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RE: ADV: RE: Evidence For a Feathered Velociraptor...



Graydon wrote:

> I'm not talking about flight loads, just 'forces exerted by air'.


But I'm not even talking about 'forces exerted by air'.  I'm just talking about 
forces in general - such as that generated by struggling prey held in a
 _Velociraptor_'s grasp.


> Can you think of a substantial load on a feather that isn't aerodynamic?
> (in the 'forces exerted by motion through air' sense.)


I don't know about "load".  I just meant stresses or forces in general.


> Urm... I think I see the difficulty.
>
> Aerodynamic load has (as I'm using it) nothing to do with flying. It
> has to do with forces exerted by moving the feather through the air.
>
> Given remiges, there would be aerodynamic forces acting on them. Given
> the quill knobs, we can postulate substantial aerodynamic forces, but I
> am not hypothesizing about what generated those forces, only that they
> were present.


No.  Given only quill knobs we canNOT postulate aerodynamic forces for 
_Velociraptor_ with 100% confidence.  This is an assumption on your part.  All 
we 
can say with reasonable confidence is that the quill knobs are there in 
_Velociraptor_ to reinforce the attachment of the remiges to the forearm.  
Anything 
else is speculation - such as exact function.  It may have nothing to do with 
aerodynamic load, or any 'forces exerted by air'.  Then again, the quill knobs 
might indeed have something to do with aerodynamic load - this is certainly the 
case with modern birds.  But we cannot _assume_ this holds for 
_Velociraptor_.


I understand what you're saying.  Whether the forelimbs were used in gliding, 
leaping, fanning nests, mating rituals, predatory motions, waving goodbye... 
whatever.... all these behaviors involve 'forces exerted by air'.  But the 
quill knobs might not be there for any of these reasons in _Velociraptor_.  The 
quill 
knobs might be there for a reason that had nothing to do with 
aerial/aerodynamic behaviors.  The more secure attachment of the remiges to the 
forearm 
implied by quill knobs could simply be associated with the stresses the remiges 
were exposed to when the predator was subduing prey with the aid of the 
forelimbs.  That's all.


> That's one arm caught in the beak, though, and one foot stuck in the
> throat, and I take that example as the _Velociraptor_ having plain
> honest lost.
>
> That's not an example of a cling-and-bite or hook-and-claw strategy;
> that's either (depending on order of events) a failed predation attempt
> because the _Protoceratops_ didn't die fast enough to prevent it from
> killing its attacker or a desperate attempt by the _Velociraptor_ to get
> free after an aggressive defence resulted in the bit arm.


Doesn't matter.  In all of your scenarios the _Velocraptor_ was the aggressor.  
No offense, but the idea that _Velociraptor_ did NOT use its arms and hands 
in prey capture seems to me to be plainly ridiculous.  I mean, have you seen 
those guns?


>> I would go a little further and say it's a correlation between quill
>> knobs and the need to securely hold the remiges in place. That is,
>> aerodynamic load is one possible force that acts against the remiges;
>> but there could be others.
>
> There could, but I'm having a heck of a time coming up with any.

I mentioned one several times: predation involving the forelimbs.  I'm 
astonished this strategy is so hard to swallow for _Velociraptor_.  It's hardly 
revolutionary.  Theropods were using the forelimbs to grasp and kill prey since 
they were knee-high to a prosauropod.


> Tussles with prey would not produce a plucking moment, though; the
> geometry for that doesn't work out. And if there's a general plucking
> moment involved in prey interactions, what makes remiges special? Why
> is not the entire velociraptor denuded of its feathers?

I'm not really referring to 'plucking' in particular.  I just mean having the 
remiges attached in a more secure fashion (i.e., as conferred by quill knobs) 
would 
help the remiges resist the wear and tear of everyday life as an aggressive 
predator.  A predator, I might add, in which the forelimbs played a lively (and 
deadly) role in predation.


> True, but the mechanisms available to _Velociraptor_ (and relatives) are
> very similarly anatomically constrained; arguably more constrained, in
> terms of forelimb motions.


Or, the forelimbs were specialized to grab large prey with both hands.  This is 
what Gishlick's biomechanical study was driving at for _Deinonychus_.  


> I have been assaulted by geese; also ducks, and threatened by swans.
> (Redwinged black birds, so far as nesting season goes. :)

Have you ever appeared in a Hitchcock movie?  ;-)


Michael Lovejoy wrote:


> Can I ask again, how do we know Velociraptor used it's forelimbs to grasp or 
> kill prey? I know you cited the famous 'Fighting Dinosaurs' specimen, but 
> it's 
> pretty clear that whatever that particular Velociraptor was doing, it wasn't 
> working out too well...


Well, they were both killed by a sandstorm.  Until that point it's hard to know 
who had the upper hand (or claws, or beak).  But it doesn't matter; the 
important point is that _Velociraptor_'s forelimbs appear to be actively 
engaged in predation.  Plus there's Gishlick's work on _Deinonychus_ (see 
above).\



Cheers


Tim
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