VALIDITY OF AVES

["Matthew Troutman" <m_troutman@hotmail.com>]

<<With recent discoveries and discussion of avian dinosaurs,
flightlessness,etc, our widened conception of dinosaurs to include 
birds, is it not time to re-define "birdness" ?>>

No...

<<Is Aves still valid ?>>

Yes.

<<Is it a polyphyletic grouping resulting from different birdlike 
dinosaur ancestors?>>

No.

<<Do birds have a common ancester?>>

Yes.  The common ancestor is _Archaeopteryx_.  No matter which basal 
avian phylogeny that you read (whether it supports Sauriurae or 
Ornithothoraces) they all stick by the conclusion that _Archaeopteryx_ 
is the closest thing to an avian common ancestor.  Other possible birds 
(_Unenlagia_) which may be more "primitive" than _Archaeopteryx_ are 
simply too fragmentary to make a detailed case for their position in 
Aves.  

<<Are ratites, and kiwis actually birds at all?>>

Let me direct you to Witmer (1991) and Feduccia (1996); previous 
arguments against the "birdiness" of these animals have been refuted.  

Anyway, all analyses prove that ratites came from avian ancestors.  
Lithornithids have been showed by Houde (1988) to be the ancestors of 
ratites.  

I'll give a more complete argument later. 

Matt Troutman

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com