RE: Ceratops (was RE: Pterosaur diversity (was: Re: Waimanu))

[mike@miketaylor.org.uk (Mike Taylor)]

Tim Williams writes:
>> 1. I think everyone agrees that, based on the type material,
>> _Titanosaurus indicus_ is not diagnosable from other titanosaurs,
>> so that species, which it was once valid, is now a nomen dubium.
> 
> I'm not sure I'm convinced that _Titanosaurus indicus_ is a nomen
> dubium.  It all depends if you limit the name _Titanosaurus indicus_
> to the type material only.

... as I explicitly did (see above).  But is this really something we
have a choice about?  I know that people do diagnose taxa from
non-type specimens, but it's not really on ... is it?  Or is it?

>> I think it's important that this change has happened not because of
>> a change in attitude to the original material, but a change in the
>> context in which it's evaluated, i.e. we now have dozens of
>> sauropods with procoelous caudals, so that this character is no
>> longer diagnostic.
> 
> Yep.  But even the type mid-caudals for _T. indicus_ show characters
> other than just procoely.  The caudals are distinctive, but perhaps
> not diagnostic.

Well, here's (another) problem raised by the complexity of the ICZN.
I guess most people would agree(*) that the _T. indicus_ material is
not diagnostic "to the species level".  ICZN rules of course then
state that this conclusion brings the genus down, too, even if the
type material _is_ diagnostic to the genus level.  That's weird, isn't
it?

(*) You'd think I'd have learned by now not to use that phrase,
wouldn't you?  :-)

>> It is clear that no article of the draft PhyloCode prevents us from
>> continuing to use Titanosauria.  But I still feel a bit queasy
>> about it -- maybe because I am offended that different rules seem
>> to govern Titanosauria and Titanosauridae.
> 
> I'm perfectly at peace with this.  I'm also OK with Ceratopsia
> persisting as a clade even if _Ceratops_ is a nomen dubium.

To clarify, the thing I feel queasy about is not that Titanosauria is
still OK (and please stop messing with my mind my introducing
non-sauropod examples :-) -- it's that different rules seem to govern
Titanosauria and Titanosauridae.  It's the magic in those four letters
"idae" that offends me.

Truly, "idae" is a four-letter word.

> I guess the reason I feel this way is that -idae does have a
> specific meaning, and it should be mandatory that the eponymous
> genus is included.  In other words, -idae is not an arbitrary suffix
> the way -ia is.

Really?  There is nothing in the PhyloCode itself that makes a special
case of "idae" (nor for any other spelling convention).  And we are
talking about phylogenetic definitions here, aren't we?  (Or maybe you
aren't: maybe that's the wrong assumption I've made that has resulted
in our disagreeing.)  In any case, the meta-problem is that, whatever
the PhyloCode actually _says_, the practicalities are that it is
nevertheless circumscribed in how it can govern "idae" names.

>> In my fantasy world, the ICZN continues to govern species and
>> genera, and the PhyloCode foreswears all intention of messing with
>> them.  In return, the ICZN gives up families and the related ranks,
>> leaving the PhyloCode free to govern all clade-names without
>> interference, irrespective of their endings.  But, hey, that's just
>> _my_ fantasy.
> 
> No, it's my fantasy too.  At least with respect to the respective 
> jurisdictions of ICZN versus PhyloCode.

Aha!  So you're OK with genera continuing to exist, and be governed by
the ICZN?  (I thought I was out on a limb there.)

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor  <mike@miketaylor.org.uk>  http://www.miketaylor.org.uk
)_v__/\  "I respect the brainwork behind Z39.50 tremendously [...] but
         Explain is very clearly the result of some terrible mass
         psychosis.  It is broken" -- Sebastian Hammer.