Re: Evolution of tyrannosauroid bite power

[ptnorton <ptnorton@suscom-maine.net>]

----- 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:

*Snip*

> 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?

PTJN