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Re: Evolution of tyrannosauroid bite power



I agree. Whatever it was doing with its arms was risky business. Attributing such damage to display behavior does, however, explain why such damage was apparently not necessarily fatal. My understanding of the literature is that most of these M. bicep avulsions show signs of healing. If the arms were being used for something as critical to survival as prey capture, we would not likely see that. If you can't grab your meal, you can't eat. If it was related to display behavior, however, the animal was probably much more likely to survive, although they might have been lower on the hierarchical dominance "pecking order" than they were before.

PTJN

----- Original Message ----- From: "Graydon" <oak@uniserve.com>
To: <dinosaur@usc.edu>
Sent: Tuesday, January 01, 2008 5:12 PM
Subject: Re: Evolution of tyrannosauroid bite power



On Tue, Jan 01, 2008 at 05:14:00PM -0500, ptnorton scripsit:
Carcass lifting is a plausible alternative hypothesis to prey
grappling as an explanation for forelimb function in T. rex, given the
strength parameters so nicely described by Carpenter and Smith (2001).
Carcass lifting is biomechanically possible, consistent with
behavioral science with respect to the nearly ubiquitous presence of
dominance display

I have some doubts about this.

We know for sure that whatever T. rex was doing with its forearms
damaged them.

While damage from direct dominance *competition* is common, damage from
display behaviour is not.  (And even in the case of dominance
competition, there's a lot of selection pressure against permanent
damage, presumably because no organism starts as the dominant bull
equivalent.)

I would suggest that making a claim of display behaviour commonly
leading to damage is a very strong claim, because this is an extremely
uncommon behaviour across tetrapoda.

-- Graydon