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RE: Do we have dromaeosaurid evolution backward?
Hopp and Orsen do actually argue that their hypothesis can help explain the
aerodynamic aspect, as the narrower "leading" edge of the vanes is more
conducive to tight folding, rather than just to aeroplaning the wing planform.
This would then go hand in hand with wings that tend to be tightly folded,
rather than just forming "wings" and gliding surfaces. Those then become
exaptations. It may progress from a brooding "wing," running aerofoils, WAIR
aerofoils, parachuting -> gliding aerofoils, which would then force the wing to
develop "braking" mechanisms such as the alula to assist in retarding stall.
Wing planform control can exist very early on in the evolution of the
structure, and need not ever involve the development of flight.
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
> Date: Thu, 25 Aug 2011 15:28:23 +1000
> From: email@example.com
> To: firstname.lastname@example.org
> Subject: Re: Do we have dromaeosaurid evolution backward?
> David Marjanovic <email@example.com> wrote:
> >> As I see it, one major problem with this idea is that if large,
> >> pennaceous feathers originally evolved for aerodynamic purposes,
> >> these feathers are unlikely to have arisen in "large" (2-4m long)
> >> theropods that used their forelimbs for catching prey.
> > I suppose that's where Hopp & Orsen (1998) come in.
> Using the forelimbs to help incubate eggs might explain the presence
> of big pennaceous feathers. But it doesn't explain why those feathers
> would be aerodynamic. Or else, this step (bipinnate, aerodynamic
> vanes) arose at least twice.