Message 2001-02-0017: Re: apomorphy-based names

Tue, 06 Feb 2001 11:31:01 -0600

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Date: Tue, 06 Feb 2001 11:31:01 -0600
From: "David M. Hillis" <>
Subject: Re: apomorphy-based names

At 11:38 AM -0500 2/6/01, Kevin de Queiroz wrote:
>my point was not the VP workers are more inclined to use explicit 
>apomorphy-based definitions but that it is often clear that they 
>really have an apomorphy-based concept of certain clades even when 
>they define the names of those clades using other types of 
>definitions!  And that's true for some of the clades of non-crown 
>"birds," where node-based definitions are used when the authors seem 
>to have an apomorphy-based concept of the clade they are intending 
>to name.  Jacques may be able to provide more details on this.

I don't have any problem with this...I suppose we all often think 
about clades from the standpoint of what they look like. But I think 
we can be more explicit and phylogenetically clear in our definitions 
by naming clades using node-based and stem-based definitions, even if 
we originally conceptualize those clades based on apomorphies. I 
agree with David Baum that a nomenclature that expresses an explicit 
tree is preferable to one that relies on the supposed fixation of a 
particular trait that may or may not be unambiguously defined or 
interpreted. Naming node-based and stem-based taxa seems to be the 
trend, even in vertebrate paleontology, and even, as Kevin points 
out, when the clades are originally conceptualized on the basis of 
particular apomorphies. I think that is a good thing.

David M. Hillis
Director, School of Biological Sciences
Director's office: 512-232-3690 (FAX: 512-232-3699)
Alfred W. Roark Centennial Professor
Section of Integrative Biology
University of Texas
Austin, TX 78712
Research Office: 512-471-5792
Lab: 512-471-5661
FAX: 512-471-3878


Feedback to <> is welcome!