Re: Archaeopteryx and Flight

[Stan Friesen <swf@ElSegundoCA.ATTGIS.COM>]

>From: NEIL CLARK <NCLARK@museum.gla.ac.uk>
 > 
 > Why?  Why should there have been any evolutionary pressure to 
 > develop flight at all? 

Well, to start with, flight is metabolically expensive.
So expensive that it is often *lost* in island species.

 > Within the range of intraspecific variation, there 
 > may have been an extreme morph that allowed for flight.  Due to the 
 > lack of competition in this area, the morph was able to alienate itself 
 > further from the non-flighted morphs especially after the demise of the 
 > pterosaurs. 

Pterosaurs did not start to decline until *after* birds evolved.
In fact it is reasonable to conclude that it was competition with
birds that gradually eliminated most pterosaur groups.
[The last pterosaur groups, in the Late Cretaceous, were very
specialized, and invariably large - all of the small, generalized
insectivorous types had died out by then].


swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.