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Re: Sickle Claws (was "a little background")



"Jaime A. Headden" wrote:
> 
>   I'd like to think that the large, recurved claw on the toe of the
> cassowary...

>From what I've seen, they're not recurved. They're shaped more like a
straight-bladed carving knife.

I believe the shape difference between dromie second pedal claws and
those of cassowaries is due to the cassowary bearing weight on theirs
(at least as much as the other toes), whereas evidence seems to support
a retracted claw in dromaeosaurs. Cassowaries use their toe claws quite
well without requiring a large arc of articulation of their second toe.
Perhaps the ability to retract the second pedal digit in dromaeosaurs is
due to them being retracted normally during locomotion. Certainly they
could have used them for slashing or ripping purposes without the need
for such an extended arc of articulation. That to me suggests dexterity
of use, for delicate operations, rather than forceful slashing (where a
less-yeilding toe like that of a cassowary would seem to be a better
adaptation).

> ... This does not require the prey to be
> so much larger than the predator and does not then serve any objective
> evidence for dromies feeding on larger prey.

Indeed. Rather than think of pedal sickle claws as weapons, perhaps the
word "tool" would be of more use. I've often commented on the similarity
in shape between said sickle claws, and the beaks of "true" raptors.
Perhaps they were used more for tearing apart a carcass than for killing
(or maybe  used just as much, or instead of). Deinonychus didn't need to
kill a Tenontosaur to feed on it if it were already dead, but that
second toe claw would have been dandy for getting through the hide to
expose the more tender cuts of meat.
-- 
________________________________________________________________

Dann Pigdon                   Australian Dinosaurs:
GIS Archaeologist           http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
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