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Sickle claws



[ Before approving this message I cut out about a third of the
  material that Peter had previously quoted.  Come on, people, you can
  do better editing jobs!  -- MR ]
 
Sam Girouard wrote:

>         First, several living birds have modified toe claws to suit various
> tasks. Herons have bizzare comb-like medial claws that they use for
> preening. Cassowaries and rheas have toe claws that they often use for
> combat, much in the same manner that is postulated for dromaeosaurs.

I believe one of the major reasons sickle clawed theropods are thought to 
have carried their claws above the ground is because they have peculiar 
articulations on the toe bones that seem to let the toe sit hyperextended.  
Also, the claw toes have been shortened.  One quite telling feature is that 
the other two walking toes have become nearly equal in length, presumably for 
stability, and the foot bones have been reinforced.  As far as I know, 
cassowaries and rheas have none of these additional modifications.

>         Second, and perhaps more importantly, I know of no distinct,
> irrefutable didactyl theropod tracks. Period. 

I believe I saw something on Paleoworld or some similar program of Zhi-Ming 
Dong in Alberta with Currie finding something that resembled two toed 
theropod tracks.  He interperated them as belonging to Troodon and had his 
hands with two fingers extended walk around over the trackway.

> There would have been no need to hold it aloft to reduce wear (the
> claws may have even been self-sharpening, like those of a cat, for
> all I know).

Self-sharpening cat claws?  I thought cats used couches to sharpen their 
claws....

>         Fourth, I do not know of any articulated theropod feet that show any
> evidence of a retracted claw.

I would think that any articulated sickle claw foot should show the exact 
opposite.  If the animal sat out and dried, rigor mortis should have the 
stronger larger calf flexing muscles pull the foot bones into hypoextension, 
not hyperextension.

>         I contend that the claw was for mating battles between males (I
> belive that Deinonychus has two distinct claw morphs; one with larger claws,
> see GSP's PDW), with a climbing role secondary. Ever been to a cock fight?

Perhaps, multiple uses are likely.

>         The skulls of dromaeosaurids were perfectly good for most
> carnivourous endeavours.

But the claws would have been so much more helpful in bringing down large 
prey.

>         Incedentally- the photos of the "fighting speciment" from Mongolia
> that I have seen show the feet of the Velociraptor a fair distance from the
> Protoceratops, but I would'nt trust this alone. Does the Protoceratops have
> any claw-slashed ribs? Just wondering. 

All the accounts I've heard say that one of the Velociraptor's feet is deep 
in the Protoceratops' belly.  Does anyone know either way?

Peter Buchholz
gpb6845@msu.oscs.montana.edu

Bacterial poop