[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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

-- On Fri, 9/26/08, David Marjanovic <david.marjanovic@gmx.at> wrote:

> No. None shows any hint of a transition from gliding to
> flapping.

Perceived difficulties relative to the transition from gliding to flapping 
probably birthed the "ground-up" movement :D.

Maybe it isn't as hard as I used to think, however.

> Some have doubted whether such a transition is even
> possible, arguing that 
> incipient flapping would lose to an increase in drag and
> decrease in lift in 
> a glider. 

Braking maneuvers such as those performed by flying squirrels on 'landing 
approach' involve (afaik) simultaneous movements of out-stretched forelimbs 
where force is directed ventrally. Rapid repetition of these maneuvers seem to 
arise naturally, whether for adjusting body orientation in preparation for 
landing, or making fine adjustments to speed. 

Logically, selection can act upon this most minimal 'flapping' behavior in 
certain other circumstances. 

In my opinion, two scenarios are: 1) in a 'pre-powered flight' environment, 
dominated by gliders, repeated power dives (and subsequent pullouts) could 
convey advantage to predator and prey alike, assuming both are gliders. 2) 
where glide length might convey tactical advantage to a predator, such as a 
bipedal perch-hunter in an open or semi-open environment, gliding down on a 
terrestrial prey could culminate in a running/flapping style of pursuit (again, 
in a pre-power world). 

This last would be the lifestyle of Arch. immediate ancestors, in my personal