Message 2004-10-0037: Re: Panstems

Mon, 13 Sep 2004 11:54:35 -0400

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Date: Mon, 13 Sep 2004 11:54:35 -0400
From: [unknown]
Subject: Re: Panstems

Mickey Mortimerwrote-

Pan-stems already disrupt continuity for many names, as most total cl=
whose surrounding topologies are well known have been named already.

>This is true in the sense that some non-Pan names have already been =
defined as referring to total clades; however, the names have a much =
longer history than this, and they have also been associated with =
non-total clades (even after their first phylogenetic definitions), s=
o =3D
there is no disruption of continuity in the sense of loss of the name=
s.  =3D
Obviously, adopting a universal convention for a particular type of n=
ame =3D
will not be without some negative consequences.  These consequences h=
ave =3D
to be weighed against the benefit of making it a lot more easy to =
recognize the names, especially for people who work on other taxa (su=
ch as =3D
plants) and are familar with names such as Aves and Mammalia, but not=
 with =3D
Ornithosuchia (or 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 been one of the people w=
ho =3D
first defined several of them phylogenetically (de Queiroz and Gauthi=
er, =3D
1992).  Nevertheless, I think it would be a mistake to get too attach=
ed to =3D
these defintions, given that they have to official status under the =
PhyloCode (which will not be retroactive).  More importantly, as I th=
ink =3D
was stated in some earlier version of the PhyloCode preface or the =
webpage, the period of time between the first proposal of phylogeneti=
c =3D
definitions and the offical implementation of the PhyloCode is suppos=
ed to =3D
be treated as a period for experimentation.  If we decide that we cou=
ld do =3D
some things better, given a second chance, we should not let our earl=
ier =3D
decisions (mistakes?) constrain us.<

In addition, basically every 'family' or 'order'-level clade with liv=
representatives is understood to include some taxa basal to the crown
version of that clade.  So taxa directly basal to crown galliformes a=
placed in Galliformes too (e.g. Paraortygoides in Dyke and Van Tuinen=
2004).  Yet you would have us redefine Galliformes to be a crown clad=
e, =3D
make Paraortygoides a non-galliform pangalliform.  It's the same with
Diacodexis and Artiodactyla, Basilosaurus and Cetacea, etc..

>Continuity is never 100% in terms of hypothesized composition.  I wa=
s =3D
more concerned with the total loss of certain names--i.e., if ALL of =
the =3D
names are given standard affixes.<

Have existing total clade names been associated with more alternate
definitions than other kinds of clade names?  I don't think so.  The =
controversial clade names (Aves, Tetrapoda, Mammalia) are either crow=
n or
non-crown node-based clades.  If you really want to introduce a stand=
affix, crown clades have the least names associated with them.  But I=
with Jaime that recommending affixes for only one type of definition =
nonsensical.  Perhaps a better recommendation would be to keep existi=
names the same, but if you want to name a crown or total clade equiva=
lent =3D
an existing clade, use the pan- or acro- affixes.  This would cut dow=
n on
memorizing new clade names AND avoid disruptive renaming.

>I wasn't suggesting that names associated with total clades have bee=
n =3D
associated with more alternative definitions than those associated wi=
th =3D
other types of clades.  More importantly, if neonotologists (i.e., th=
e =3D
majortiy of biologists) acutally used the proposed crown clade names =
(e.g., Neotetrapoda, Neornithes) when talking about traits that can o=
nly =3D
be assessed in living organisms (and not in fossils), then I agree th=
at it =3D
would be logical to use the widely known names (e.g., Mammalia) for =
apomorphy-based clades and coin new names based on standard affixes f=
or =3D
the crowns (e.g., AcroMammalia).  Unfortunately, they don't.<

Kevin de Queiroz
Division of Amphibians & Reptiles
Smithsonian Institution
P.O. Box 37012
NHB, Room W203, MRC 162
Washington, D.C. 20013-7012
Voice:  202.633.0727
FAX:  202.357.3043


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