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Re: Velociraptor footprints



        First off, I'm not denying that dromaeosaurs/troodontids >could<
hyperextend their second digits. To the contrary, the hyperextendable claw
would have been well employed as a weapon and as a ritual intimidation display. 

At 03:10 PM 7/25/97 -0400, Nick Longrich wrote:
>> Extant ratites, that have been known to kill even humans with their inner
>> digit's claw, do fine without carrying their second digit off the ground. 
>       The cassowary digit is not, as far as I know, exactly comparable.
>For one, it doesn't look as if it had the ability to hyperextend as in
>dromaeosaurs (I can check up on this one). 

        That much is certain.

Dromaeosaurs could hyperextend
>their second pedal digits and logically must have done so frequently.
>Also, the cassowary's large claw is not the thin, bladelike structure of
>a dromaeosaur, and cassowaries don't have a shortened second metatarsal
>and more-or-less equal metatarsals III and IV. So the comparison may only
>go so far.  

        Although morphologically differing, the postulated function of the
dromaeosaur claw and the observed function of the ratite claw make for good
analogues. 

[snip] 
>       The absence of these prints is really puzzling, but until the past
>few years, if you asked someone where all the pterosaur footprints were
>they would have been forced to shrug their shoulders. 
[snip]
 So the absence of these didactyl prints should not necessarily be
>taken as a huge problem. In fact, we could just as easily take the
>argument the other way and say, "well, if the toes were on the ground,
>where are the prints with enormous imprints of bladelike second toe
>claws?" Either way, we're still lacking dromaeosaur prints, it seems, they
>should be pretty distinctive regardless of whether they held the claw up
>and ran on the other two digits (as the skeleton certainly appears capable
>of doing) or held it down. 

        Hold on, Nick, I'm getting to that?

At 09:40 PM 7/25/97 EDT, Judy Molnar wrote:
>Extant ratites have blunt toe claws, not a sharp, curved claw like a
>dromaeosaur.  And as I understand it, it is the force of the whole foot's
>blow that does the damage, not the claw by itself.

        Well, the ratite's claw is probably blunter than that of the
dromaeosaur, but still sharp enough to do some fairly precise butchering in
defensive behavior.

 [snip]
>> Occam's Razor 
>>tells us
>>that small theropods simply didn't carry their second digits off the 
>>ground.
>
>>From the trackways so far seen, this is true.  This just doesn't seem
>settled by the evidence in either direction, except the skeleton has that
>darn sickle claw on the foot.  Sure is a head scratcher.  What if the
>sickle-claws avoided soft substrates and never got their tootsies
>preserved?

        Again, old man Occam says "no." In fact, the long toes of
dromaeosaurs/troodontids seem to be well suited to traversing soft
substrates. Probably good swimmers, too.

At 10:05 PM 7/25/97 -0400, Dinogeorge wrote:
>Nor do I recall--but I'm no trackway expert--any trackways that show small
>theropod footprints in which digit II has an enlarged claw. There is simply
>no trackway evidence either way about how dromaeosaurids may have held their
>second pedal digits.

        Well, I think dromaeosaur tracks may have been found. The early
Cretaceous Gething Group in British Columbia was deposited at the same time
as the Cloverly Formation in the American midwest. I know that Ken
Carpenter, a few years back, correlated several Gething tracks
(Tetrapodosaurus) to the skeleton of the coeval Sauropelta from the
Cloverly. Now there is a certain ichnospecies of small theropod from the
Gething (I'll have to crack open my files for the sp. name) that seems to
match Deinonychus antirrhopus' pedal skeleton >perfectly< in size and
proportion. The toes are all of the right length and everything. However,
the toe claw on the second digit left only an ambiguous trace (just as all
of the other claws did). This can be expected, especially with blade-like
claws. In 99% of all substrates, the imprints of the claws on >any< animal
will be obliterated by suction, deformation, and any number of other
processes as the foot is removed from the substrate. Only in a very rare few
substrates, like a firm clay, would a good claw impression be preserved. The
Gething tracks are not in any such substrate (unfortunately), so good
preservation of toe claw imprints is unlikely.

Sam