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Re: Diplodocus: Return to the Swamps????



--- On Mon, 12/14/09, Jonas Weselake-George <Paleo@ncf.ca> wrote:

> From: Jonas Weselake-George <Paleo@ncf.ca>
> Subject: Re: Diplodocus: Return to the Swamps????
> To: dannj@alphalink.com.au, dinosaur@usc.edu
> Date: Monday, December 14, 2009, 1:13 AM
> 
> Dann Pigdon <dannj@alphalink.com.au>
> wrote:
> "It goes in splayed with plenty of resistance (limiting the
> depth of penetration), but is drawn out with converged toes
> that offer far less resistance. Sauropods, on the other
> hand, would have had to fight each step to extract a foot
> from deep mud. That's bound to tire a large animal out after
> a while."
> 
> What about taking into account mass (and muscle mass) vs.
> limb surface area? It would seem to me that a fifteen ton
> sauropod would experience less relative suction than a one
> ton theropod. What do you think? 

Exactly. Re is critical (or perhaps some related but more situation-appropriate 
and specialized metric). Mud is essentially less dense/viscous for larger 
animals...
  
> Additionally, the sauropod would tend to punch through to
> the substrate more easily and would also have four limbs for
> balance. I'm not arguing that it'd be easy, but a large
> sauropod might have an advantage in moving through a swamp
> (not that it is very likely a theropod one fifteenth its
> weight would have a motivation to follow). 

Don't forget that repeatedly sheared mud tends to liquify. In other words, if 
you have the power to shear it in the first place, it becomes easier w/ each 
shearing. And less supportive to any splay-footed interloper. 
 
> A more likely situation would be sauropods taking advantage
> of the mud to mate (after all I saw a paper suggesting that
> an early cretaceous ornithopod population was using swamps
> for shelter during the breeding season).

What is unlikely about a theropod-free zone?

Anyhow, to bed for me...