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Re: Evolution of tyrannosauroid bite power

Keeping it simple; given that all theropods were constructed of the same 
materials, wouldn't relative arm size be expected to generally decrease as 
overall size increased, irregardless of the implications of diet?


----- Original Message ----
From: ptnorton <ptnorton@suscom-maine.net>
To: Dinosaur list mail <dinosaur@usc.edu>; tholtz@umd.edu
Sent: Saturday, December 29, 2007 2:07:39 PM
Subject: RE: Evolution of tyrannosauroid bite power

Tom Holtz wrote on Thu, 20 Dec 2007 08:25:19 -0500

>Well, of course, and I think everyone working on this would agree
>with that scenario.
>But a biomechanical analysis must needs focus on one particular part
 of the
>organism, and later be integrated into other comparable systems.

That is the traditional approach, but methods for analyzing the motion
complex (i.e., multi-part) mechanical *systems* are being developed
show a lot of promise for analyzing biomechanical systems. The 
methodological problem in analyzing each part of an animal separately
that the parts are not independent of one another.  Analyzing them as a
complex biomechanical system with multiple dependent parts is an effort
get away from that problem. For an example from mechanics, see Hong and
Cipra's 2003 paper illustrating a method to analyze the motion of
cable-pulley systems, which can be found on-line at 
It's probably not the best example, but it's useful for illustrating
distinction I was trying to make. It seems to me that the relationship 
between arm size and bite power, or arm strength and hip strength,
some real potential for using this type of systems analysis.


The axes of truth and utility are not coincident.