Re: Typical and less typical types

[Tim Williams <twilliams_alpha@hotmail.com>]

Christopher Taylor wrote:

>     As such, the term "nomen dubium" (while very useful) has no actual
> nomenclatorial status

You are right; the decision of what to call a _nomen dubium_ is subjective, 
but not arbitrary.  The case of _Antrodemus valens_ versus _Allosaurus 
fragilis_ is a good example.  Because of the 'shonkiness' of the _Antrodemus 
valens_ type material (a partial caudal vertebra), this taxon cannot be 
diagnosed at the species level.  Thus, it cannot be determined whether _A. 
valens_ is conspecific with the holotype of _A. fragilis_ to the exclusion 
of a third taxon.

> There decision that a species
> is unidentifiable is a subjective one by the researchers, and others may
> differ in opinion.

Yes.  The same is true of subjective synonyms, which are likewise often in 
the eye of the beholder.  For example, although almost everyone regards 
_Brontosaurus_ as a subjective synonym of _Apatosaurus_, there is no metric 
for determining whether one genus should be sunk into another.  Objective 
synonyms are different, and occur when two genera or species have the same 
type specimen.

>     As such, a so-called "nomen dubium" still remains available for 
> purposes
> of priority, homonymy, etc.

Yes.  And it is unfortunate that some cool generic names were 'blown' on 
lousy specimens.

> Also, a rejected name can never be resurrected except by a
> second decision by the ICZN (I don't know of any case where this has
> happened, though).

I know of one such case: the shark genus _Carcharias_ was reinstated by the 
ICZN in 1987, reversing an earlier decision to suppress the genus in favor 
of _Odontaspis_.

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