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RE: arm movement (wasRe:book review)



nick said:

>        I've been thinking about dinosaur climbing, using
> dromaeosaurs.  What I've been tossing about in my head is this-
> swing the arms, palms inward toward the trunk of a tree. Then bring
> the legs up, and kick in with the hyperextendible second toe, into
> the bark- when you've got a grip, extend the arms up further, latch
> on, and then raise the legs up again. In this way, a theropod could
> climb, without having to evolve the sprawling stance of a squirrel,
> but which would get the forelimbs way out to the side- also
> effectively preventing the evolution of a fore-hind limb
> patagia. The motions are more or less similar to what the animal
> would use in killing it's prey, actually. I don't know how actually,
> anatomically, feasible this would be.

I like the idea. It's sort of how telephone repair men climb, but with   
the spikes in line with the body not perpendicular to it.  (they use a   
rope around the trunk of the pole that they slide up when the   
ankle-spikes they wear are dug in for support, then they hang on to   
either end of the rop while they move their legs up to spike for the next   
grip.  Bear cubs climb trees sort of like this, too)
If I try to simulate the move myself, and I go up to a pole and press my   
hands to the sides of the pole without GRASPING it with my fingers, the   
big muscle-use is felt in my pecs and triceps, and with major pressure on   
the butt of the palm (on the side away from the thumb where the bones of   
my hand are sort of left off being knobby) and the bent wrist itself.  I   
am standing here looking at a pole (this is for SCIENCE, man), with my   
elbows bent and pointed straight out to the sides in order to use the   
muscles to press IN to the pole.
How does the musclature compare on a dromaeosaur?
How much bend is the wrist capable off?  Mine is at a 90 degree angle to   
my arm.
Could they do this with straight arms?

[ We've been down this road a few times already, and consensus always
  seems to to end us on the conclusion that if telephone repairmen had
  to deal with branches and a broomstick on their butts, they wouldn't
  be able to climb so well... -- MR ]

 -Betty