Re: Vestigial Arms (was: Theropod limbs - how mobile?)

[John Conway <john_conway@mac.com>]

On Sunday, May 19, 2002, at 01:50  AM, David Marjanovic wrote:

> "Maximum working range" = 199 kg for the biceps alone.

Haven't we got to be a little skeptical of such estimates? I wasn't 
aware that muscle strengths could be estimated with any degree of 
precision.

Even if they were that strong, they would still be ripped off by a 
struggling six tonne animal. I cannot envision tyrannosaurids struggling 
with their prey, it seems to risky for such large animals. To get their 
hand claws lodged in their prey would require tyrannosaurids to get very 
close, with wide areas of contact with their prey. At such close 
quarters, a simple shift in weight from the herbivore would throw the 
tyrannosaurid off balance, because its movement would be severely 
restricted. Falling over next to a panicked Triceratops or Anatotitan 
would be disastrous!

And if they were using their arms for such purposes, why were they so 
short?

It has been suggested before (sorry, I can't remember who it was) that 
they used their arms for intraspecific contests. The arms were small to 
keep them out of the way, and save energy growing them, yet they 
remained muscular for arm-wrestling with rivals.

You know it makes sense. ;-)

P.S.   Show me a convincing drawing showing a tyrannosaurid using its 
arms to subdue prey, and I will reconsider.

John Conway, Palaeoartist

"All art is quite useless." - Oscar Wilde

Protosite: http://homepage.mac.com/john_conway/
Systematic ramblings: http://homepage.mac.com/john_conway/phylogenetic/