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Re: New papers in Geobios (and nomenclatoral gripe)

Christopher Taylor wrote:

This is simply not true. The recognition of a taxon as a _nomen dubium_ is a subjective, not objective, decision. Nomina dubia retain full taxonomic availability, though they may not currently be
practically usable.

I agree that the recognition of a taxon as a nomen dubium is subjective. For example, there are names that have been revived as valid genera or species after previously being declared nomina dubia. But although a nomen dubium is taxonomically available, its status as a nomen dubium (or nomen vanum) removes it from taxonomy for all practical purposes.

Having a species declared a nomen dubium means that the species cannot be diagnosed at the level of species. If the species in question is the type species for a genus, then that genus is invalid as well. A genus is only as good as its type species. This may seem a little unfair, as the genus may otherwise be very well known and/or include species that are indisputably valid.

The only way to bypass this situation is to designate a new type species, as was done with _Iguanodon_. The original type species (_I. anglicus_) was a nomen dubium, which technically made _Iguanodon_ a nome dubium too. But the ICZN allowed a new type species to be designated (_I. bernissartensis_), which 'rescued' the genus _Iguanodon_ from oblivion. If your premise was correct (i.e., a genus is valid even if the type species is specifically non-diagnostic), then we would not have had to go to all this trouble for _Iguanodon_.

If the taxon can still be diagnosed at the genus level, then there is no reason why the genus should be invalid.

Unfortunately, having an invalid type species is one reason why a genus can be taxonomically invalid.

Then if the _nomen dubium_ is type of a genus, then it may be the appropriate name of the genus that it can be identified to. [snip]
If _Mochlodon_ can be identified at genus level, then _Mochlodon_ is the appropriate name for a genus, whether its type species can be identified at species level or not.

I wondered about this... but again I cannot see how _Mochlodon_ can be valid without _M. suessi_ also being valid. The validity of _Mochlodon_ is predicated upon _M. suessi_ (its type species) not being a nomen dubium. If _M. suessi_ can be demonstrated to be synonymous with one of the _Zalmoxes_ species, then _Mochlodon_ is back in the game, and it would have priority over _Zalmoxes_. But as a nomen dubium, the name _M. suessi_ is limited to the type material; further material cannot be referred to it, and it cannot be referred to another species or genus.

All is not lost for _Mochlodon_. If the two current _Zalmoxes_ species (_Z. robustus_, _Z. shqiperorum_) are shown to be synonymous AND _M. suessi_ belongs to the same genus as _Zalmoxes_, then _Zalmoxes_ becomes a junior synonym of _Mochlodon_. This is because the characters previously use to diagnose the genus are now the same as those used to diagnose a single species, and so _M. suessi_ would become specifically diagnosable.

But if _Denversaurus_ had priority over _Edmontonia_, then it would become the appropriate name for the genus. If _Denversaurus_ does not have priority, then that example is not relevant to the argument at hand. (Because genus- and species-level names are not concordant in the ICZN, there are no requirements for publication of new combinations - in contrast, offhand, to the CBN).

I brought up this example, because of Mickey's argument that _M. suessi_ is referrable to the genus _Zalmoxes_. As he put it:

"If Mochlodon suessi's holotype is referrable to Zalmoxes but not specifically diagnostic, there should be three species of Mochlodon - M. robustus, M. shqiperorum and M. suessi. The latter could be the holotype yet still be specifically indeterminate."

But a species that is specifically indeterminate cannot be a valid species in ANY genus. In this respect, _Denversaurus schlessmanni_/_Edmontonia_ is analogous to _M. suessi_/_Zalmoxes_.

I hope some of that made sense.