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RE: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

> > It is not too surprising that there are no gliders
> currently making the transition to powered flight, 
> > considering the fact that they would have to invade
> niches occupied by birds and/or bats as they did so. 
> > Seems a lot to ask...
> It sure is.  However, I'm setting the bar much lower. 
> I'm not asking that gliders have to make the transition
> to powered flight.  All I'm pointing out is that no
> glider that I know of (not amphibian, reptile, mammal) shows
> the slightest interest in flapping their arms.  If flapping
> confers advantages to a glider, why is this the case?

No extant glider is exapted to flapping flight like a "dino-bird" would have 
been. Femoral articulation adapted to gliding is not especially helpful when it 
comes to flapping, except for a hypothetical "true" (4-winged flapping) 
"Tetrapteryx" (which would face an entirely different set of problems after 
landing, presumably).

Basic gliding ability is rather easy to achieve for vertebrates. Basic flapping 
flight requires more anatomical conditions to be right. So I would not be 
surprised if a glider evolved into a flapper - as long as it was not *too* much 
of a glider that is. The other way - from flapping back to gliding, or actually 
soaring (which is similar but not identical) - happened again and again. In any 
case, I would also not be surprised if a gliding *theropod* evolved towards 
flapping flight. If not those, which vertebrate could do it?

Among vertebrates, the more of a climber you are, the less likely it is that 
you evolve into a flapper. If, OTOH, you have a bauplan like Archie did, odds 
are that gliding will be something that is being played around with ever so 
often and that's gonna help you a lot in the beginning, but also that the 
anatomy will eventually be put to use for gaining full flapping flight. Even if 
Archie could only achieve the beta version of a half-wingstroke, its 
exaptations were too good to miss.



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