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



----- 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...