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Re: [dinosaur] Latenivenatrix, new troodontid from Dinosaur Park Formation, Alberta (validity of Troodon)

History is replete with taxonomic names that were based on
undiagnostic material, that effectively mean little beyond that they
were named. Names, including *Ceratops* and *Stegosaurus* and
*Allosaurus* have been found again and again to be wanting of
diagnostic quality. Some more than others. For the argument of
stability, for the mere fact that these names appear in old books and
thus _must mean something_, these names have been preserved.

The historian in us agrees: we should not abandon these names for the
sake of their value; but their value is limited to the scope of
history. For the pursuit of science, the names must also mean
something tangible. We've decided diagnostic characters and
differentiation are these best means for providing an objective
measure -- and in that measure, these old names have been weakened,
because the material that supported them was found wanting. Then, what
we do is try to find some _other_ animal that fits our _newer_ idea of
what that animal is, and prop it up. In the argument of "stability"
(the age-old use of names built upon other names in the Linnaean
system), we've kept these aged Nicodemus taxa trucking along.

We have only a vague idea of *Astrodon*'s appearance; specimen drawers
are littered with named scales and teeth whose material extends no
further; and *Troodon formosus* is alive in the spirit of dinosaur
paleo far longer than its brethren named by Joseph Leidy, revived by
the _idea_ that it might be unique stratigraphically ... and for
little other reason.

Despite this, I can agree somewhat about holding off on saying
anythong of *Troodon formosus* should there be a hope of finding
topotypic material. But for all my optimism, I am also a cynic, and I
would rather put aside that which does not serve us (communication,
science, history) for something that does. That does, of course,
depend on what happens to the TMF material. Until then, let us put
aside *Troodon formosus*; while beautiful, it harms us by sustaining
the image of animals removed from it in space and time when we know
these factors have evolutionary meaning.

On Wed, Aug 9, 2017 at 8:28 PM, Tim Williams <tijawi@gmail.com> wrote:
> Jaime Headden <jaimeheadden@gmail.com> wrote:
>> To add to this, there remains doubt as to which tooth position the
>> holotypic tooth derives, with the general region being mroe or less
>> assumed by most authors. The tooth is well-preserved, but it's not
>> terribly distinctive, which impairs almost any diagnostic method one
>> may deem to use *Trodon formosus*. Leaving it to the realm of
>> historical artefact would perhaps be wise. This means the Two Medicine
>> Formation material may be best suited with a new name, if
>> diagnostically supported.
> If a diagnostic troodontid specimen turns up in the Judith River
> Formation that includes teeth that resemble the holotype _Troodon_
> tooth... it's been suggested that this could be referrable to
> _Troodon.  So this specimen could possibly be used to uphold _Troodon_
> as a valid genus.  But I don't think this is the best approach.  I
> agree with you that, because of the nature of the tooth, and the fact
> that the same kind of teeth occur in different troodontids, that
> _Troodon_ is best consigned to history.  (The only alternative is to
> create a neotype based on a diagnostic specimen, which means that the
> original tooth could no longer be called _Troodon_.)
> I'd go one step further and abandon the name Troodontidae as well -
> and revert to using Saurornithoididae as the name for this clade.  I
> know it's permissible to retain family-level taxa founded on nomina
> dubia (we still use Ceratopsidae, after all).  But I still don't think
> it's a good idea (I also think the name Ceratopsidae should be
> abandoned).  As a nomen dubium, _Troodon_ would not be a genuine OTU
> (operational taxonomic unit), and so wouldn't be included in any
> phylogenetic analysis - so its relationships can't be tested.  Also,
> Saurornithoididae was erected explicitly to include _Saurornithoides_
> and _Stenonychosaurus_ (now back from the dead as a valid genus).

Jaime A. Headden
The Bite Stuff: 

"Innocent, unbiased observation is a myth" - P. B. Medawar (1969)