Re: New papers in Geobios (and nomenclatoral gripe)

[Tim Williams <twilliams_alpha@hotmail.com>]

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.

Cheers

Tim