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

[Tim Williams <tijawi@gmail.com>]

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).