Message 2005-08-0005: Re: Aliwalia [from Adam Yates]

Sat, 13 Aug 2005 00:52:08 +0200

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Date: Sat, 13 Aug 2005 00:52:08 +0200
From: David Marjanovic <>
To: DML <>
Cc: PML <>
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- According to a new, unpublished analysis, the traditional Prosauropoda is 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...). 


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