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Re: PRIORITY RULES



>Hey folks.
>
>Wagner and I have been having an all-out email war over use of the terms Aves
>and Avialae. He says Avialae should be used because of priority, but I
>said that
>priority rules don't go for higher taxa, PLUS 'Aves' is just a tad older than
>'Avialae' (like, more than 230 years older..). But _he_ says that, under
>the new
>clad-rules, priority goes for whichever term was first published in a
>phylogenetic context (i.e. defined in a cladistic framework) _and_ these
>priority rules apply to all taxon names.

There does not need to be conflict between Aves and Avialae IMHO; Avialae
(sensu Gauthier) is a stem-based taxon, while Aves (as most workers would
use it) is node-based. Chiappe and others have recently (e.g the Mononykus
paper in the Gondwanan dinos volume, and other recent papers by Chiappe)
explicitly defined Aves as the most recent common ancestor of the
Neornithes (as used by many ornithologists for the crown group birds) and
Archaeopteryx, and all descendants of that MRCA.

This does conflict with Gauthier's use of Avialae as the sister taxon for
Deinonychosauria, as Novas and others have stuck with. Following Chiappe's
definition, "birds" refers to Aves proper, and "modern birds" refers to
Neornithes. This uses a genealogically-based rather than apomorphy (e.g.
wings and feathers) -based definition, which is more stable and more
faithful to the original spirit of Hennig than apomorphy-based definitions,
as I think most people now agree.

The controversy over the use of Aves is quite similar to that surrounding
Mammalia (see recent papers by Rowe, Wible, Hopson, etc., etc.): crown taxa
for commonly used names (as Gauthier, Rowe, DeQueiroz, etc. advocate: MRCA
of Theria and Monotremata AADOTMRCA) or commonly used names for major,
traditional groupings (including fossils, like tritheledontids) and/or
groups sharing a particular "important" feature (e.g. dentary-squamosal jaw
joint)? A sticky situation, but it looks like there's hope for a consensus.

Well, that's my opinion anyway. SVP this year and some upcoming papers
(e.g. Currie and Padian's Encyclopedia of Dinosaurs, and others) will
clarify the issue further.

                       --John R. Hutchinson