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Re: Evolution of tyrannosauroid bite power

----- Original Message ----- From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Sunday, December 30, 2007 3:45 PM
Subject: Re: Evolution of tyrannosauroid bite power

Don Ohmes wrote, in part:


that a relatively large and powerful head was absolutely essential to life style, because it is relative >arm length that decreased (even while the arms remained strong), rather than relative head size.

"Strong" is a relative term. Carpenter and Smith (2001) estimated the maximum force capable of being generated by the M. biceps in T. rex to be about 1955 N, or about 199 kg (440 pounds) per arm. Although grasping 900 pounds or so may sound "strong" in absolute terms, in relative terms (assuming a 6000-7000 kg mass for an adult T. rex) it equates to me (a 200 pound person) being able to curl about 12 pounds, using both arms. I think the question is not why T. rex arms were so "strong", but why were they so weak?