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Date: Wed, 07 Feb 2001 16:46:03 -0500
From: Kevin de Queiroz <Dequeiroz.Kevin@NMNH.SI.EDU>
To: PhyloCode@ouvaxa.cats.ohiou.edu
Subject: Re: apomorphy-based names
In response to a previous posting from me, David Baum wrote: "It is true that we sometime conceptualize clades based on apomorphies. = For example, like most botanists I think of Angiospermae as being "defined" by the enclosure of ovules/seeds in carpels. (Perhaps this reflects some = kind of essentialistic core in us all that drives us to insert evidence [characters] as proxies for things [clades] whose existence we cannot directly observe.) However, I think that when we get to the point of naming a clade within the framework of the PhyloCode (or converting a preexisting name) we should be required to go beyond a "primitive," character-based understanding and say something about historical relationships. Thus, I think the name, "Angiospermae" should be attached to a specific genealogically specified clade: E.g.,"The most inclusive clade including Arabidopsis thaliana but not Gingko biloba, Pinus sylvestris, Welwitschia mirabilis......" or " the least inclusive clade including Amborella trichopoda, Nyphaea, etc......)." "Similarly, just because hair, mammary glands, a dentary-squamosal joint = or whatever (!) have been taken to "define" (I prefer "diagnose") a clade named Mammalia does not, in my mind, negate the responsibility to attach the name to one unambiguously indicated clade. And the least ambiguous = way to attach names to clade is using specifiers (and even then we are = assuming a strictly divergent tree [but that's another topic!])." First, apomorphy-based definitions also associate names with genealogically= specified clades. But the point I was trying to make is not that any = particular name, such as Angiospermae or Mammalia, out to be defined using = an apomorphy-based definition. Indeed, I would define both of these names = as the names of crown clades using node-based definitions. Instead, the = point I was trying to make was that someone might want to name the clade = stemming from the first species ancestral to Homo sapiens that evolved a = dentary-squamosal jaw articulation, and they ought to be able to do that. = =20 Kevin de Queiroz Division of Amphibians & Reptiles National Museum of Natural History Smithsonian Institution Washington, DC 20560-0162 Phone: (202) 357-2212 FAX: (202) 786-2979 e-mail: dequeirk@nmnh.si.edu