Re: Did dinosaur wings evolve for breeding display?

[dinoboygraphics@aol.com]

Mark Hallet wrote: "If wings evolved primarily as a display device for 
visual enhancement in breeding, why do we see already functional 
aerodynamic structuring (i.e., unequal vane proportions) in the wing 
feathers of known flying dromaeosaurs?<<

And Roberto Takata responded: "What is the phylogenetic position of 
Caudipteryx? A secondarily flightless oviraptorosauria?"

As I've pointed out before "aerodynamic" is not synonymous with 
"flight" or "gliding".  The spoilers in race cars are aerodynamic.  
Reducing drag is as well.  Most robust phylogenetic studies recover 
oviraptors sufficiently known fliers that it appears unlikely that they 
are secondarily flightless (even if deinonychosaurs...which I doubt).

A large problem with the whole discussion is the very concept of "wing" 
here.  We know of coelurosaurs with elongated but non-branching 
filaments on their arms, we know of coelurosaurs with apparently 
branching but aren't true remiges, we know of basal maniraptorans with 
non-assymetrical remiges, and several species for which their are 
assymetrical remiges but legitimate debates about their flight ability 
(and/or lack thereof).  Finally there is a large and very succesful 
group of flying maniraptorans that bear assymetrical remiges.

Which ones are the "wings" we are talking about?

If the origin of "wings" involves elongation of filaments it seems 
perfectly reasonable to think that sexual selection was involved.  If 
the question is how do we get from unbranching to branching filaments, 
it's plausible but seems less likely that sexual selection was the 
culprit.  If the origin of "wings" pertains to the derivation of 
remiges from more simple branching filaments, it seems unlikely that 
this happened outside of selection that involved aerodynamics (thought 
not necessarily gliding or flight), and in the case of assymetrical 
remiges it's almost beyond dispute that aerodynamic forces rather than 
mate selection were the driving force (but conceivably still not 
flight).

Of course, all of these things happened before you get to an 
Archaeopteryx-grade maniraptoran, yet there are so many important 
changes to the manus, to inboard feather distribution, to pectoral 
girdle and glenoid morphology, and to alular evolution that you could 
be forgiven for asking how the avian wing evolved after the 
Archaeopteryx stage of avialan evolution, and breeding display was 
probably at most a minor factor here.

Sorry to make this complex, but like Einstein said: "Make things as 
simple as possible, but not more."  Over-simplification obfuscates the 
actual issues.


Scott


Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

-----Original Message-----
From: Roberto Takata <rmtakata@gmail.com>
To: marksabercat@yahoo.com
Cc: david.marjanovic@gmx.at; dinosaur@usc.edu
Sent: Wed, 15 Apr 2009 2:28 pm
Subject: Re: Did dinosaur wings evolve for breeding display?






On Wed, Apr 15, 2009 at 4:17 PM, Mark Hallett <marksabercat@yahoo.com> 
wrote:




[]s,

Roberto Takata