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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? __________________________________ ____________________________________________________________________ Get free email and a permanent address at http://www.netaddress.com/?N=3D= 1