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Re: Drepanosauridae



In a message dated 95-12-11 13:45:33 EST, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

>Actually, the Drepanosauridae were archosauroMORPHs, but well outside the
>clade Archosauria (=crocs & birds and their most common ancestor).  They
were
>further from true archosaurs than are the proterosuchids, Euparkeria,
>Erythrosuchidae, etc.
>
>

This is the part that's giving me the trouble. The skull of
_Megalancosaurus_, which is the only drepanosaurid skull known, has numerous
archosaurian characters, the most interesting of which is a gaping antorbital
fenestra. I'll buy that drepanosaurids are non-archosaurian if it can be
established that the antorbital fenestra is plesiomorphic for the clade. Of
course, it is almost certainly non-archosaurian if the crown-group definition
of Archosauria is used, namely, Archosauria = most recent common ancestor of
Crocodylia and Aves plus all its descendants.

I'm also musing about stretching the clade Archosauromorpha back to include
rhynchosaurs and prolacertians--something that I've seen advocated in a
couple of recent papers. These would then fall into the stem-group
Archosauromorpha = Archosauria + all diapsids more closely related to
archosaurs than to extant lepidosaurs. By the way, where do _Sphenodon_ and
champsosaurs fit in this mess?

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