[Previous by date - Re: RE: crown clade convention]
[Next by date - Re: crown clade convention (long)]
[Previous by subject - RE: RE: a comment on ancestor]
[Next by subject - RE: REPOST: Crowns, Panstems, and their Correspondence to ea=]
Date: Tue, 19 Oct 2004 17:07:59 -0700
From: [unknown]
To: 'Kevin de Queiroz' <Dequeiroz.Kevin@NMNH.SI.EDU>, "'phylocode@ouvaxa.cats.ohiou.edu'" <phylocode@ouvaxa.cats.ohiou.edu=
Subject: RE: RE: crown clade convention
> A few responses to Jason's comments. My responses are in > <. Unfortunately my emailer does things oppositely. =20 > >The same is true for Neornithes, coined for the bird crown clade. > Neontologists hardly ever use this name even when it is the appropr= iate > 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= either > Gauthier or Rowe, who were relative newcomers at the time. (Aside:= I > don't remember arguing that apomorphy-based definitions were proble= matic > 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= 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). 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 = 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, C= arroll, 1988, p.16). And in my opinion this is the root of the imprecision in= 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= . That is why I speak about abrogating our responsibility; most biologists a= re 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 = =66rom memory) =20 > >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 = the > 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= on-- > e.g., "tetrapods express gene y") but the fact that less well know = names > coined specifically for the crowns (e.g., Neotetrapoda) are consist= ently > avoided by neontologists in precisely those situations when it woul= d be > appropriate to use them.< =20 As Michel pointed out, Tetrapodomorpha is imprecise, including porole= piform, 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= 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= . 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? 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 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 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= CZN sense.=20 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. > 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= s, > including in the neontological literature. Obviously biologists hav= e a lot > to say about this group (which they call "Tetrapoda"). >=20 > >I didn't mean to imply that people didn't have much to say about t= he > 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= f > characters that are not commonly preserved in fossils (e.g., about = genes, > gene expression, physiology, behavior, etc.) and therefore it makes= sense > to use the best known names for those clades. In fact, this is bas= ically > the reason that the widely known names are commonly used imprecisel= y. 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= 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). > There are many statements that neontologists want to make (i.e., ab= out > rarely fossilized characters) that are justifiable only if interpre= ted as > statements about the crown; however, neontologists also want to use= the > widely known names. Therefore, they use the widelly known names AS= IF > those names refer to the crowns despite the fact that those names a= re > 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= names > 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= hat > we're asking is for Jason and other paleontologists to consider cha= nging > their otherwise logical and traditional use of names to achieve gre= ater > overall consistency of use. I realize that this is a big favor to = ask, > 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