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Re: cause of Gigantism in sauropods



Good thoughts.  A quick clarification here is needed, however. The cervicals of 
sauropods had fragile walls from a preservation standpoint. Mechanically, 
however, they were generally quite strong in bending. In order to maintain this 
strength in bending at large body sizes,  where structural constraints are more 
intense, without excessive mass, the vertebrae must be thin walled which makes 
them weak to local impact. However, in mechanics "local impact" means something 
more akin to point loading. When using the neck as a weapon, or having it 
pulled on by a predator, bending loads would dominate.  By contrast, an animal 
being struck by a weapon (club, spike, tail, etc) is likely to suffer a local 
impact.

Safety factors in bending and impact both tend to be a bit lower in large 
animals than very small ones, and larger animals often rely on maintaining 
specific loading regimes to keep structural loads within reason (example: 
keeping limbs in compression, rather than bending).

Cheers,

--MH

Sent from my iPhone

On Feb 12, 2011, at 3:40 PM, "Augusto Haro" <augustoharo@gmail.com> wrote:

> We might also say that, being the cervicals as delicate as Mike said,
> the sauropod would get its neck severely damaged if hitting a theropod
> head, I would gess (although math would be necessary). This would be
> more true considering, as Michael indicated, that the sutructure of
> larger animals is relatively less resistant against blows.
> Now I want to ask: is there a way to differentiate predation marks
> from scanvenging marks? Because, if the cervical vertebrae are
> fragile, as said above, it would be difficult for a bitten animal to
> survive (I suppose), and thus the presence of toothmarks with
> posterior growth may be less expectable. So, lack of bite marks which
> are not scanvenging ones would not necessarily imply that theropods
> did not attack large sauropods.