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Re: Which is Cosesaurus?



On Wed, 7 Jun 2000, Larry Febo wrote:

> Well,...I contacted Dave Peters soon after I made that last post, to make
> sure I wasn`t misrepresenting him. Since he hasn`t responded to the list, I
> feel I must mention that in fact he does NOT consider any of the
> prolacertilians as Ornithodiran! (So I guess you had better not call that
> phylogeny "Dave Peters" ). He also said that Cosesaurus has a mesotarsal
> ankle, but that it evolved independantly of the dinosaurs. ( I am assuming
> he dosen`t consider pterosaurs ornithodiran either, or rejects the term
> ornithodiran,....but here I may again be misrepresenting him......I sure
> would like to see his paper on the subject if it is ever published!).

Dave Peters doesn't appear to use the taxon Ornithodira on his site,
AFAICT. But if you couple his phylogeny with the definition of Ornithodira
as the most recent common ancestor of pterosaurs and dinosaurs, plus all
of its descendants (which is the only definition I am aware of), then not
only is Prolacertiformes (and other Pterosauromorpha) included, but also
Proterosuchidae, Erythrosuchidae, Proterochampsidae, Parasuchia, Suchia,
and Ornithosuchidae. Basically, Archosauriformes becomes a subclade of
Ornithodira, instead of the other way around.

Given that this composition is so different from the usual make-up of
Ornithodira, I would guess he simply abandoned the clade.

Incidentally, under his phylogeny, Archosauriformes is also a sub-clade of
Dinosauromorpha (Dinosauria <-- Pterosauria). Also, he appears to have
Archosauria marked at the wrong clade. Since the definition is 
(Crocodylia + Neornithes), it should be at the node where Suchia branches
off, not _Euparkeria_.

-- T. Michael Keesey .................................. <tmk@dinosauricon.com>
   My Worlds (including The Dinosauricon) ... <http://dinosauricon.com/keesey>
   AOL Instant Messenger ........................................ <Ric Blayze>