, despite its potential to inform structure–function analysis. Non-invasive techniques such as computed tomography scans can be used to generate accurate three-dimensional images of structures, such as skulls, which can form the basis of an accurate finite element model. Here we have applied this technique to the long skull of the large carnivorous theropod dinosaur Allosaurus fragilis5. We have generated the most geometrically complete and complex FEA model of the skull of any extinct or extant organism and used this to test its mechanical properties and examine, in a quantitative way, long-held hypotheses concerning overall shape and function6,7,8. The combination of a weak muscle-driven bite force, a very ‘light’ and ‘open’ skull architecture and unusually high cranial strength, suggests a very specific feeding behaviour for this animal. These results demonstrate simply the inherent potential of FEA for testing mechanical behaviour in fossils in ways that, until now, have been impossible.

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Figure 1: The skull of Allosaurus fragilis.
Figure 2: Estimated bite forces and skull strength.
Figure 3: Stress distribution and vector plots for the skull of Allosaurus fragilis during a maximum impact bite without adductor muscle contraction (mode D).

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Acknowledgements

We are grateful to the Bozeman Hospital, Montana, USA, and Picker CT scan Company for CT scanning and file conversion; R. E. H. Reid for advice on dinosaur bone histology and material properties; and M. Harwood for COSMOS/M technical support. J. R. Horner provided access to Allosaurus fragilis (MOR 693), C. C. Horner provided use of computing equipment and aided file conversion; P. May Smith assisted with bite force calculations; S. Evans provided crocodile and alligator material for dissection and R. Felix advised on coordinate capture and image production. This work was supported by The Royal Society (D.B.N.), the Natural Environment Research Council, The Department of Earth Sciences and Emmanuel College, Cambridge University and the Cambridge Philosophical Society, and the British Federation of Women Graduates (E.J.R.).

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Correspondence to Emily J. Rayfield.

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Rayfield, E., Norman, D., Horner, C. et al. Cranial design and function in a large theropod dinosaur. Nature 409, 1033–1037 (2001). https://doi.org/10.1038/35059070

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