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Re: TROODON, FABROSAURUS AND TOOTH TAXA IN GENERAL



Dinogeorge@aol.com wrote:
> In a message dated 97-09-02 13:50:56 EDT, martz@holly.ColoState.EDU (Jeffrey
> Martz) writes:
> 
> << However, this is not the case with _Troodon_, or for
>  that matter, _Aublysodon_.  The teeth are very unusual and derived, and in
>  the absense of any other cranial material from different species with such
>  teeth, diagnosing taxa with them is no more strange then assigning
>  ceratopsian species based on fairly complete skull material, but lacking
>  postcrania.  One could make the assertation that an isolated ceratopsian
>  skull should not be lumped with a complete ceratopsian skeleton with a
>  identical skull because later discoveries could reveal a species with
>  identical skulls, but very different postcrania.  New discoveries can
>  always change things, but _Troodon_ and _Aublysodon_ teeth are very
>  unusual, and for the time being they seem to be diagnostic. >>
> 
> Alas, _Aublysodon_ teeth are no longer diagnostic. There's little doubt in my
> mind (at any rate) that such teeth (unserrated carinae, D-shaped
> cross-section) are characteristic of a whole subfamily of tyrannosaurids.
> Certainly _Stygivenator_ and the unnamed Oklahoma "Aublysodon" represent
> different genera, but each has the characteristic _Aublysodon_ premaxillary
> teeth, as far as we know. _Alectrosaurus_ also has _Aublysodon_-like
> premaxillary teeth. _Aublysodon_-like teeth, of several different size
> grades, occur in many Late Cretaceous strata in western North America and
> eastern Asia; it is no longer conceivable that a single dinosaur genus is
> responsible for all these occurrences.
> 
        _Aublysodon_ teeth are not diagnostic?  Really?  OK, so where is 
this published?  A), is there enough data for this hypothesis to be 
considered valid and testable, and B), by which method have you tested it?

        As far as your (George) hypothesis (I assume that you have 
analized this enough to determine that it IS a testable hypothesis...) 
concerning the lack of denticles on what you are calling lateral carinae 
on the premaxillary teeth of _Aublysodon_, where do my cf. _Aublysodon_ 
premaxillary teeth with denticulate carinae fit into this scheme.  How 
many specimens have you used in your test of your hypothesis?

        Also, just to play Devil's Advocate, I would say to both Jeff and 
George, just exactly what are you calling "diagnostic" about any of these 
teeth and has this hypothesis been tested and by what method?  
_Aublysodon_ sp. teeth are unusual, yes, but just what is diagnostic 
about them?  Position and possession/lack/shape of denticles?  Is this 
diagnostic for theropod dentition?  Can you prove it?  Before we can say 
that teeth are not diagnostic or are diagnostic, work needs to be done 
on what is or isn't diagnostic about them and why.  This is a rather 
large project that has not been done yet for any dinosaur taxon.


        As for you point about it being inconceivable for a single 
dinosaurian genus to produce such an abundance of teeth across such a 
large paleogeographic (indeed geographic) area, why not (this is NOT to 
say that I agree or dissagree with you, I am just saying that you have 
dropped a rather large speculation out here, and do you have any evidence 
to back up the claim)?

        This falls very close to the nasty border of discussing exactly 
what is a dinosaurian genus in the first place; something that would be 
very interesting, but probably also very frustrating to discuss in this 
forum.

        What sort of synapse-firing does this provoke in either of your minds?

-Josh


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Josh Smith
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