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Date: Sat, 13 Aug 2005 00:52:08 +0200
From: David Marjanovic <david.marjanovic@gmx.at>
To: DML <dinosaur@usc.edu>
Cc: PML <phylocode@ouvaxa.cats.ohiou.edu>
Subject: Re: Aliwalia [from Adam Yates]
(Sorry for the cross-posting. Info for the PhyloCode mailing list:
- If you're pressed for time, please jump to the last paragraph.
- According to a new, unpublished analysis, the traditional Prosauropoda is
turned into a long list of successive outgroups to Sauropoda. Prosauropoda
has a stem-based definition with *Plateosaurus* as the internal specifier;
its sistergroup is Sauropoda, which used to consist of animals like the
*Brachiosaurus* shown in Jurassic Park; Sauropodomorpha is a stem-based
clade that includes both; against all expectations, *Plateosaurus* has
turned out to be among the most basal sauropodomorphs -- all previous
suggestions of prosauropod paraphyly had it rather close to the traditional
contents of Sauropoda.)
> >Interesting that massospondylids, Yunnanosaurus and 'riojasaurids' have
> >been moved to basal sauropod status in Yates' latest analyses though. I
> >think that leaves plateosaurids as the only prosauropods (unless
> >Efraasia's position has stabilized), presumably with Saturnalia and
> >Thecodontosaurus still outside the Prosauropoda + Sauropoda clade.
>
> If Prosauropoda is limited to plateosaurids (either completely or in
> essence), I wonder if there's any point in keeping the term "Prosauropoda"
> at all. Plateosauria or just Plateosauridae would probably be a better
> term for this group, considering that the majority of taxa traditionally
> placed in the Prosauropoda are now regarded as either basal
> sauropodomorphs or basal sauropods. And the restricted composition of
> Prosauropoda sensu stricto makes the name ("before sauropods") even more
> inappropriate than it ever was. Just a thought...
In phylogenetic nomenclature this could be handled, for example, by defining
Plateosauridae as "everything closer to *Plateosaurus* than to
*Massospondylus*", and by registering it before Prosauropoda. So if
Prosauropoda became a junior heterodefinitional synonym of Plateosauridae,
Plateosauridae would have to be used as the valid name for the clade.
I fear we'll need to have a _large_ conference where people will work out a
finely crafted system of priority which would then need to be published in
the companion volume... The alternative is we'd have to live with a lot of
unpleasant names for unfamiliar contents, even with well thought-out
definitions. This issue is not trivial; in my limited experience it's one of
the most important reasons for opponents to the PhyloCode (...after
ignorance, that is...).