Re: Dino Knees

[Betty Cunningham <bettyc@flyinggoat.com>]

Rob Meyerson wrote:
>  I suspect that the main reason for this type of limb construction is that 
> the leg and upper 
> foot acted as a shock absorber between the ground and the body.   To return 
> to my horse
> comparison, this type of limb arrangement can be found in animals that are
> rather fast on their feet.  To *really* go out on a limb (no pun intended), 
> one
> could say that this would mean that, like horses, theropods not only could run
> fast, but did so frequently; possibly another point for the high-metabolism
> theropod model.

   the center of gravity changes with the shape of the WHOLE animal, and you 
can't use a 
quadrepedal metaphor for a bipedal animal because the weight support is all 
wrong. 
   Horses have more vertical lines in their lower rear legs, therapods are more 
vertical until 
the ankles.  Horses are not the right comparison as they have two more 
EXTREMELY vertical front 
legs to catch and hold the weight of their forwards momentum and to reach out 
and grab more 
ground.  The back legs serve only to push the weight forwards adn hold up the 
back half of the 
naimal, the front bears the weight of the head and neck as well as grabbing 
ground to do some 
slight pulling along of the body.
  The therapod hasn't got anything extra to JUST grab ground, or JUST push 
weight along, so look 
at BIPEDAL forms for proper comparison.  Like ostriches, people, ground sloths, 
and kangaroos.  
Then eliminate the kangaroos 'cause they have (except one species of kangaroo) 
a fused hip that 
doesn't allow individual leg movement but rather dual 'locked-step' movement, 
and eliminate the 
ground sloth as it was probably moving as a quadreped and sit/standing to feed.

-Betty Cunningham