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Date: Thu, 26 Apr 2001 14:00:23 -0400 (EDT)
From: "T. Mike Keesey" <tmk@dinosauricon.com>
To: -PhyloCode Mailing List- <PhyloCode@ouvaxa.cats.ohiou.edu>
Subject: Re: Fwd: Vermes
Just going to include Recommendation 10A:
"Clade names should be selected in such a way as to minimize disruption of
current usage. When establishing the name of a clade, a preexisting name
that has been applied to this clade should generally be selected if such a
name exists. If more than one preexisting name has been applied to the
clade, the name that is most widely and consistently used for it should
generally be chosen. Similarly, if a preexisting name is phylogenetically
ambiguous because it has been applied to more than one clade, it should
generally be established for the clade to which it has been most widely
and consistently applied. If there is no preexisting name for the clade,
or if all preexisting names are so phylogenetically ambiguous that their
use may cause confusion, a preexisting name that has been applied to a
paraphyletic group stemming from the same ancestor may be used, or a new
name may be established."
For those unfamiliar with the groups in question, Synapsida is a singly
paraphyletic Subclassis of Classis Reptilia under traditional taxonomy,
and it includes the so-called "mammal-like reptiles" (better termed
"proto-mammals" -- _Dimetrodon_, _Cynognathus_, etc.). Under cladistic
usage, it has been divorced from _Reptilia_ and now, in addition to the
traditional members, includes _Mammalia_. The definition could be stated
as Clade(_Cynognathus crateronotus_ <-- _Passer domesticus_) (the latter
being an avian -- I was going to use our own species as the internal
specifier, but then I remembered Recommendation 11A) or an equivalent
formula. However, the clade had already been named Theropsida under the
traditional system, although its usage was not prevalent.
(Correct me if anything's wrong here.)
On Tue, 24 Apr 2001, Kevin de Queiroz wrote:
> Actually, the situation is somewhat complicated, and Recommendation
> 10A does not actually say that a name that was previously used to
> refer to a paraphyletic group should not be used in preference to one
> that has been explicitly used for the clade in question. The reason
> is that the advantages of using a name that has been explicitly
> applied to a clade can be offset by its lack of familiarity and use.
> One of the primary functions of taxon names is to provide access to
> the literature, and therefore it may sometimes be preferable to use a
> name that was formerly applied to a paraphyletic group if that name is
> more widely known and used. Thus, the person who first establishes
> the name of a particular clade (the "first revisor") has the
> responsibility of making a thoughtful decision. The case or
> "Synapsida" vs. "Theropsida" is a good example of this tradeoff.
It could also be argued that, if you really want to cause minimal
disruption, a previously named clade, however obscure, should be chosen
over greatly expanding a paraphyletic group. The first two sentences of
this recommendation would seem to advocate, although not require, usage of
_Theropsida_ over _Synapsida_, and the final sentence would support usage
of _Synapsida_ only if _Theropsida_ had not already been named.
Personally, I don't mind using _Synapsida_ (and _Therapsida_) as clades --
I've done so for years. I'm just thinking of "selling" the system to a
wider audience, some of whom may find these conversions (and those of
_Reptilia_, _Osteichthyes_, etc.) hard to swallow, especially when other
names for the clades are already in existence (however obscure).
_____________________________________________________________________________
T. MICHAEL KEESEY
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