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




David Marjanovic wrote:

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...

For the purposes of drag, I'm not so sure the precise orientation is important.


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).

To put the Pouncing Proavis hypothesis in it historical context, it was proposed at a time when _Caudipteryx_ was thought to be very close to the origin of birds. Now, we have _Microraptor_ and possibly _Pedopenna_, both of which are closer to the base of the Aves than either _Protarchaeopteryx_ and _Caudipteryx_ (both of which are falling out as basal oviraptorosaurs). Microraptorans and _Pedopenna_ offer alternate ecomorphologies for pro-avians. Then again, these four-winged gliders may have been an evolutionary dead-end and are just muddying the waters when it comes to reconstructing the origin of avian flight.


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 think this is a slight oversimplification. The 'pounce' may get the Proavis close to the prey, and it could run over the intervening distance with those cursorial hindlimbs.


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

Swimming, a la Ebel's swimming-to-flight hypothesis? It's an interesting model... but, nah, don't think so. :-)


Cheers

Tim