Message 2004-10-0189: RE: RE: crown clade convention

Tue, 19 Oct 2004 17:07:59 -0700

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Date: Tue, 19 Oct 2004 17:07:59 -0700
From: [unknown]
To: 'Kevin de Queiroz' <Dequeiroz.Kevin@NMNH.SI.EDU>, "''" <
Subject: RE: RE: crown clade convention

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

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

True, Gaffney probably was seen as more of an authority at the time. =
I am
extrapolating back our current concern for priority of definitions to=
 a time
when such an idea didn't exist beyond the statement "first associatio=
n of a
name with a clade" (as I recall). Given that principle at the time, I=
find it odd that Gauthier et al. would ignore Gaffney's association o=
Neotetrapoda with the crown. Had they followed his first use of this =
associated with that clade, we wouldn't be having this discussion, be=
Ichthyostega would still be in Tetrapoda (which, following rank-based
classification, it still is--thus my fear of a split in taxonomy).

In the context of the opinions of the late 80s, I am pretty sure that=
biologists didn't adopt the name Neotetrapoda because they didn't see=
need, probably due to a lack of an appropriate slot within the rank
hierarchy. Romer's classic classification of 1966 in fact didn't use =
(or Tetrapoda), although in that text he certainly recognized its rea=
and explicitly mentioned it as an alternative way to classify tetrapo=
ds in
the text. Ditto Carroll's 1988 classification--Amniota (and Tetrapoda=
) is
not used, Superclass or otherwise, despite titling one of the chapter=
s in
that text "primitive amniotes and turtles". In the minds of these
taxonomists, the best classifications are simple, not laden with mult=
redundancies. Amniota and Tetrapoda in Carroll's view are ways of gro=
classes (explicitly recognizing their singular evolutionary origin, C=
1988, p.16). And in my opinion this is the root of the imprecision in=
of most nonsystematists today. As we are more successful and the Phyl=
is considered more thoroughly, folks will become better educated abou=
t the
importance of tree thinking, and overall consistency will be achieved=
. That
is why I speak about abrogating our responsibility; most biologists a=
still deep in Evolutionary Taxonomy. By accommodating the errors crea=
ted by
older thinking, we will create an entirely new set of problems.

(Sorry--my copy of the 1990 paper is buried somewhere and I am going =
> >I don't see a big problem with calling them tetrapodomorphs, rathe=
r than
> tetrapods.  In addition, I have to reiterate my earlier point that =
> problem is not only the imprecise use of the well known names (whic=
h Jason
> attributes to an overly literal reading of the statements in questi=
> e.g., "tetrapods express gene y") but the fact that less well know =
> coined specifically for the crowns (e.g., Neotetrapoda) are consist=
> avoided by neontologists in precisely those situations when it woul=
d be
> appropriate to use them.<
As Michel pointed out, Tetrapodomorpha is imprecise, including porole=
osteolepiform, and panterichthyd  fishes. I would not expect it to pr=
ove an
adequate alternative.

What I mean by overly literal is that there is a secondary, unspoken,
condition that you assume in order to conclude that these names are u=
imprecisely: let me state it. You must assume "tetrapod" is equivalen=
t to
"member of Tetrapoda", as Michel did in the Point-Counterpoint, which=
why I rejected this whole line of reasoning out of hand at the time.
Furthermore, my opinion survey shows this is not a universal practice=
. Phil,
one of the foremost thinkers about taxonomy and nomenclature, only TH=
MORNING decided that "tetrapod" probably isn't a real vernacular word=
the opinion of the greater community is still out. How can we hold
nonsystematists to distinctions they do not know exist when discussin=
g the
results of their papers?

There is another possible factor at play: interpreting statements mad=
e in
evolutionary taxonomy through the filter of P.N. I made the point in =
debate paper that stating "extant tetrapods express gene Y" is redund=
because it cannot be anything else, and some editors might actively e=
"extant" from that statement. Some authors do state "extant" explicit=
(most don't), but I certainly would never be fooled into thinking tha=
t that
statement can be generalized to the entire clade. Has communication b=
impeded in this case? Do you really read papers in this literal manne=
r? If
they wished to extrapolate their results to the entire clade they wou=
explicitly state whatever finding is a characteristic of Tetrapoda, a=
that only a vanishingly small group use in their papers (from my anal=
ysis of
a portion of Michel's literature survey). In fact, most of the exampl=
es used
in that literature survey, as I was able to find out by reading the
articles, used Tetrapoda, when explicitly stated, in a traditional, I=

Yes there is imprecision. I believe it is due to the dominance of Evo=
and it is corrected by pushing the advantages of tree thinking. What =
authors do is say "tetrapods express Y and fish express Z", informal =
highly inaccurate (when "fish" really means Danio and "tetrapods" mea=
Xenopus and Mus) yes, but discussions about character state distribut=
across clades they are not, so we should not treat them as such. We c=
even be sure these statements apply across the crown. We should, howe=
get authors and editors thinking about these issues.

> Regarding your number 2, respectfully, there has been an awful lot =
of ink
> spilled over the clade of limbed vertebrates over the past ten year=
> including in the neontological literature. Obviously biologists hav=
e 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 t=
> 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 m=
ake is
> that many more statements can be made about crown clades in terms o=
> characters that are not commonly preserved in fossils (e.g., about =
> gene expression, physiology, behavior, etc.) and therefore it makes=
> to use the best known names for those clades.  In fact, this is bas=
> the reason that the widely known names are commonly used imprecisel=

I would agree this is a good reason that crown clades deserve names, =
but I
agree with other workers that it does not necessarily follow that tha=
t name
should be the well-known one, especially when this requires decouplin=
g the
name from its widely understood meaning. And as I suggested above, an=
reason for imprecision in name use could come from the still dominant
paradigm of Evolutionary Taxonomy, which doesn't value tree thinking =
highly as PN (which is primarily tree based).

> There are many statements that neontologists want to make (i.e., ab=
> rarely fossilized characters) that are justifiable only if interpre=
ted as
> statements about the crown; however, neontologists also want to use=
> widely known names.  Therefore, they use the widelly known names AS=
> those names refer to the crowns despite the fact that those names a=
> supposed to refer to more inclusive clades and other less well know=
n names
> are supposed to refer to the crowns.  Because of the simple differe=
nce in
> numbers of neontologists versus paleontologists and the greater
> willingness that the latter group has shown to use the widely known=
> for the crowns than the fomer group has shown to use the less widel=
y known
> names, it seems that the most efficient way to achieve consistency =
is to
> adopt the crown clade convention.  Of course, this means that the
> paleontologists have to do the neontologists a favor.  Basically, w=
> we're asking is for Jason and other paleontologists to consider cha=
> their otherwise logical and traditional use of names to achieve gre=
> overall consistency of use.  I realize that this is a big favor to =
> but I have a high opinion of paleontologists and think that there i=
s a
> chance that they may ultimately be willing to do it.<

Believe me, Jason is considering it. Its why we're having this discus=
sion. I
need to continue thinking about how overall consistency of use will b=
e best
achieved. I only hope my position is considered as carefully as I am
considering the alternative, because I feel just a bit like Kate from
"Taming of the Shrew" at the moment.

Cheers, Jason


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