Message 2004-10-0040: Re: Panstems

Mon, 13 Sep 2004 18:49:05 +0200

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Date: Mon, 13 Sep 2004 18:49:05 +0200
From: [unknown]
Subject: Re: Panstems

Dear phylocoders,

Kevin wrote:

>  >This is true in the sense that some non-Pan=3D20
>names have already been defined as referring to=3D20
>total clades; however, the names have a much=3D20
>longer history than this, and they have also=3D20
>been associated with non-total clades (even=3D20
>after their first phylogenetic definitions), so=3D20
>there is no disruption of continuity in the=3D20
>sense of loss of the names.

=09I don't entirely agree here.  There is=3D20
disruption of usage if the most common meaning of=3D20
the name was the stem-based clade or a comparable=3D20
taxon under rank-based codes, or if that name=3D20
used most often for that stem-based clade would=3D20
be lost in favour of a Pan-based name.  This is=3D20
certainly the case of Synapsida (=3D3DPanMammalia),=3D20
to cite my favourite example.

>Obviously, adopting a universal convention for a=3D20
>particular type of name will not be without some=3D20
>negative consequences.  These consequences have=3D20
>to be weighed against the benefit of making it a=3D20
>lot more easy to recognize the names, especially=3D20
>for people who work on other taxa (such as=3D20
>plants) and are familar with names such as Aves=3D20
>and Mammalia, but not with Ornithosuchia (or=3D20
>Avemetatarsalia) and Synapsida.<
>Here are some total clade names that come to mind-
>Amphibia =3D3D Panlissamphibia.
>Salientia =3D3D Pananura.
>Urodela =3D3D Pancaudata.
>Reptiliomorpha =3D3D Panamniota.
>Synapsida =3D3D Panmammalia.
>Metatheria =3D3D Panmarsupalia.
>Eutheria =3D3D Panplacentalia.
>Sauropsida =3D3D Panreptilia.
>Anapsida =3D3D Pantestudines.
>Romeriida =3D3D Pansauria.
>Lepidosauromorpha =3D3D Panlepidosauria.
>Archosauromorpha =3D3D Panarchosauria.
>Avemetatarsalia =3D3D Panaves.
>Many of these names are very commonly used.  Changing them all would=
>quite disruptive.
>  >Obviously, I'm aware of these names, having=3D20
>been one of the people who first defined several=3D20
>of them phylogenetically (de Queiroz and=3D20
>Gauthier, 1992).  Nevertheless, I think it would=3D20
>be a mistake to get too attached to these=3D20
>defintions, given that they have to official=3D20
>status under the PhyloCode (which will not be=3D20

=09Here, I believe that Kevin is=3D20
disregarding a point that some of us tried to=3D20
make at the meeting and that is related to=3D20
Mickey's comment.  Namely, systematists want to=3D20
keep these names for stem-based clades because=3D20
this is more or less the way that they have been=3D20
conceptualized (or at least delimited) by=3D20
generations of systematists.  For about a=3D20
century, Synapsida has referred to the stem of=3D20
Mammalia, and in the last 20 years or so, it has=3D20
come to include mammals too, a necessary change=3D20
to make it monophyletic.  It is because of the=3D20
long history of this name that many of us want to=3D20
keep it, not because Kevin and Jacques defined it=3D20
twelve years ago (although I agreed with the=3D20
definition that they provided at the time and=3D20
have used the name in that sense consistently).=3D20
Parenthetically, other taxa have a lateral=3D20
fenestra but were not included in Synapsida (at=3D20
least in the last 50 years), such as some=3D20
parareptiles.  Indeed, the fenestra is so common=3D20
in early amniotes that Reisz raised the=3D20
possibility that it might be an apomorphy of=3D20
amniotes lost in the "anapsids", so redefining=3D20
Synapsida on the basis  of the fenestra would be=3D20
a really bad idea.  Similarly, when I proposed=3D20
(with Reisz) phylogenetic definitions of=3D20
Parareptilia (=3D3DPanTestudines) and Eureptilia=3D20
(=3D3DPanSauria), I used Everett Olson's terminology=3D20
(proposed in the 1940s), that had been used by=3D20
several other paleontologists (even in Russia).=3D20
If I want to keep these names, it is not only=3D20
(not even mostly) because we have used these=3D20
names in the last 10 years in PN but rather,=3D20
because these definitions reflect the use of=3D20
these names in the literature (rank-based and PN).

=09One of the most common critique of the=3D20
PhyloCode is that it will generate many new names=3D20
and disrupt continuity with the literature; that=3D20
is certainly not true of the PhyloCode as it now=3D20
stands, but it COULD be true if the use of the=3D20
Pan- prefix for total clades is made mandatory=3D20
for most such clades.  Let's not give critiques=3D20
of the PhyloCode such an obvious problem to point=3D20


Michel Laurin
=3D46RE 2696, CNRS
Universit=3DE9 Paris 7 - Denis Diderot
2, place Jussieu
case 7077
75005 Paris

tel. (33 1) 44 27 36 92

Secretary of the International Society for Phylogenetic Nomenclature


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