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

----- Original Message -----
From: "Dann Pigdon" <dannj@alphalink.com.au>
Sent: Wednesday, May 22, 2002 2:15 AM

> You're assuming tyrannosaurs hunted alone.

Oh! True. Sorry. Good observation :-)

> Perhaps tyrannosaur-induced damage of hadrosaur tails was the result of
> a failed kill, where the hadrosaur managed to excape before the 'rex
> could take a piece out of the thigh or calf muscle to immobilise it.

Looks like it IMHO.

----- Original Message -----
From: "Dann Pigdon" <dannj@alphalink.com.au>
Sent: Wednesday, May 22, 2002 2:17 AM

> > if this is all what
> > *T. rex* did with its arms, why would it retain the claws?
> What selective pressure would there have been to lose them?

There's always a selective pressure to lose everything -- the energy used to
build and maintain it could go elsewhere. With that enormous amounts of
cortical bone and muscle, tyrannosaur arms don't look vestigial. They're
"reduced to the max" :-)

> I like the idea that the forelimbs were used during copulation. That's
> the only reason why pythons and marine turtles still have grasping
> devices.

I'm thinking about whether this would imply sexual dimorphism (probably not
testable because of the sample size)... and whether it's possible to hold a
tyrannosaur with such hands without inflicting serious wounds to it. :-/