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Date: Wed, 20 Oct 2004 12:08:01 -0400
From: [unknown]
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: Re: crown clade convention (long)
David Marjanovic wrote: - Neotetrapoda is not widely known. I am certain that by far most of = those neontologists simply don't know it exists. >That's exactly the problem! They're not going to use poorly known n= ames =3D if they want people to read their papers.< - Tetrapoda has occasionally had a rank (superclass), while Neotetrap= oda =3D has never had one, as far as I know or can imagine. When Neotetrapoda was coined, almost everyone was still concerned with ranks, and preferred= =3D names that had ranks over such that lacked them. This practice still has = =3D effects; even proponents of phylogenetic nomenclature often prefer using widel= y =3D used names over using less widely known but more precise names when they j= ust sketch the outlines of a tree in their texts. >I doubt that many more people would have used the name Neotetrapoda = just =3D because it had a rank.< - Neotetrapoda was coined at a time when very, very little was known = about tetrapod phylogeny. There was no perceived difference between the traditional group and the crown-group -- except for *Ichthyostega* (f= ew people knew the two or three others), about which neontologists simpl= y didn't care. >The number of known taxa outside of the crown is not what's importan= t. =3D Ichthyostega was recognized as being outside of the crown, and that's= the =3D reason that the name Neotetrapoda was proposed. Moreover, neontologi= sts =3D still largely don't care about fossils outside of the crown, even tho= ugh =3D that number has increased in recent years. The problem does not have= to =3D do with the number of such fossils but with the fact that the charact= ers =3D of interest to neontologists often cannot be assessed in those fossil= s. =3D This is exactly the problem: Neontologists don't care about the foss= ils =3D but they do want to use the well known names. Therefore, they common= ly =3D use those names as if they apply to the crowns.< I don't quite understand why we should canonize forever the casual = =3D approach used by many neontologists. The PhyloCode presupposes evolution, afte= r =3D all. To talk about evolution while ignoring fossils is not a good idea. Neontologists are stuck on the 3-dimensional surface of 4-dimensional biology. They usually don't even _need_ the precision that paleontolo= gists need when talking about a phylogenetic tree. >History has already shown that neontologists often ignore the fossil= s =3D even though the names they use supposedly refer to clades that includ= e =3D various fossil taxa outside of the crown, so it doesn't seem that = =3D perpetuating that use of names is going to get them to pay attention = to =3D the fossils. The fact that neontologists don't _need_ the precision = that =3D paleontologists do is precisely the reason that they are unlikely to = adopt =3D the unfamiliar names proposed by paleontologists to make those precis= e =3D distinctions!< This is a good argument [about justified inferences], but perhaps not= as =3D good as it first seems. The real problem, what's really going on here is, I think, the tendency to = =3D generalize =66rom a small subset to an entire clade _with a well-known name_. Th= ere are incidents when features found in living birds, or only in _some_ of t= hose, have been generalized to all of Dinosauria! Perhaps -- I'm just guess= ing here -- the pompous introduction of specific new names for certain (!= ) crown-groups would make the abovementioned neontologists more aware o= f the need to be precise -- in those rather few cases where it is a need in= the first place. Besides, I think that statements about the expression of a gene are = =3D usually not going to lead to a noticeable misrepresentation of the larger-than-crown-croup with the name in question. >History has already shown that this isn't how it works. Names such = as =3D Neoterapoda and Neornithes have already been proposed for crown group= s, =3D but the neontologists don't use them.< (Less important... Tetrapodomorpha is preoccupied by the panstem, the sistergroup of Dipnomorpha which includes the lungfish. Both names ar= e widely used. Like Tetrapoda, Dipnoi has been used for something large= r =3D than the crown-group since the 19th century... oops... fossil lungfish wer= e =3D known before living ones were recognized... so perhaps this isn't a good = =3D example.) >First, earlier defiinitions of Tetrapodomorpha have no status under = the =3D PhyloCode, but even they did, I'm sure we could come up with another = name =3D that made reference to the relevant apomorphy: Tetrapodiformes, Tetr= apodal=3D ia, Holotetrapoda, Acrotetrapoda, or some other name.< I wouldn't say so [about whether paleontologists or neontologists hav= e =3D been more willing to change their use of names]. Lacertilia vs Sauria= =3D seems to be a case of widespread change in the neontological community, like Carinatae vs Neognathae, = the abandonment of Pisces, Anamnia and now even Agnatha, or the surprisin= gly widespread use of Archosauria (which, outside of phylogenetic nomencl= ature,=3D includes only the crocodiles among the living, so it is redundant for neontologists; in PN it also includes the birds). >These examples are not comparable in that they don't have to do with= =3D changing the reference of a widely used name from a more inclusive gr= oup =3D to a crown.< =3D20 This could bear a certain risk that phylogenetic nomenclature is bein= g adapted to what neontologists are _perceived_ to be doing, not what t= hey really _are_ doing... I fear. I'm concerned because very few neontolo= gists have weighed into this debate -- not just on this list or in Paris, b= ut =3D also (to my limited knowledge) in the literature. It's certainly not good = if my fears are true and WE (paleontologists) are talking about THEM. >Well, I am primarily a neontologist, as are Cantino and Donoghue, an= d we =3D also favor the crown convention.< =3D20 I would say that there is rather little neontological literature that= =3D deals with crown-group Mammalia as a whole. The monotremes are much too oft= en either ignored or regarded as curiosities; this has far-reaching consequences because far fewer internodes separate them from the trad= itiona=3D l beginnings of Mammalia than from the last common ancestor of marsupia= ls =3D and placentals. It's sort of the opposite of the situation with the birds= . :-) >No comment (tangential).< The other way around neontologists wouldn't so much have to _change_ = their usages as to make them more precise. Do they mean "Tetrapoda" when th= ey write it? Do they mean "living land vertebrates"? Do they mean anythi= ng in between? I think in many cases they haven't thought about this themse= lves. But in many other cases they have -- and write phrases like "must hav= e =3D been present in the common ancestor of living tetrapods", note "living". >This is certainly possible, though it remains to be seen whether mos= t of =3D them would actually state things more precisely. If the widely known= =3D names refer to the crowns, they will automatically be precise without= =3D having to make an extra effort.< Kevin 20 Oct 2004