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Date: Tue, 19 Oct 2004 08:35:58 -0400
From: [unknown]
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: applying widely known names to crown clades
Jason Anderson wrote: > >Thus, as I asked in my first email and ask again now, >why are we persisting on keeping Tetrapoda attached to the crown, an= d use >Holotetrapoda for the apomorphy-based definition, when using Tetrapo= da and >Neotetrapoda (or whatever) is logically just as consistent, but >additionally, will maintain consistency with the literature, and mor= eover >might help to bring more workers onside? As I wrote to Jason in an email message last spring (and I would like= =20 to share with the rest of you now), I am less interested in the=20 applications of particular names than I am in developing a system= =20 whose consistency will (1) help users to understand and remember the= =20 phylogenetic meanings of names and (2) convey a limited amount of= =20 phylogenetic information directly in the name (e.g., that Pan-X is= =20 the total clade corresponding to crown clade X). There are other conventions that would also offer such advantages.= =20 For example, widely used names that refer to a character (e.g.,=20 Tetrapoda) could be applied consistently to apomorphy-based clades,= =20 with Neo- and Pan- referring to the corresponding crown and total= =20 groups, respectively. However, from a practical standpoint, this= =20 convention would not work as well. If the apomorphy referred to in a= =20 name doesn't fossilize (e.g., Embryophyta), there would be many=20 extinct organisms whose membership in the clade could not be=20 determined. Also, if a widely used name doesn't refer to a character= =20 (e.g., Plantae), which synapomorphy-based clade should the name apply= =20 to if the crown clade has more than one synapomorphy? Another option would be to apply widely known names consistently to= =20 total groups, with Neo- referring to the corresponding crown, but= =20 this would present a different problem. Some character-based names= =20 would necessarily apply to clades whose basal members lack the=20 character. For example, the total clade that would be named=20 Spermatophyta under this convention would include extinct plants that= =20 predated the evolution of seeds. I agree with Jason that an apomorphy-based application may be most= =20 consistent with traditional usage of certain well known names, but I= =20 place higher priority on the advantages of consistency in application= =20 of widely used names. Because applying such names consistently to= =20 crown clades does not have the practical problems that applying them= =20 consistently to apomorphy-based or total clades would have, I favor= =20 the former. Phil --=20 Philip D. Cantino Professor and Associate Chair Department of Environmental and Plant Biology Ohio University Athens, OH 45701-2979 U.S.A. Phone: (740) 593-1128; 593-1126 Fax: (740) 593-1130 e-mail: cantino@ohio.edu