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Re: Pteros might be dinos?!? Oh no ...

Michael Mortimer <mickey_mortimer111@msn.com> wrote:
> Back in May, Dave Hone noted Bakker had mentioned
> pterosaurs could be descended from early dinosaurs

Bakker proposed this idea?  Oh well, it can't possibly be right then.

And before certain individuals on the DML jump all over me: I'm just kidding.  
Well, half-kidding.  ;-)

Erik Boehm <erikboehm07@yahoo.com> wrote:

> It would be easy to define a monophyletic "Dinosauria" that
> included Pterosaurs.
> Of course this would basically make Ornithodira=Dinosaria

I can't add much to what M. Mortimer said, except to reiterate that clades are 
defined by phylogeny (shared descent).  It's as simple as that.

In certain cases, clades are defined such that they 'self-destruct' if a 
certain taxon is included; but this has not been done for Dinosauria.  So if 
pterosaurs were found to have evolved from basal saurischians, then Pterosauria 
would be included within Dinosauria.  Just like birds are included within 
Dinosauria, because the bird clade (Aves) is nested inside Theropoda.

Under the 'pterosaurs-are-saurischians' scenario, Ornithodira would have the 
same content as Dinosauria - depending upon the position of _Scleromochlus_ 
(inside or outside Saurischia), and whether or not you define Ornithodira such 
that it must include _Scleromochlus_ (Sereno, 1991). 

But we're getting way ahead of ourselves.  These are just hypotheticals, and no 
phylogenetic analysis has as yet recovered Pterosauria nested inside