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Re: Did dinosaur wings evolve for breeding display?



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