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Re: Vestigial Arms (was: Theropod limbs - how mobile?)
On Sunday, May 19, 2002, at 05:13 AM, David Marjanovic wrote:
Oh, sorry. Forgot to write that: Muscle attachment sites. How big are
and where exactly are they? What diameters would the tendons therefore
and at what angles would they be positioned? What would various
advantages be? That sort of thing. All quantifiable.
This can be put in simpler terms. Ceratopsid of hadrosaurid legs
powering escape, vs tyrannosaur arms preventing it. Compare the bone
strengths and muscle masses: legs win, by a long, long way.
Which was the purpose -- the prey shouldn't move, and only the
head and neck should move :-)
Movement is necessary for the predator to maintain balance. They prey is
NOT going to stop moving its legs because tyrannosaurid arms are lodged
in its back (well not right away anyhow).
Hm. My center of gravity is maybe half a meter above my hip joints
of between them, and I don't have a tail. And *T. rex* can stop anyone
thrashing about :-)
Well, tie a couple of big dogs together, same result, I think. Legs get
tangled when they cannot move through their full arc.
If a tyrannosaurid's prey lurched toward it, then one leg would go
underneath the herbivore, and it would not be able to swing its tail far
enough to correct its balance, because the preys body or tail would be
in the way.
What's the point of such risky hunting techniques anyway? The bite size
GSP calculated in PDW looks big enough to fell a Triceratops without
repeated biting or grappling.
It would explain the pulling muscles if they stood side by side, and
hooked hands, trying to pull each others arms outward.
Very difficult according to Fig. 9.13C. The claws point inwards, and any
rotation of the forearm is impossible.
This is what I am picturing. I'll draw a picture.
John Conway, Palaeoartist
"All art is quite useless." - Oscar Wilde
Systematic ramblings: http://homepage.mac.com/john_conway/phylogenetic/