Re: bauplan convergence

[Stanley Friesen <sarima@friesen.net>]

At 02:25 AM 6/17/00 -0700, Scott Hartman wrote:
> > > Gravity can get ANYBODY to the ground that leaps out of a tree.
>
> > > Gravity, air, and a little extra skin on the arms gets you >>parachuting.
>
> > > But parachuting doesn't require that you flap.
>
>     Actually, while the term "parachuting" is bandied about by many when 
> discussing incipient levels of gliding, this usage is 
> innappropriate.  Balda et al. (1984 Archaeopteryx conference 
> volume)provide a more aerodynamically correct definition of parachuting 
> as a method to slow descent using only drag (or at least where lift is 
> negligable).  Animals that can glide at a measly 45 degree angle from the 
> horizontal are still creating lift at an impressive 70% of body 
> mass.  Few, if any animals qualify as parachuters (although perhaps 
> flying frogs are an exception?)  That's why flying squirrells and snakes 
> have flat bottoms but round(er) tops.

I am aware of the difference.  I was thinking that drag-based reduction of 
fall rates might precede the more specific adaptations establishing lift 
surfaces.

--------------
May the peace of God be with you.         sarima@ix.netcom.com