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Date: Wed, 02 May 2001 09:54:48 -0600 (MDT)
From: kinman@usa.net
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: subscribers (& "lophotrochozoans")
Taxonomic suppression? I'm not suppressing anything, nor am I argu=
ing
against formal taxon names (see David Hillis post). But as professionals=
we
have to show some restraint. I recognize formal taxa that have stood the=
test
of time, and I do not arbitrarily discrimate against paraphyletic groups
(although they are small in number compared to the holophyletic groups wh=
ich I
recognize).
And I use {{markers}} to show where exgroups are removed. Paraphyle=
tic
groups with such markers render them holophyletic in an informational sen=
se,
and cladistic sister group information is not discarded as it is in
traditional Linnean classifications. That is why I call my classificatio=
ns
cladisto-eclectic.
48 phyla, 269 classes, 1,719 orders (and an estimated 15,000
families)----I am hardly against the recognition of formal taxa. We need=
them
for communication and a relatively stable evolutionary framework. I do n=
ot
suppress intermediate taxa (even though they are generally less stable), =
but
choose to refer to them with informal names, plus language-neutral schema=
such
as coding and/or cladograms.
Kingdom Metazoa and Phyla Chordata, Echinodermata, Mollusca, etc., t=
hese
are uncontroversial clades that have stood the test of time. These are t=
he
kinds of groups I formally recognize at every level of the Linnean hierar=
chy
(including mammalian orders, although I did emend the endings for reasons=
I
have explained elsewhere).
Lophotrochozoa, on the other hand, is extremely controversial. Nami=
ng
such a formal taxon on a single gene (and a handful of organisms) was
immediately and rightly criticized for various reasons by Conway Morris,
Cohen, Gawthorp, Cavalier-Smith and Winnepennickx (Science, 272:282). =
Hillis claims their are "hundreds" of synapomorphies for Lophotrocho=
sa
(many of which are individual bases in 18S rDNA sequences), but he appare=
ntly
chooses to ignore a vast literature that contradicts that it is a clade. =
And
not surprisingly, the very same molecular analyses do not "strongly" supp=
ort a
deuterostome clade (which is far less controversial). That should have r=
aised
a big red flag.
In my opinion, lophotrochosozoan rDNA is conservative and plesiomorp=
hic,
and that two clades (deuterostomes and ecdysozoans) arose independently f=
rom
it, each having rDNA which diverged from the more conservative
lophotrochosozoan form.
Therefore, I believe erecting a formal clade on very flimsy data was=
not
only premature and unwise (and I'm far from alone in that assessment), bu=
t
that it will continue to confuse and obscure the relationships among
bilaterian phyla. It is undoubtedly a natural paraphyletic taxon, but so=
broad and conservative that it has no particular value, and regarding it =
as a
holophyletic clade will probably be seen as having been very damaging in
retrospect. Cladists should be very concerned when such cladistic
overextrapolation is published (much less formalizing it with a new forma=
l
taxon name), and I worry that this casts a cloud over cladistic analysis =
in
the long term. I would not even recommend the regular use of the informa=
l
"lophotrochozoan"--- it is far preferable to refer to them separately as
trochozoans (or the slightly more inclusive spiralians?) and lophophorate=
s.
--------Ken Kinman
P.S. As for Rodentiformes and Lagomorphiformes, I am convinced they do f=
orm a
glires clade (and continue to code them as such). I would certainly neve=
r
combine two such useful and stable taxa into a formal Gliriformes. A car=
eful
reading of my example bears this out.
*****************************************
"Jaime A. Headden" <qilongia@yahoo.com> wrote:
Ken Kinman (kinman@usa.net) wrote:
<I see no great need for formal taxa Theropoda, Coelurosauria,
Maniraptora, etc., when informal names (theropods, coelurosaurs,
maniraptors, etc.) suffice. If Lophotrochozoa is a synonym of
Bilateralia, as I believe it is, I certainly hope Bilateralia
was cladistically defined first, so that it will have priority.
=2E....
Do we really need formal taxa Altungulata, Pseudoungulata,
Uranotheria, Behemota, Tethytheria, Afrotheria, Cetartiodactyla
(=3D Eparctocyona ?), or even "oldies" like Glires and Archonta.
=2E.....
Uniramia is as dead as a doornail as far as I am concern, but I
betcha somebody's going to give it a formal cladistic
definition.>
Do we have validations for these statements of taxonomic supression?
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