Re: New papers in Geobios (and nomenclatoral gripe)

[Tim Williams <twilliams_alpha@hotmail.com>]

T. Michael Keesey wrote:

> Tim, it seems to me that you're invoking an ICZN rule (validity of a genus 
> depends on validity of its type species) and then trying to apply a concept 
> which is *external* to the ICZN (the concept of
> "dubious names").

The ICZN does recognize the concept of a _nomen dubium_ - as a taxonomic 
concept that is relevant to nomenclature.  That's one reason why the ICZN 
allows for the designation of a neotype under exceptional circumstances 
(Article 75).  The term "nomen dubium" is mentioned in 75.5. (Replacement of 
unidentifiable name-bearing type by a neotype.)

> Now, under the ICZN, _Mochlodon_ is simply defined as the genus that 
> includes _M. suessi_, so you can't objectively say whether it's a synonym 
> of _Zalmoxes_. But if you yourself subjectively consider the group that 
> includes the type specimens of _Z. robustus_ and _M. suessi_ to be a 
> "genus", then the name for that group has to be _Mochlodon_, by ICZN rules. 
> Never mind that we can't tell whether the species are synonyms or not--the 
> ICZN doesn't care.

Yes, there are two competing arguments here:

(1) The genus that includes the type material for _M. suessi_, _Z. robustus_ 
and _Z. shqiperorum_ should be called _Mochlodon_ because _Mochlodon_ was 
named before _Zalmoxes_.  As long as the genus can be demonstrated to 
include the _M. suessi_ type, the genus must be called _Mochlodon_ (as the 
oldest available name) since it includes the type specimen for _M. suessi_.

(2) The taxonomic identity of _M. suessi_ cannot be determined at the 
species level based on the existing name-bearing type.  _Mochlodon_ is 
defined objectively by _M. suessi_, which is in turn defined objectively by 
its type.  Because the type for _M. suessi_ could belong to either of the 
two named _Zalmoxes_ species (_Z. robustus_ and _Z. shqiperorum_), the 
taxonomic identity of _M. suessi_ is indeterminate.

You are arguing (1).  I am arguing (2), based on 61.1.2.

"Objectivity provided by typification is continuous through the hierarchy of 
names. It extends in ascending order from the species group to the family 
group. Thus the name-bearing type of a nominal species-group taxon is a 
specimen or a set of specimens (a holotype, lectotype, neotype or syntypes 
[Art. 72.1.2]), that of a nominal genus-group taxon is a nominal species 
defined objectively by its type; that of a nominal family-group taxon is the 
nominal genus on which its name is based."

Mike, if I understand you correctly, you are arguing that because the type 
specimens of _Z. robustus_ and _M. suessi_ belong in the same genus, then 
_Mochlodon_ has priority because it was named before _Zalmoxes_.  But in 
doing this you are cutting out the middleman: the type species.  The ICZN is 
strictly hierarchial on this point.  My interpretation of 61.1.2. is that a 
GENUS is typified directly by its SPECIES, not by the TYPE.  This is what I 
meant when I said that a genus is as only as good as its type species.

Confused?  I am.  But I think what the ICZN is getting at is that you can't 
use type specimens to typify genera (or families) directly; you have to have 
a type specimen that typifies the species, and the species then typifies the 
genus, and the genus then typifies the family.  Type specimens can only be 
used to establish a species (72.1.1.), and a type species is used to 
establish a genus; but a genus cannot be established directly upon the type 
specimen of its type species.

In our example, that means that the type specimen for _M. suessi_ cannot be 
used to typify _Mochlodon_; you have to use the type specimen to typify _M. 
suessi_, and then use _M. suessi_ to typify _Mochlodon_.  But because _M. 
suessi_ cannot be identified to the level of species, there is a break in 
the chain and we can't go any further in the hierachy.

In another example, if the type specimens of _Antrodemus valens_, 
_Allosaurus fragilis_ and _Saurophaganax maximus_ could be demonstrated to 
belong in the same genus, using your argument we would get _Antrodemus 
fragilis_ and _Antrodemus maximus_, even if _Antrodemus valens_ is a nomen 
dubium.

> I'm getting this impression of the phylogeny:
>
> --+--outgroup
>  `--+  [incertae sedis] M. suessi (?=Z. robustus; ?=Z. shqiperorum)
>     |--Z. robustus
>     `--Z. shqiperorum

No, because _M. suessi_ cannot be identified at the level of species.  Your 
phylogeny seems to reflect this, but _M. suessi_ is not a "species" in the 
taxonomic sense, only in the nominal sense.  I'll ask you this question: if 
_Z. robustus_ and _Z. shqiperorum_ are referred to _Mochlodon_, what is the 
type species for _Mochlodon_?

> The _Iguanodon_ example doesn't apply here because it's a special case. The 
> ICZN invalidated _I. anglicum_ by fiat. Perhaps they could do so for 
> _Mochlodon_ and _M. suessi_ as well, but they haven't, yet.

The _Iguanodon_ example does apply, because _I. anglicus_ was replaced as 
the type species because, as a nomen dubium, it could not be identified 
taxonomically at the species level.  When agreeing to designate a neotype, 
the ICZN was acting in the name of nomenclatural stability.  You could not 
have the type species (_I. anglicus_) as a nomen dubium AND have _Iguanodon_ 
as a valid genus (in the taxonomic sense).  So in order to save _Iguanodon_, 
_I. bernissartensis_ got the gig as the new type species.

Cheers

Tim