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Re: a little background



On Tue, Mar 12, 2002 at 05:04:56PM -0800, Jaime A. Headden sent:
> Graydon (graydon@dsl.ca) wrote:
> >What do you call the big sickle claws?  They're way overkill for
> >comparably sized critters.
> 
> Overkill? For what? No one has evidenciary proof except for
> *Velociraptor* using the claw for evisceration -- on a 8 ft
> *Protoceratops*. This _proves_ nothing about the use of such a claw in
> other dromies or even in *Velociraptor*, just one use. Many perching
> birds have such claws ... but do not use them to eviserate larger prey
> than themselves.

No perching birds have that kind of claw size disparity between claws on
the same foot, and so far as I am aware, no modern bird has a slashing
claw at all; the predatory birds all have _grasping_ claws, rather than
slashing ones.

It's a weapon or a scansorial climbing adaptation, by shape and form --
sharply pointed, strongly curved, laterally compressed -- and the
carriage, which can be infered from the lack of tip wear on recovered
claws.

So it's either a specialized climbing adaptation or a predatory one, or
some third thing where sharpness is of benefit.  Since the climbing
scenario makes no sense for arid environments, nor for an animal that
size, nor for a _single_ hyper mobile claw per foot, and there *is*
direct evidence for it being used as a weapon, the least hypothesis
looks very much like 'weapon', at least until someone can demonstrate
that there's ample strength in the joint to hook on and push up with one
foot for an eighty pound animal.

If it _is_ a weapon, it's much much larger than the teeth of the animal
it belongs to, when there is no reason to believe that those teeth are
inadequate to preying on animals of approximately the same size or that
evolving larger teeth was difficult in theropod lineages. It's attached
to the strongest muscles, much more powerful than jaw muscles, the
animal it belongs to has.

Given that the jaws were adequate to comparable sized organisms, what's
the benefit of the sickle claw mechanism to a predator _other than_
becoming able to attack larger prey?

-- 
graydon@dsl.ca   |  Hige sceal þe heardra, heorte þe cenre,
                 |  mod sceal þe mare þe ure maegen lytlað.
                 |   -- Beorhtwold, "The Battle of Maldon"