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Re: Pteros might be dinos?!? Oh no ...



On Tue, Nov 10, 2009 at 4:47 PM, Augusto Haro <augustoharo@gmail.com> wrote:
> The Phylocode-experts here may tell me if for phylogenetic definitions
> there is a rule of priority.

There is no active code that covers phylogenetic definitions, so you
can do whatever you want to do. The PhyloCode should be implemented
within the next few years, so then we'll have a standard (although it
remains to be seen how widely followed it will be). Once Dinosauria is
defined under PhyloCode rules, then we can talk about priority.

> In the recent paper of Langer et al.
> (2009) it is said that the first to phylogenetically define Dinosauria
> is Novas (1992), and in this work he specifically considered this
> taxon as a specifier of the Dinosauria, and according to him, also
> Gauthier (1986). However, today we accept a definition without
> Herrerasaurus as a specifier, by Padian and May (1993). Why is this
> so?

Because Herrerasaurus is not an "essential" member of Dinosauria.
Padian and May's definition fails this test, too, since one of the
specifiers is "birds" (which are, if anything, even less essential).
Olshevsky's (2000) definition uses Megalosaurus and Iguanodon, which
were two of the original members of Dinosauria and have been included
in every usage since. The draft PhyloCode also endorses using the
original members (all three of which have always been considered
dinosaurs, under all usages of the term) as specifiers in one of its
recommendations.

Of course, this discussion is pretty much academic, since all of these
definitions are currently thought to indicate the same clade.
-- 
T. Michael Keesey
Technical Consultant and Developer, Internet Technologies
Glendale, California
http://tmkeesey.net/