RE: Evidence For a Feathered Velociraptor...

[Tim Williams <twilliams_alpha@hotmail.com>]

Graydon wrote:


> Quill knobs imply substantial aerodynamic load and structured feathers,


I can understand why quill knobs imply structured feathers, but not aerodynamic 
load.  At least not for 
_Velociraptor_.  Sure, the forelimb feathers might have been exposed to certain 
aerodynamic forces, such as 
when rapidly extended or retracted during a predatory strike; or (even more 
dramatically) if _Velociraptor_ 
was leaping through the air toward large prey.  But it's a tough sell to say 
that these forces qualify as 
"aerodynamic load". (I'm not suggesting that you are saying this, BTW; I'm 
justing setting the scene.) 

 
The presence of quill knobs means that the feathers were anchored to the ulna 
with ligaments.  The selective 
pressure that originally drove the evolution of quill knobs might indeed have 
been aerodynamic load, such as 
WAIR, or phugoid gliding, or primary thrust generation, or whatever.  But for 
_Velociraptor_ (and maybe 
_Rahonavis_ too) quill knobs may have evolved (or been retained) for a 
non-aerodynamic reason.  For 
example, having the feathers more tightly anchored to the ulna would help them 
stay attached during 
predatory tussles with large prey.  Because _Velociraptor_ has broken the 
correlation between quill knobs and 
powered flight, we have to come up with other (non-aerodynamic?) explanations 
for why flightless 
maniraptorans might have had quill knobs.  Or else, it could be argued that the 
quill knobs of 
_Velociraptor_ are just remnants of an ancestry from maniraptorans which were 
aerodynamic (and maybe 
powered fliers).


> So at least one of:
> 1 these are a big help in catching up to the prey before subduing it
>
> 2 these are absolutely required to have a shot at successful
> breeding (display leaping, tucked-wrist feather-battering fights for
> breeding rights, fanning the nest, who knows...)
>
> 3 if you don't have these, you can't get away from your larger
> theropod relatives
>
> has to be true, along with "these don't make it more difficult to subdue
> prey".
 

You know, I'm coming around to your way of thinking.  In support of your 
argument, Gishlick (in the Ostrom
Symposium volume) noted that feathers on the hands would not have intefered too 
much with predation, 
because the feathers were attached roughly perpendicular to the claws, and 
oriented tangentially to the 
prey.  He also suggested that large forelimb feathers might have advantages in 
predation - they could cause 
the hands and arms to seem larger (and prevent small prey from dodging to 
either side); or for pack-hunters 
this same ploy could be used to "herd" prey.  Of course, both ideas are highly 
speculative.  They would 
certainly make for interesting illustrations.

 
Cheers
 
Tim

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