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Re: Re: Drepanosauridae

>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.

In the recent review of Megalancosaurus in JVP, I believe the author(s)
suggested that the "antoribital fenestra" may be part of a whopping big
external naris.  That sounds strange to me, but then again, most aspects of
the critter are weired!

I cannot recall the presence of an antorbital fenestra outside of
"traditional" Archosauria (=Archosauria, Euparkeria, Erythrosuchidae, etc.)

>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?

Yeah, I'm kind of puzzled by the rhynchosaurs and prolacertians in there,
too.  I can't recall where champsosaurs are these days (I think they are
also archosauromorphs).  The Sphenodontia is pretty well established as a
lepidosaur clade, and includes some aquatic members!

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661