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Date: Thu, 09 Sep 2004 23:06:32 +0200
To: PML <email@example.com>
Subject: Re: REPOST: Crowns, Panstems, and their Correspondence to ea=
----- Original Message ----- =46rom: "Kevin de Queiroz" <Dequeiroz.Kevin@NMNH.SI.EDU> Sent: Thursday, September 09, 2004 9:40 PM >> For example, rather than using Mammalia for the crown and PanMammalia= for the stem, we could use something like AcroMammalia from the crown and Mammalia for the stem. My preference, for reasons outlined in severa= l papers, is the former (i.e., Mammalia and PanMammalia). However, thi= s does not mean that I prefer the primacy of crowns when it comes to definit= ions (as opposed to names). That is, even if I were to use Mammalia for t= he crown and PanMammalia for the stem, I could still define the names as follows: PanMammalia =3D Clade (Mammalia [Homo sapiens and Ornithorhynchus ana= tinus] not Reptilia [Testudo graeca and Lacerta agilis]) Mammalia =3D Clade (extant PanMammalia). Of course, this approach pretty much forces one to name the clades in= pairs, since one wouldn=92t know what name to use for the stem until one had= decided on a name for the crown, but as I said above, perhaps naming these cl= ades in pairs is a good idea. << I think that _if_ the *Pan-* convention will get adopted as a rule or recommendation, _then_ we should probably include a prefix for crown = groups in the convention. Otherwise we will often tempt ourselves to think t= hat everything (or at least everything that we think is a well-known name= ) that lacks that prefix were a crown-group. *Corono-*, *Neo-* and *Acro-* h= ave been suggested, and *Auto-* has been used once (*Autoceta* is the crown-group of whales -- but probably not defined as a crown-group, j= ust happening to have extant specifiers -- if any); *Acro-* may be the be= st idea of those (it's short and hasn't been used for something else yet). That said, while eliminating some confusion, a prefix for crown-group= s could produce new confusion. If both *PanMammalia* and *AcroMammalia* exist= , do we know whether *Mammalia* exists? *Mammalia* could be node- or stem-bas= ed with a fossil specifier, or it could be apomorphy-based, or it could not e= xist at all. Besides, what crown-groups are eligible for receiving a panstem? Only= those that have words like "crown-group" or "extant" in the definition? Or = all node-based clades that happen to have only extant specifiers? >> As far as I can tell, the original authors of the name Pan-Crustacea (Walossek and M=FCller, 1990) did use that name for the total clade/p= anstem of Crustacea. << In its other sense (Crustacea + Hexapoda), however, it seems to have = a synonym: Tetraconata Dohle 2001 (abstract: http://ann.sef.free.fr/fasc37-1-2.html#85-103), which Google finds 74= times. >> You=92re right about Panarthropoda (Nielsen, 1995). That name would= have to be redefined so that it applied to the total clade of Arthropoda (rem= ember, the PhyloCode is not retroactive). << Personally, I like that name better than the *Pan-* convention, becau= se it evokes the concept of "everything that has ever been classified as Arthropoda". (Like Holotheria, "the whole Theria", which corresponds = to the maximum use of Theria sensu latissimo, and is _much_ bigger than the crown-group Theria [in widespread use today], even bigger than the crown-group Mammalia and several other clades to which the latter nam= e has been applied!) But of course, double capitalization or any other method woul= d greatly reduce the size of this problem -- as long as typographic err= ors, and _assumptions_ of typos in others' works, won't become too common. >> To achieve a unified system, some names, such as this one, would have= to be defined differently than originally used. The only way around this p= roblem would be to use affixes that had never been used before=97ever, but t= his strategy isn=92t ideal either. << Why not?