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Re: Typical and less typical types

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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