Re: pterosaurs in trees...

[Nick Longrich <longrich@phoenix.Princeton.EDU>]

On the subject of paleognaths, there were a lot of small paleognaths
around in the Eocene filling various small land-bird niches.

Tracy points out that birds flap to get airborne, but you could just as
easily point to birds that launch themselves with a hop off a branch and
glide down to the ground. The reason why gliders need to flap is that they
are incapable of compensating for drag unless they lose altitude; flapping
produces thrust to compensate for drag and allows the animal to maintain
lift without losing height. There are not too many other ways to
gain/maintain altitude, there aren't many thermals in a forest, and
dynamic soaring isn't very practical outside a marine setting. To create
aviable flapping-first scenario, one still needs to point out what good
thrust will do without first having developed airfoils that can convert
forward motion into lift. It's sort of a helicopter vs. airplane thing-
thrust to provide forward motion for lift generation, or thrust as your
lift- the helicopter is far more expensive to operate than an airplane,
for what the analogy is worth. 
> 
> YES!!! Now someone else is on the right track! Like I said before, if 
> it was a good enought glider, why would it need to learn to flap?
> 
> Tracy
> 
> 
>