Re: Podokesauridae, Problems of Nomenclature Returned

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Sun, 20 Jan 2002, Jaime A. Headden wrote:

>   It doesn't really matter. Well, sure, in a world where only names that
> had such a definition applied to them this would be true. But this is not
> so, and while definitions allow us to relate taxa to one another,
> Podokesauridae has been used in content for the same clade as
> Coelophysidae.

Has it really? Sereno's definition of _Coelophysidae_ includes
_Procompsognathus_ and _Segisaurus_. Have these ever been included in
Podokesauridae?

Even if they have, there's still the fact that two taxa can have identical
content but different definitions. _Sauropsida_ and _Reptilia_ are not
synonyms at all, although they currently have the same content.

I do not think you can prove to me that Familia Podokesauridae is exactly
the same as Clade _Coelophysidae_.

> It may seem to skid-doodly in getting around some problems, but hey,
> the PhyloCode hasn't been firmly established, and may not for many
> years. Until then, we can use it as recommendations, but it lacks
> authority.

And I do use it as a recommendation. Note that I am not saying that anyone
wanting to follow traditional taxonomy and the ICZN should use
Coelophysidae over Podokesauridae. You are absolutely right that they
should use Podokesauridae (and Parvicursorinae and probably Segnosauria,
although that one isn't mandated). But as far as phylogenetic taxonomy is
concerned, I think that undefined names have no more validity than a
species named without a type specimen.

I know my website doesn't always reflect this philosophy, but I am
changing it to do so in the future.

> <You can't really synonymize undefined taxa because they are not
> explicit.>
>
>   It's very easy to synonymize taxa, simply based on content or inclusion
> of hypodigm.

As I pointed out above, two non-synonymous taxa can have the same content.

> Definition is just another way of doing it, probably preferred by
> some. But why, O why can taxa only be synonymized if the definitions
> are congruent, i.e., homodefinitional?

Well, they can be heterodefinitional (subjective), too -- but for that
they'd both have to be defined.

_____________________________________________________________________________
T. MICHAEL KEESEY
 The Dinosauricon        <http://dinosauricon.com>
  BloodySteak             <http://www.bloodysteak.com>
   personal                <keesey@bigfoot.com> --> <tmk@dinosauricon.com>
    Dinosauricon-related    <dinosaur@dinosauricon.com>
     AOL Instant Messenger   <Ric Blayze>
      ICQ                     <77314901>
       Yahoo! Messenger        <Mighty Odinn>