Message 2004-10-0188: Re: RE: crown clade convention

Tue, 19 Oct 2004 18:13:17 -0400

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Date: Tue, 19 Oct 2004 18:13:17 -0400
From: [unknown]
Subject: Re: RE: crown clade convention

A few responses to Jason's comments.  My responses are in > <.

The fact that Neotetrapoda hasn't been used isn't in my mind really s=
evidence since Gauthier, Kluge and Rowe formally ignored it in Phylog=

Nomenclature a mere 8 years after Gaffney suggested it, opting for th=
e =3D
convention because of problems seen with apomorphy-based definitions =
argued by you and Jacques in 1990) that have subsequently been either
corrected or shown false. Neotetrapoda has never received the weight =
authority that either the 1988 paper or the publication of the compan=
volume would lend (which I see as a great opportunity to educate
nonsystematists as to the importance in precision of name use). Still=
, I =3D
your point.

>The same is true for Neornithes, coined for the bird crown clade.  =
Neontologists hardly ever use this name even when it is the appropria=
te =3D
one to use (e.g. "avain molecular systematics").  I'm not sure how on=
e is =3D
to judge "weight of authority", but I would think that in 1988 Gaffne=
y, a =3D
leading phylogeneticist, was viewed as carrying more authority than e=
ither =3D
Gauthier or Rowe, who were relative newcomers at the time.  (Aside:  =
I =3D
don't remember arguing that apomorphy-based definitions were problema=
tic =3D
in the 1990 paper.  I've always been a supporter of all 3 of the orig=
 proposed types of phylogenetic definitions.)<

What is "best for biology" is for everybody to mean the same thing wh=
en we
use a name, thus either the crown or apomorphy definition is suboptim=
al. =3D
the former case, there will be confusion engendered when "tetrapods" =
are =3D
longer "Tetrapods", which will not only be among paleontologists but =
the educated general public who read Jenny Clack's or Carl Zimmer's r=
books, and among neontologists who still consider tetrapods to be lim=
vertebrates even if some of their papers are less than precise. In th=
latter case, the confusion will continue to be as Michel and Kevin ha=
characterized it, with inaccurate statements entering the literature =
I still think is a by product of an overly pedantic, literal reading =
of =3D
literature). So the real question in my mind is how one determines wh=
confusion is potentially greater, and I'm not so sure how that is don=
objectively. At this stage preference for either option seems to be b=
ased =3D

>I don't see a big problem with calling them tetrapodomorphs, rather =
than =3D
tetrapods.  In addition, I have to reiterate my earlier point that th=
e =3D
problem is not only the imprecise use of the well known names (which =
Jason =3D
attributes to an overly literal reading of the statements in question=
, "tetrapods express gene y") but the fact that less well know names =
coined specifically for the crowns (e.g., Neotetrapoda) are consisten=
tly =3D
avoided by neontologists in precisely those situations when it would =
be =3D
appropriate to use them.<

Regarding your number 2, respectfully, there has been an awful lot of=
spilled over the clade of limbed vertebrates over the past ten years,
including in the neontological literature. Obviously biologists have =
a lot
to say about this group (which they call "Tetrapoda").

>I didn't mean to imply that people didn't have much to say about the=
clade of limbed vertebrates--they clearly do.  That's why we most =
definitely need a name for that clade.  The point I was trying to mak=
e is =3D
that many more statements can be made about crown clades in terms of =
characters that are not commonly preserved in fossils (e.g., about ge=
nes, =3D
gene expression, physiology, behavior, etc.) and therefore it makes s=
ense =3D
to use the best known names for those clades.  In fact, this is basic=
ally =3D
the reason that the widely known names are commonly used imprecisely.=
There are many statements that neontologists want to make (i.e., abou=
t =3D
rarely fossilized characters) that are justifiable only if interprete=
d as =3D
statements about the crown; however, neontologists also want to use t=
he =3D
widely known names.  Therefore, they use the widelly known names AS I=
F =3D
those names refer to the crowns despite the fact that those names are=
supposed to refer to more inclusive clades and other less well known =
names =3D
are supposed to refer to the crowns.  Because of the simple differenc=
e in =3D
numbers of neontologists versus paleontologists and the greater willi=
 that the latter group has shown to use the widely known names for th=
e =3D
crowns than the fomer group has shown to use the less widely known na=
mes, =3D
it seems that the most efficient way to achieve consistency is to ado=
pt =3D
the crown clade convention.  Of course, this means that the paleontol=
 have to do the neontologists a favor.  Basically, what we're asking =
is =3D
for Jason and other paleontologists to consider changing their otherw=
ise =3D
logical and traditional use of names to achieve greater overall consi=
 of use.  I realize that this is a big favor to ask, but I have a hig=
h =3D
opinion of paleontologists and think that there is a chance that they=
 may =3D
ultimately be willing to do it.<

19 Oct 2004


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