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Date: Wed, 20 Oct 2004 14:34:45 -0400
From: [unknown]
To: phylocode@ouvaxa.cats.ohiou.edu
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 time when such an idea didn't exist beyond the statement "first associatio= n of =3D a name with a clade" (as I recall). Given that principle at the time, I= =3D still find it odd that Gauthier et al. would ignore Gaffney's association o= f Neotetrapoda with the crown. Had they followed his first use of this = name associated with that clade, we wouldn't be having this discussion, be= cause 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 = =3D names! See page 106.< In the context of the opinions of the late 80s, I am pretty sure that= most biologists didn't adopt the name Neotetrapoda because they didn't see= the 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 = =3D Amniota (or Tetrapoda), although in that text he certainly recognized its rea= lity, 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= iple redundancies. Amniota and Tetrapoda in Carroll's view are ways of gro= uping classes (explicitly recognizing their singular evolutionary origin, = =3D Carroll, 1988, p.16). And in my opinion this is the root of the imprecision in= =3D usage of most nonsystematists today. As we are more successful and the Phyl= oCode is considered more thoroughly, folks will become better educated abou= t the importance of tree thinking, and overall consistency will be achieved= . =3D That is why I speak about abrogating our responsibility; most biologists a= re still deep in Evolutionary Taxonomy. By accommodating the errors crea= ted =3D by 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= es.< (Sorry--my copy of the 1990 paper is buried somewhere and I am going = =66rom memory) >(Perhaps you're confusing our paper with one by Harold Bryant.)< =3D20 As Michel pointed out, Tetrapodomorpha is imprecise, including porole= piform=3D , osteolepiform, and panterichthyd fishes. I would not expect it to pr= ove =3D an 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= sed imprecisely: let me state it. You must assume "tetrapod" is equivalen= t to "member of Tetrapoda", as Michel did in the Point-Counterpoint, which= was 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 Phil, one of the foremost thinkers about taxonomy and nomenclature, only TH= IS MORNING decided that "tetrapod" probably isn't a real vernacular word= --but 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 = =3D concern ourselves with vernacular names, since the PhyloCode only = =3D 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 = =3D (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 = the debate paper that stating "extant tetrapods express gene Y" is redund= ant because it cannot be anything else, and some editors might actively e= xcise "extant" from that statement. Some authors do state "extant" explicit= ly (most don't), but I certainly would never be fooled into thinking tha= t =3D that statement can be generalized to the entire clade. Has communication b= een 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= ld explicitly state whatever finding is a characteristic of Tetrapoda, a= name that only a vanishingly small group use in their papers (from my anal= ysis =3D of a portion of Michel's literature survey). In fact, most of the exampl= es =3D 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= CZN sense.=3D20 >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 = =3D 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 = =3D 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 manner.< Yes there is imprecision. I believe it is due to the dominance of Evo= Tax, and it is corrected by pushing the advantages of tree thinking. What = these authors do is say "tetrapods express Y and fish express Z", informal = and highly inaccurate (when "fish" really means Danio and "tetrapods" mea= ns Xenopus and Mus) yes, but discussions about character state distribut= ions across clades they are not, so we should not treat them as such. We c= an't even be sure these statements apply across the crown. We should, howe= ver, get authors and editors thinking about these issues. >We all recognize the problems of limited sampling, but more taxa are= =3D 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 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= other reason for imprecision in name use could come from the still dominant paradigm of Evolutionary Taxonomy, which doesn't value tree thinking = as 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 = =3D 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 I need to continue thinking about how overall consistency of use will b= e =3D 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. >Great. I can guarantee you that your position is being considered = =3D 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 = =3D PanTetrapoda (total), Tetrapodiformes (apo), and Tetrapoda (crown) se= ems =3D cleaner than the set PanNeotetrapoda (total), Tetrapoda (apo), and = =3D 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 = =3D PanTetrapoda for the total clade if Tetrapoda refers to an apomorphy = =3D clade, as there is not a 1:1 relationship between total and apomorphy= =3D clades.< Kevin 20 Oct 2004