[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Alamosaurus as biggest North American sauropod
I think in these situations the correct thing to do is designate a
neotype. If T. rex is non-diagnostic relative new new taxa A and B,
as long as both are from roughly the same stratigraphic horizon and
geographic location, then pick one--it doesn't really matter which.
This is what the ICZN recommends be done for all nomina dubia
Only when necessary, and only by the Commission.
Brackets are in the original, all emphasis is italics in the original.
Note "may request" in Art. 75.5 and "should [...] request" in Art. 75.6.
>
75.5. Replacement of unidentifiable name-bearing type by a neotype. When
an author considers that the taxonomic identity of a nominal
species-group taxon cannot be determined from its existing name-bearing
type (i.e. its name is a _nomen dubium_), and stability or universality
are threatened thereby, the author may request the Commission to set
aside under its plenary power [Art. 81] the existing name-bearing type
and designate a neotype.
Example. The holotype of the ammonite species *Cycloceras laevigatum*
M'Coy, 1844 lacked important diagnostic features. Upon request the
Commission under its plenary power set aside the type status of this
specimen and designated a neotype (Opinion 1720 (1993)).
75.6. Conservation of prevailing usage by a neotype. When an author
discovers that the existing name-bearing type of a nominal species-group
taxon is not in taxonomic accord with the prevailing usage of names and
stability or universality is threatened thereby, he or she should
maintain prevailing usage [Art. 82] and request the Commission to set
aside under its plenary power [Art. 81] the existing name-bearing type
and designate a neotype.
Example. On discovering that the only existing type specimen of *Aradus
caucasicus* Kolenati, 1857 (Heteroptera) was a specimen of another
species, Kerzhner & Heiss (1993) proposed that the prevailing usage of
the names of both species should be conserved by the designation of a
neotype for *A. caucasicus* under the Commission's plenary power, and
this was accepted in Opinion 1783 (1994).
<<
http://www.nhm.ac.uk/hosted-sites/iczn/code/includes/page.jsp?article=75
If you're not the Commission, you may only designate a neotype for a
species or subspecies if and only if the previous type has been
destroyed or lost _and_ if and only if that species has "an exceptional
need" (Art. 75.3) for a type. And even then Recommendation 75B says you
"should be satisfied that the proposed designation does not arouse
serious objection from other specialists in the group in question"
before you publish.
Most of what most people, likely including myself, believe they know
about the ICZN is wrong.
and I can't think of any better alternatives. However, I have seldom
ever seen this applied, except in the case of Coelophysis bauri. It's
often mis-applied, as in the case of Iguanodon, where rather than
assign a neotype for the species I. anglicus, a new type species was
chosen, probably unrelated to the original, and from a different
geographic location and stratigraphic horizon.
When the Commission does it, it's not a misapplication.
:-)
In related cases like Titanosaurus, the new, better specimens from
the same horizon, if they could not be differentiated from T.
indicus, should have been made the neotype of that species, rather
than become the basis of a new taxon which is almost certainly but
unprovably its synonym. If, later, this is contradicted by evidence
that the original material WAS distinct, or not really referable to
the neotype, well then so be it (IIRC this happened with
Ceoplophysis as well).
The story of the silesaurid *Eucoelophysis* is more complicated than
that, but I'm not sure I remember the details and can't look them up now.