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Date: Mon, 05 Feb 2001 14:45:14 -0600 (CST)
From: "Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>
To: PhyloCode@ouvaxa.cats.ohiou.edu
Subject: Addendum 3: Specifiers for non-apomorphy-based apomorphy-derived clade names
All,
In reviewing the literature for an upcoming paper, the issue of the
names of apomorphy-based clades, and the definitions of clades named after
apomorphies came up. Not that I believe there is any need for strict rules
on this subject, but I felt that the following three recommendations might
be appropriate. Note that I have sent them separately, although they should
probably be considered as part of the same discussion.
Jonathan R. Wagner
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Draft item (Recommendation 11.8E?) for PhyloCode, Article 11
Recommendation 11.8E: For logical consistency, in a stem- or node-based
definition of a clade named for an apomorphy, internal specifiers should be
chosen that unambiguously exhibit the nominal apomorphy. External specifiers
should be chosen that unambiguously lack the apomorphy.
Example: Sereno (1999) defined _Ankylopollexia_ Sereno 1986 using a
node-based definition specified internally by _Camptosaurus dispar_ (Marsh
1879) and Parasaurolophus walkeri Parks 1922. However, the latter taxon does
not even possess a pollex, indeed, no hadrosaurid does. Definition of this
clade name as "the least inclusive clade containing _Camptosaurus dispar_
(Marsh 1879) and _Iguanodon bernissartensis_ Boulenger_et_van Beneden 1881
would, under most phylogenetic hypotheses, encompass the same group.
However, should these taxa be found to form an exclusive group united by
their common thumb, other taxa without the ankylopollexian condition would
not be retained in the group.
--------------------------------------------------------------------------------
Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
"Why do I sense we've picked up another pathetic lifeform?" - Obi-Wan Kenobi