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Re: JFC-Bloodiest Battle ??

On Friday, August 22, 2008, at 04:44  PM, Dan Chure wrote:

Take a look at the dorsal view of the skull of Monolophosaurus or Sinraptor. While vertical loads might be accommodated, I am less certain about resistance to torque along the long axis of the preorbital region, especially given all the pneumatic penetration of the region.

They do indeed have quite narrow rostra. Resistance to torsion is related to the polar moment, however - the sum of the section moduli about any two orthogonal axes. In this case, that means that the lateral breadth and dorsoventral breadths both matter. So, allosaur skulls might be a bit weak under lateral bending loads, but I wouldn't expect them to be especially weak against torsion, as compared to an animal with a dorsally flattened skull (obviously a skull that's broad in both directions resists torsion the most). There is a bit of a difference imparted by the fact that the source of resistance is along a broad surface in one type, and a narrow one in the other, but the specifics of bracing and strain distributions around foramina will probably make a bigger difference in that regard.

(Note that the statements regarding torsional resistance are purely general and qualitative in this particular case - a precise relationship can be easily predicted for a long bone, or similar element, but skulls require something like FEA to get a real value).


--Mike H.

Michael Habib, M.S. PhD. Candidate Center for Functional Anatomy and Evolution Johns Hopkins School of Medicine 1830 E. Monument Street Baltimore, MD 21205 (443) 280 0181 habib@jhmi.edu