Re: Suchosaurus, Baryonyx and Martinavis

["T. Michael Keesey" <keesey@gmail.com>]

On 10/2/07, Tim Williams <twilliams_alpha@hotmail.com> wrote:
> I think we've been through this before, though not with _Troodon_ as the 
> casus bellus.  Remember the Great Mochlodon War of 2006? 
> (http://dml.cmnh.org/2006Jun/msg00398.html, and so on...)

I knew it seemed familiar.

> The take-home message is that while the ICZN does not *rule* on nomina dubia, 
> it does have rules concerning higher-level classification when a species does 
> *not* have a valid specimen as its type specimen.

But isn't that a separate matter, to do with the selection of
neotypes? The only instances I see in the ICZN of the word "dubium" is
in articles about the selection of a neotype.

> This is bound up with the principle of hierarchial typification (Article 
> 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."
>
> So to return to the current example... if _Troodon formosus_ is not 
> *taxonomically* valid at the level of species, then the genus is not valid 
> (because of the nature of its type).

But it is taxonomically valid, since it was validly published, isn't it?

Wouldn't this have more to do with species-group names that somehow
did not meet the requirements of publication, thereby being nomina
nuda (and thereby making any genus-group names typified by them nomina
nuda, and any family-group names typified by those genus-group names
nomina nuda)?

>  And if the genus _Troodon_ is not valid, then Troodontidae is not valid (in 
> the nomenclatural sense) because of this step-wise hierarchial typification.  
> In short, a family is tied to its type genus, and a genus is tied to its type 
> species, and a species is tied to its type specimen(s).  But you can't skip a 
> step: it's strictly hierarchial.  So says the ICZN.

Your usage of "valid" (i.e. diagnostic) is not the same as what I
thought the ICZN's usage was (i.e., validly published and not
synonymous).

>From the ICZN's online glossary:
"valid, a. (validity, n.)  Of an available name or a nomenclatural
act: one that is acceptable under the provisions of the Code and, in
the case of a name, which is the correct name of a taxon in an
author's taxonomic judgment."

"[I]n an author's taxonomic judgment." That's pretty vague, but I
think it means judgment concerning synonymy. I.e., a valid name is an
available name that is not also a junior synonym.

Since the holotype specimen is so poor, we can't be very sure whether
_Troodon formosus_ and _Stenonychosaurus inequalis_ are synonyms. If
they are, _T. formosus_ is the valid name. If they aren't, then both
are valid names. In either case, both are available names. In no case
is _T. formosus_ invalid (although it may be a candidate for a
neotype).

(Incidentally, I'm not arguing that this is a *good* system, just that
it is *the* system.)

> When you ask a perfectly reasonable question like "But do they [_Troodon_ and 
> _Stenonychosaurus_] share more recent common ancestry with each other than 
> with _Dromaeosaurus albertensis_ or _Vultur gryphus_?", I agree the answer is 
> "Yes".   But this is irrelevent to the ICZN.

(Although not, of course, to the PhyloCode.)

> IMHO, this is why it is better to completely ignore priority for family-level 
> names and anchor all clades in well-established species (i.e., those with 
> excellent type specimens).

I would disagree in the case of eponymous names. _Ceratops montanus_
might not be well-known, but it should not be permissible for it to be
outside of _Ceratopsidae_.

> If _Troodon_ is declared a nomen dubium, then there's no objective reason to 
> maintain Troodontidae in preference to Saurornithoididae any more than we 
> would use Deinodontidae in preference to Tyrannosauridae.

Isn't _Deinodon_ specifically a nomen oblitum, though?

> I'm happy to retain coordinated family-level names.  But I'd argue for 
> excluding them from the purview of the ICZN.  Let PhyloCode take over 
> families and so forth, with ICZN retaining control of genera and species.

Let's come back to that in a decade or two....

-- 
Mike Keesey