Re: Pro(to)avis

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "Tim Williams" <twilliams_alpha@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Friday, September 16, 2005 10:50 AM
Subject: Re: Pro(to)avis


> Another question is whether pre-_Archaeopteryx_ ancestors of birds passed 
> through a four-winged ("tetrapteryx") gliding stage on the way to evolving 
> flight.


I would suggest that animals that had only a tip fan on their tails could be 
more likely than others to have hindlimb wings.  Animals that had a full 
tail (Archie) could be more likely to omit or minimise the hindlimb 
feathers.  It appears to me that the hindlimb feathers are likely derived to 
support the weight of the legs and long tail in those animals that have only 
tip fans, and that the tail carries that load in animals with full tails, so 
that there is no selective pressure toward hindlimb wings in full-tail 
animals.
JimC