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Re: Panstems

On 14/9/04 8:19 am, "T. Michael Keesey" <mightyodinn@yahoo.com> wrote:
> http://dino.lm.com/keesey/documents/PhylogeneticNotation.doc

    One point which I've noticed in the exemplar definitions, which isn't a
problem with Mike's proposed notation, but a problem arising from one of the
definitions -'Panaves'. My question is - how are we to properly define crown
clades? Simply defining them as node clades doesn't seem sufficient, as we
should allow for the possibility that some of the living members may
eventually be moved phylogenetically outside the proposed node.
    Mike defines Panaves as the panstem clade of the node Struthio + Tetrao
+ Vultur. Under the current popular phylogenies, this wouldn't really be a
problem - whichever the most basal branch of Aves is, most researchers would
currently hold it to include one of these three. But among other taxa that
have been suggested in the past to be the most divergent living birds are
Mesitornithidae, _Opisthocomus_ and _Todus_ (!). Conceivably, we could get a
situation where these are not Aves. By some older molecular phylogenies,
Passeriformes would not even be Aves by the definition given. What to do?


        Christopher Taylor