Message 2004-10-0191: Re: RE: RE: crown clade convention

Wed, 20 Oct 2004 14:34:45 -0400

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Date: Wed, 20 Oct 2004 14:34:45 -0400
From: [unknown]
Subject: Re: RE: RE: crown clade convention

>A few more comments on this issue (probably my last, at least for a =
month =3D
or so).<

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 =3D
when such an idea didn't exist beyond the statement "first associatio=
n of =3D
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).

>The reason that Gauthier et al. did not use Gaffney's Neotetrapoda w=
as =3D
that they (explicitly) adopted the crown convention for widely known =
names!  See page 106.<

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, =
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=
. =3D
is why I speak about abrogating our responsibility; most biologists a=
still deep in Evolutionary Taxonomy. By accommodating the errors crea=
ted =3D
older thinking, we will create an entirely new set of problems.

>The lack of use of Tetrapoda in taxonomies that emphasize the tradit=
ional =3D
classes (Amphibia, Reptilia, Aves, Mammalia) doesn't explain its impr=
ecise =3D
use when used.  The errors in question are not caused by older thinki=
ng as =3D
much as by the fact that neontologists want to use the well known nam=

(Sorry--my copy of the 1990 paper is buried somewhere and I am going =

>(Perhaps you're confusing our paper with one by Harold Bryant.)<
As Michel pointed out, Tetrapodomorpha is imprecise, including porole=
osteolepiform, and panterichthyd  fishes. I would not expect it to pr=
ove =3D
adequate alternative.

>Then we can use Tetrapodiformes or Tetrapodalia or Holotetrapoda or =
some =3D
other name that includes the same Greek stems.<

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=
. =3D
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?

>I think the point that Phil was trying to make was that we needn't =
concern ourselves with vernacular names, since the PhyloCode only =
regulates scientific names.  In any case, it doesn't seem unreasonabl=
e to =3D
assume that people will equate "tetrapod" with "member of Tetrapoda" =
given =3D
that the former is basically a vernacularized version of the latter (=
at =3D
least in English).  In fact, I've proposed exactly this equivalence f=
or =3D
"mammals" and "member of Mammalia" in one of my philosophical papers =
(Biology and Philosophy 10:224).<

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 =3D
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 =3D
a portion of Michel's literature survey). In fact, most of the exampl=
es =3D
in that literature survey, as I was able to find out by reading the
articles, used Tetrapoda, when explicitly stated, in a traditional, I=

>Although I think I understand what you are saying here, it seems to =
me =3D
that "extant tetrapods express gene y" is only truly redundant if =
tetrapods/Tetrapoda refers to the crown.  In any case, the question i=
sn't =3D
whether I read papers in a literal manner (though it would make life =
easier).  The question is wouldn't it be better if the names that peo=
ple =3D
used in these situations were the appropriate ones so that we wouldn'=
t =3D
have to worry about whether it's appropriate to read them in a litera=
l =3D

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.

>We all recognize the problems of limited sampling, but more taxa are=
eventually sampled (Gallus, Sus, Ambystoma, etc.) and at some point p=
eople =3D
start making generalizations about the whole clade.<

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 =3D
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).

>The two possibilities we have been considering are: 1) to associate =
the =3D
well known name with the crown and use a different one for the more =
inclusive group, or 2) to use the well known name for the more inclus=
ive =3D
group and a different one for the crown.  Both approaches have advant=
ages =3D
and disadvantages.  The one thing I definitely would not want to do i=
s =3D
adopt the crown convention for most well known names but make just a =
few =3D
exceptions, such as for Tetrapoda.< =3D20

Believe me, Jason is considering it. Its why we're having this discus=
sion. =3D
need to continue thinking about how overall consistency of use will b=
e =3D
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.

>Great.  I can guarantee you that your position is being considered =
carefully, at least by me.  I don't really have time to be engaging i=
n =3D
this discussion right now, but I decided that it was important enough=
 to =3D
do it.  Also, I don' t really have an investment in the crown convent=
ion, =3D
but every time I consider an alternative I keep coming back to the cr=
own =3D
convention because it seems to result in the cleanest overall approac=
h.  =3D
Another thing that hasn't played much of a role in the present discus=
sion =3D
is the name of the total clade.  If we consider that also, the set =
PanTetrapoda (total), Tetrapodiformes (apo), and Tetrapoda (crown) se=
ems =3D
cleaner than the set PanNeotetrapoda (total), Tetrapoda (apo), and =
Neotetrapoda (crown), though I don't really want to open up this new =
can =3D
of worms.  Also, remember that it doesn't really make sense to use =
PanTetrapoda for the total clade if Tetrapoda refers to an apomorphy =
clade, as there is not a 1:1 relationship between total and apomorphy=

20 Oct 2004


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