Re: Third claw for climbing was Re: Pro(to)avis

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Tim Williams" <twilliams_alpha@hotmail.com>
Sent: Saturday, September 17, 2005 3:53 AM

> In the earlier stages of the evolution of avian flight, the hindwings, the
> forewings and the feathered tail may have worked together to maximize 
> DRAG,
> rather than lift.  This means that the neither the fore- or hindwings 
> needed
> to be held subhorizontally during aerial locomotion.

Again this depends on the orientation of the feathers. If they are all in 
parasagittal planes, there isn't going to be much of an effect...

But I've never liked the Pouncing Proavis idea, for other reasons. It 
requires a rather small animal (if it's too heavy, feathered fringes won't 
have enough of an effect). It also requires a rather large vertical distance 
in relation to the size of the animal (if the leap is too short, there's no 
need to use any aerodynamics, as opposed to steering by means of the way the 
animal jumps off). Then it requires pretty large prey, because small prey is 
unlikely to stand still (within a sufficiently small area at least) for long 
enough that an incipient Pouncing Proavis would have any chance.
       It goes without saying that someone needs to quantify this. _If_ it 
comes out that the model requires, say, that something the size of a weasel 
must jump off from a height of 3 m to catch something the size of a pig, 
I'll consider the model disproven...

I prefer separate explanations. Wings for brooding, then exapted for... who 
knows... WAIR or maybe even swimming or...