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Re: Archosaur Origins (& the Clade Cemetery)

-----Original Message-----
From: Ken Kinman <kinman@hotmail.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Thursday, August 23, 2001 2:57 PM
Subject: RE: Archosaur Origins (& the Clade Cemetery)

>     Sereno in his 1991 paper on Basal Archosaurs states:
>     "Definition---Ornithodira includes Pterosauria, Scleromochlus,
>Dinosauromorpha (including birds), and all descendants of their common
>      Therefore, I don't use the term ornithodirans any more.
>Archosauromorphs suits me just fine, and the thought of changing to a much
>more inclusive Ornithodira or cutting pterosaurs out of it----well, it
>be a confusing mess.  If Dave is right about pterosaurs being
>prolacertiforms, then Ornithodira should be abandoned.
>      The characters that were offer as synapomorphies of Ornithodira were
>apparently not synapomorphies at all.  Ornithodira appears to be dead or
>dying, and hopefully PhyloCoders will not try to redefine it.  Time to move
>on.  I think there is a nice plot in the Clade Cemetery for "Ornithotarsi"
>as well.

Where does that leave archosauromorphs then?? According to Dave Peters,
pterosaurs weren`t even archosauromorphs. The characteristics of preorbital
fenestra and advanced mesotarsal ankle are just convergences. I always
assumed these characters were strong definitions of the group "Archosaur".
Do we now eliminate these characters as synapomorphies of this major group?

Also,...is Ornithodira dead without a fight? I assumed there would be some
kind of rebuttal to Dave`s phylogeny. Aren`t there still some (Padian?) that
still think lagosuchids and pterosaurs are closely related?....I must point
out that I`m not exactly taking sides here as I believe they are both
partially right. In my own point of view, I see pterosaurs as being
descendants of prolacertiformes, and at the same time, lagosuchids being
secondarilly flightless (glideless?) descendants of pterosaur forms.