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Date: Fri, 15 Feb 2002 10:38:55 -0500
From: Kevin de Queiroz <Dequeiroz.Kevin@NMNH.SI.EDU>
To: tmk@dinosauricon.com, PhyloCode@ouvaxa.cats.ohiou.edu
Subject: Re: interesting style of definition
I just wanted to point out that this is not a new style of definition but = one (called a "stem-modified node-based definition") that has been = described and discussed in the literature. It is not particularly similar = to an apomorphy-based definition but instead uses components of both = standard node- and stem-based definitions (as implied by the name). See = Wyss and Meng 1996 Systematic Biology 45:559-568. Kevin de Queiroz >>> "T. Mike Keesey" <tmk@dinosauricon.com> 02/13/02 16:57 PM >>> I've just received _New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom_. The first chapter, "Feathered dinosaurs, flying dinosaurs, crown dinosaurs, and the name 'Aves'" by Gauthier and de Queiroz, should be of interest to anyone concerned with PhyloCode. It's written according to the draft PhyloCode rules and recommendations (i.e., italicized clade names, very specific and detailed definitions, etc.) There's a big emphasis, it seems, on using apomorphy-based clades and crown clades. Also, every stem-based clade mentioned has the prefix "Pan-" (_Panaves_, _Panpaleognathae_, _Panneognathae_, etc. -- all new clade names). One of the more interesting styles of definition used therein runs like so: "the crown clade stemming from the last common ancestor of A and all other extant organisms sharing a more recent ancestor with A than with B." (In essence, using the extant members of a stem-based clade as specifiers for a node-based clade.) This doesn't seem to me to be allowed under the draft PhyloCode, which states: "11.3. When a species is used as a specifier, the author and publication year of the species name must be cited" Only one of the specifiers (A) is being cited with author and publication year. (B is not a specifier of the clade in question.) The rest are identified by a formula, not by citation. Any thoughts on this style of definition? Should the final PhyloCode allow identification of specifiers through formulae, and not just direct citation? It seems useful to me (although potentially destabilizing if we find some extant member outside what had formerly been the crown group). ___________________________________________________________________________= __ T. MICHAEL KEESEY The Dinosauricon <http://dinosauricon.com> BloodySteak <http://www.bloodysteak.com> personal <keesey@bigfoot.com> --> <tmk@dinosauricon.com> Dinosauricon-related <dinosaur@dinosauricon.com> AOL Instant Messenger <Ric Blayze> ICQ <77314901> Yahoo! Messenger <Mighty Odinn>