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Date: Fri, 24 Aug 2001 11:20:42 -0400
From: Kevin de Queiroz <Dequeiroz.Kevin@NMNH.SI.EDU>
To: david.marjanovic@gmx.at, phylocode@ouvaxa.cats.ohiou.edu, dinosaur@usc.edu
Subject: Re: Apomorphy-based definitions
I think you are misconstruing function of the specifier Passer in the = definition, which is not to define the what is meant by "feathers" but to = protect the definition against homoplasy. Thus, saying that the feathers = are synapomorphic with those in Passer does not mean that they must be = more similar to those in Passer than to those in ratites. It only means = that whatever features we consider necessary to call something a feather = (presumably shared by Passer and ratities) must be shared with Passer as = the result of inheritance from a common ancestor for the organism to be = considered to fit the definition. The only way that ratities would be = excluded is if they evolved their feathers homoplastically with those in = Passer. Note that the PhyloCode (Rec. 9F) recommends that if an apomorphy-= based definition is used, the apomorphy needs to be described in sufficient= detail that users of the definition can understand the author's intent. = Therefore, you wouldn't just say "feathers homologous with those in = Passer"; you would also have to specify what you meant by "feathers." >>> David Marjanovic <david.marjanovic@gmx.at> - 8/23/01 5:11 PM >>> > This definition would be a very bad idea. For one thing, the feathers = of *Passer* are suddenly > the defining feature for feathers as a phylogenetic tool; ratite = feathers are different, foir the > bulk of their morphology, and it is conceivable that Ratitae would be excluded from this > definition. Completely true; I have used this example because I have read it somewhere (probably Sereno's rationale in Neues Jahrbuch) and for a moment thought = it was in the PhyloCode (wrong).