Message 2001-02-0076: Re: Fwd: Re: Codes

Fri, 16 Feb 2001 22:53:39 +0100 (MET)

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Date: Fri, 16 Feb 2001 22:53:39 +0100 (MET)
From: David Marjanovic <>
Subject: Re: Fwd: Re: Codes

> In another message, David wrote:
> >Group names are not defined at all in the old codes, which is why
> >they can be applied by anyone in any way they see fit, as long as
> >they contain the type species for the group.
> Group names are defined in the old codes, at least operationally, in
> terms of a rank and a type.  For example, Asteraceae is defined as
> the taxon of family rank that includes the type of Aster.

Those above the superfamily level (that aren't explicitely governed by the
ICZN), however, are "defined" much more flexibly, mostly by diagnosing them
and listing their contents. The most recent two examples:

"Systematic palaeontology

Class Mammalia Linnaeus 1758
Subclass Holotheria Wible _et al._ 1995 [I haven't read the paper cited in
this place, but I doubt Holotheria was given a rank]
Infraclass Australosphenida nov.
(Include Monotremata; Ausktribosphenida [monotypic as far as I know =
*Ausktribosphenos nyktos*]; and *Ambondro*).
_Etymology._ [...] [No type taxon.]
_Diagnosis._ Holotherians with tribosphenic molars; differ from
boreosphenidans in having [...]; differ from all non-tribosphenic holotherians in having
a transversely wide talonid; differ from *Shuotherium* [its sister taxon]
[...]; and differ from boreosphenidans (including extant therians) by primitive
retention, at least in *Ausktribosphenos*, of the postdentary trough on the
dentary (also see Supplementary Information).
_Distribution._ Middle Jurassic of Madagascar; Early Cretaceous to recent of
Australian region; Palaeocene of South America. The oldest australosphenidan
is *Ambondro* from the Middle Jurassic of Madagascar.

Infraclass Boreosphenida, nov.
(include Tribosphenida McKenna, 1975 [ = marsupials, placentals and a few
Cretaceous relatives])
_Etymology._ [...] [No type taxon.]
_Revised diagnosis._ Differ from all non-boreosphenidans in [...]; differ
from kueneotheriid holotherians, some eupantotheres and australosphenidans by
absence of [...]; differ from all mammals except Australosphenida by presence
of tribosphenic molars; differ from *Shuotherium* in having [...]; differ
from Australosphenida by having [...] but lacking [...].
_Distribution._ Restricted to the Northern Hemisphere during the Early
Cretaceous; present in latest Cretaceous [or earliest Palaeocene] of South
America, India and northern continents; Tertiary to recent of the world. The oldest
boreosphenidans are Berriasian [Early Cretaceous] in age."

Luo Zhexi ["Zhe-Xi Luo"], Richard L. Cifelli & Zofia Kielan-Jaworowska: Dual
origin of tribosphenic mammals, Nature 409, 53 -- 57 (4 January 2001).
This article includes a cladogram, and lots of cladistic analyses were done
to find the two newly named mono-/holophyletic taxa, so I wonder why ranks
and no definitions were given. These may be the last named taxa without a
phylogenetic definition in vertebrate palaeontology.

> In yet another message, David wrote:
> >Many (the vast majority in my experience, although I realize that I
> >have a biased sample) systematists reject paraphyletic groups now,
> >and only use names that have been given to paraphyletic groups if
> >the group concept is changed to include all the descendants of the
> >common ancestor. That is the same under the old and new codes. I
> >can't remember the last time I heard of someone purposefully
> >supporting the naming or recognition of a paraphyletic group.

There are a few on the Dinosaur Mailing List, very few (2 or so), who want
to have birds as descendants of a paraphyletic Dinosauria.

> I think that zoologists (at least vertebrate zoologists) are ahead of
> other systematists in this regard.

Quite possible.

> I'm sorry to say there is still
> widespread support for paraphyletic groups among plant taxonomists.

The few Nature papers I've seen in the last few years didn't even recognise

> A bigger question that hasn't been addressed at all, though, is how
> species names will be defined under the PhyloCode.  Will they have a
> phylogenetic definition like clade names do and, if so, what form
> will it take?  This, as well as the form that species names should
> take, will have to be resolved before rules for species can be added
> to the PhyloCode.  The Cantino et al. paper considered only the form
> of species names, not the issue of definition.

Does anyone have a better idea than what is currently used: Ernst Mayr's
definition for extant sexually reproducing species, educated guesses based on
the type specimen for all others?
(Seems to work quite well for most fossil vertebrates.)
The current version of the PhyloCode states that clades and species are
fundamentally different things (for example, paraphyletic species must exist), so
I wouldn't try to define species like clades.

> David will argue that in Method M, the combination of the PhyloCode
> name and a taxonomic address looks identical to the Linnaean binomial
> for that species.  This is true, but there is no requirement that a
> taxonomic address be cited or, if one is cited, that it be the genus
> name of the Linnaean binomial.  If Quercus alba is converted to alba
> under Method M, the name is alba.  Period.  Sensible people will
> frequently include the taxonomic address Quercus before the name, but
> there is nothing to stop people from referring to this species solely
> by its name (alba) or from including some other taxonomic address
> such as Fagaceae--another clade to which this species belongs.  It is
> therefore misleading to argue that under Method M, the name is the
> same under both codes.

However, because specific epithets need not be unique under the existing
codes, there are so many identical ones in even closely related genera that
people will practically have to cite the genus name (whatever will happen to
genera under PhyloCode...) -- so far, at least vertebrate palaeontologists put
all their creativity into genus names and none into specific epithets. When I
think of all the nonavian dinosaurs that end in "mongoliensis"... urgh.
Method M will also likely stop people from naming unnecessary monotypic
genera (by far most nonavian dinosaur genera, for example, are monotypic), so
we'll lose a lot of redundancy. I don't see much of a problem in referring to
the dromaeosaurids *Velociraptor mongoliensis* and *Adasaurus mongoliensis* as
*Velociraptorinae mongoliensis* and *Dromaeosaurinae mongoliensis* (apart
from that it sounds odd).

So I'll support Method M. :-)

Maybe the genus names of monotypic genera, rather than their specific
epithets, should be conserved under Method M? This would mean that usage, apart
from the loss of the capital letter, wouldn't change at all.

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