Message 2004-02-0017: Re: RE: a comment on ancestor

Sat, 07 Feb 2004 12:55:56 +0100

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Date: Sat, 07 Feb 2004 12:55:56 +0100
From: David Marjanovic <david.marjanovic@gmx.at>
To: PML <phylocode@ouvaxa.cats.ohiou.edu>
Subject: Re: RE: a comment on ancestor

> The prohibition may be implicit but to me it is there nonetheless.

It is there, yes. It is impossible to name, define and register paraphyletic
taxa under the PhyloCode.

But ironically, phylogenetic nomenclature is _better_ suited than Linnaean
nomenclature for defining paraphyletic taxa for the purpose of one paper (as
T. Mike Keesey has repeatedly pointed out). For example, "egg-laying
theropsids", "non-corvid passeriforms"... all these would require major
overturns of systematics under Linnaean taxonomy.

Clade names with self-destructive definitions, on the other hand, cannot
correspond to paraphyletic groups. If *Reptilia* were defined as "everything
closer to *Lacerta agilis*, *Crocodylus niloticus* and *Testudo graeca* than
(to) *Passer domesticus* and *Sorex araneus*, then it would simply not
exist -- there wouldn't be any reptile -- under all mainstream and
half-mainstream phylogenies. Under weird phylogenies (e. g if it were the
sistergroup of "Haematothermia"), it could exist, would have to be a clade,
and could have the same contents as the traditional doubly paraphyletic
Reptilia.

(In fact, I think *Reptilia* should be defined in such a way, to prevent the
huge change in content necessary to conform to its sometimes used
crown-group definition -- which includes birds but excludes theropsids, and
is almost identical to *Sauropsida*.)


  

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