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Re: T. rex vs Edmontosaurus speed



Hutchinson's work on T. rex hip and leg extensor muscle mass is more subtle than you suggest. As I understand his work, he finds that a hip and leg extensor muscle mass of 10-20% of total body mass is not sufficient to produce fast running in T. rex. If there is a weakness in his work, it is that he models those muscles as cylinders rather than as more efficient and realistic shapes such as ellipsoids or bicones. Modeling muscles as cylinders has the effect of significantly under-powering those muscles per unit of mass. If Hutchinson repeated his analysis using a different model of muscle shape, my bet is that he would find a T. rex more capable of fast running than he originally thought. And if the absolutely larger hip and leg extensor muscle mass suggested by this new fossil holds for T. rex, even faster yet.

PTJN

----- Original Message ----- From: "Martin Baeker" <martin.baeker@tu-bs.de>
To: "jrc" <jrccea@bellsouth.net>
Cc: <trex_kid@hotmail.com>; "dinosaur mailing list" <dinosaur@usc.edu>
Sent: Friday, December 14, 2007 7:55 AM
Subject: Re: T. rex vs Edmontosaurus speed



It's not quite that simple - first of all, it is not absolute muscle mass, but muscle mass relative to body weight that is important, i.e., how large is the percentage of the body mass that is concentrated in the muscles. Furthermore, there is the question of how the muscles act - moment arms of the muscles and length of the limb segments.

If you want to see how to calculate with this kind of things, look at
the papers by John Hutchinson.

Cheers,

Martin.

Re speed vs. musculature, let's for the moment make a loose general analogy
with other animals, horses for example. If musculature is directly related to
speed, that would imply that Belgians, Percherons, and Clydesdales are faster
than Thoroughbreds. Is that in fact, the case? In a similar vein, would a
mastiff be expected to outrun a greyhound or whippet?
JimC


----- Original Message ----- From: "Brandon Pilcher" <trex_kid@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Thursday, December 13, 2007 7:50 AM
Subject: T. rex vs Edmontosaurus speed



> >including the conjecture that it could have outrun T. rex (based on >examination of Dakota's muscles).




Priv.-Doz. Dr. Martin BÃker
Institut fÃr Werkstoffe
Technische UniversitÃt Braunschweig
Langer Kamp 8
38106 Braunschweig
Germany
Tel.: 00-49-531-391-3073
Fax 00-49-531-391-3058
e-mail <martin.baeker@tu-bs.de>