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Re: Pre-archosaur...was : What came before Eoraptor?



-----Original Message-----
From: Chris Bennett <cbennett@bridgeport.edu>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Monday, April 10, 2000 10:07 AM
Subject: Re: Pre-archosaur...was : What came before Eoraptor?


>
>In my 1996(?)  paper on the phylogenetic position of the Pterosauria, I
>argued that the phylogenetic position of the Pterosauria depends on the
>interpretation of a suite of hindlimb characters.  If they are interpreted
>as synapomorphies with the Dinosauria, then the Pterosauria is the major
>sister group of the Dinosauria.  However, if the suite of characters are
not
>shared with the Dinosauria, then the Pterosauria are much further down the
>cladogram.  In my analysis (assuming those characters were homoplasic
rather
>that homologous) the Pterosauria came out as the sister group of
>Erythrosuchia + everything else up the cladogram.  I noted in that paper
>that if that cladogram was correct, then the Ornithodira as defined by
>Sereno would be much more inclusive than he intended.  David Peters
>presumably either noted my comment or came to the same conclusion
>independently.
>

I see now. Then Dave Peters is stating that the advanced mesotarsal ankle
arose on two separate occasions.

Couldn`t there be an alternative path, like: prolacertilian to pterosaur to
lagosuchian (secondarilly flightless) to dinosaur?

Or even what I propose, the more radical prolacertilian to pterosaur to
avian to various secondarilly flightless theropod groups?