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RE: Evidence For a Feathered Velociraptor...



Hey Don, the idea of spiny maniraptoran forearms reminds me of a discussion
we had here a while ago:

http://dml.cmnh.org/2005Dec/msg00147.html

'Mantis lizard', anyone?

 
-----------------------------------------------
Dr John D. Scanlon, FCD
Palaeontologist, 
Riversleigh Fossil Centre, Outback at Isa
19 Marian Street / PO Box 1094
Mount Isa  QLD  4825
AUSTRALIA
Ph:   07 4749 1555
Fax: 07 4743 6296
Email: riversleigh@outbackatisa.com.au
http://tinyurl.com/f2rby


> -----Original Message-----
> From: don ohmes [mailto:d_ohmes@yahoo.com]
> Sent: Wednesday, September 26, 2007 8:57 PM
> To: dinosaur@usc.edu
> Subject: Re: Evidence For a Feathered Velociraptor...
> 
> Er, I think Tim is correct in that load is load, and whether it is
> aerodynamic load or grasping thorns or whatever that is the load of
> origin, it works. What is most probable is debatable, and as usual I lean
> firmly to the side of "yes".
> 
> Keeping in mind that I haven't followed this as closely as I should before
> commenting --
> 
> One thing interests me that I haven't noticed being mentioned; if I
> understand the function of "quill knobs" correctly, that function implies
> stiffness of feather, which in turn implies that feather stiffness came
> first. So, ignoring momentarily the aero/thermal/display scenarios for
> feather stiffness; could it be that quill knobs are actually 'spine
> knobs', spines being useful in all the predation/combat scenarios
> mentioned? Is preservation good enough in the fossils mentioned to rule
> spines out?
> 
> Don
> 
> ----- Original Message ----
> From: Tim Williams <twilliams_alpha@hotmail.com>
> To: dinosaur@usc.edu; oak@uniserve.com; twilliams_alpha@hotmail.com
> Sent: Tuesday, September 25, 2007 11:08:42 PM
> Subject: RE: Evidence For a Feathered Velociraptor...
> 
> 
> Graydon wrote:
> 
> >> I can understand why quill knobs imply structured feathers, but not
> >> aerodynamic load.
> >
> > Because that's what quill knobs _do_,
> 
> 
> Well, that's what quill knobs do in _modern_ birds.  But, as with many
> avian/avialan characters, the reason why quill knobs first
> evolved may not be the same reason as why modern flying birds have quill
> knobs.  Exaptation, in so many words.
> 
> 
> What I'm saying is that there may be other explanations beside
> 'aerodynamic load' as to why _Velociraptor_ has quill knobs.
> I'm not arguing that the quill knobs have _no_ function in _Velociraptor_;
> I'm merely arguing that the function of quill knobs in
> _Velociraptor_ may not be associated with aerial locomotion.  If the
> latter is true, this non-aerodynamic function may have been
> the original function of quill knobs, which were later exapted toward
> aerodynamic load in the line leading to birds.
> 
> 
> > If the feathers are being flapped through the air, at speed, for
> > whatever reason, they're going to be under aerodynamic load. It doesn't
> > matter if it's leaping to claw something's face off or fanning the nest.
> 
> 
> Yep, fair enough.
> 
> 
> > That only works if there _were_ such tussles, and I don't think there
> > were. It's a bad idea to wrestle if your advantages are being fast and
> > spiky and you're smaller than your prey animal.
> 
> 
> And yet, one _Velociraptor_ skeleton was preserved locked in a deadly
> embrace with a _Protoceratops_ skeleton.  So this
> particular tussle is more than just hypothetical.
> 
> 
> Carpenter, K. (2001).  Evidence of predatory behavior by carnivorous
> dinosaurs.  Gaia 15: 135-144.
> 
> 
> Although other interpretations have come up for this pose (e.g., the
> _Velociraptor_ was scavenging a _Protoceratops_ carcass;
> the _Protoceratops_ was the aggressor), the most plausible explanation is
> that the _Velociraptor_ was attacking the
> _Protoceratops_, and used its forelimbs (as well as its hindlimbs) to
> engage its prey.
> 
> 
> > But I don't think it _is_ a correlation between quill knobs and powered
> > flight. I think it's a correlation between quill knobs and aerodynamic
> > load on retrices.
> 
> 
> 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.  The need to hold the
> feathers in place during tussles with prey (especially large prey) is one
> possibility.  BTW, the two factors (aerodynamic load &
> predation) are not at all mutually exclusive.  I'm not saying you're
> wrong.  I'm just saying that other factors beside
> aerodynamic load deserve consideration.
> 
> 
> > We know there are other ways to deal with feather control and anchoring,
> > because there are modern volant species as don't have quill knobs, but
> > the presence is pretty tightly correlated with keeping anchored against
> > airflow.
> 
> 
> Yes, but no modern bird uses its forelimbs as specialized instruments to
> grasp or kill prey.  Not like _Velocir
> he quill knobs are expensive, and we know that other linages of
> > velociraptorin theropods lost them, so some sort of developmental lock
> > isn't the least hypothesis; the least hypothesis is that they were used
> > to support retrices under aerodynamic load.
> 
> 
> For sure.  (Although I think you mean 'remiges' rather than 'rectrices'.
> I don't mean to be pedantic, but the tail feathers are a
> whole other box and dice!)  I don't believe in a developmental lock either
> - not for quill knobs, anyway.
> 
> 
> > I can tell that you, personally, have not been assaulted by geese. :)
> 
> 
> Nor me.  Just a bad-tempered emu.  And a few overprotective magpies during
> nesting season.
> 
> 
> > My personal guesses are intraspecies competition for leap height, and
> > predation advantage by assisted leaping out of the plane of the ground.
> >
> > No idea how to test any of that, and as you say, highly speculative.
> 
> 
> Nothing wrong with that!
> 
> 
> Cheers
> 
> Tim
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