Message 2004-10-0003: Re: REPOST: Crowns, Panstems, and their Correspondence to ea=

Thu, 09 Sep 2004 23:06:32 +0200

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Date: Thu, 09 Sep 2004 23:06:32 +0200
From: [unknown]
To: PML <>
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=
the stem, we could use something like AcroMammalia from the crown and
Mammalia for the stem.  My preference, for reasons outlined in severa=
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=
(as opposed to names).  That is, even if I were to use Mammalia for t=
crown and PanMammalia for the stem, I could still define the names as
PanMammalia =3D Clade (Mammalia [Homo sapiens and Ornithorhynchus ana=
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=
since one wouldn=92t know what name to use for the stem until one had=
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 =
in the convention. Otherwise we will often tempt ourselves to think t=
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=
been suggested, and *Auto-* has been used once (*Autoceta* is the
crown-group of whales -- but probably not defined as a crown-group, j=
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

Besides, what crown-groups are eligible for receiving a panstem? Only=
that have words like "crown-group" or "extant" in the definition? Or =
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

In its other sense (Crustacea + Hexapoda), however, it seems to have =
synonym: Tetraconata Dohle 2001 (abstract:, which Google finds 74=

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=
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=
greatly reduce the size of this problem -- as long as typographic err=
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=
would be to use affixes that had never been used before=97ever, but t=
strategy isn=92t ideal either.

Why not?


Feedback to <> is welcome!