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Re: Coelophysis/Rioarribasaurus



Dinogeorge wrote (date/time?):

>Subsequently it has been suggested on the basis of obdurator
>foramen differences that there are probably 3 genera of small
>theropods at Ghost Ranch (Coelophysis, Rioarribasaurus and
>Syntarsus).

Why should the obturator foramen be so important?  How variable is it in
large populations of coelophysids, especially in populations from
different locations?  On what basis SHOULD coelophysid genera be
distinguished, and why?  Why not establish three _species_ differentiated
on the basis of obturator foramen?:

                        _Coelophysis bauri_
                       "_Coelophysis euobturator_"
                       "_Coelophysis oddobturator_"

I'll bet that the mythical "Coelophysis obturator_" comes in three
variants of the fourth trochanter--acute, obtuse, and pendant.  Should we
therefore have two more species or two more genera?  How about just three
subspecies?

>As far as I know, _Coelophysis_ itself has not been identified at
>Ghost Ranch (except by Colbert and those who agree with him, of
>course).

Wait a minute!  Colbert identified it there FIRST, and that's what it was
called for decades!  "Except by...those who agree with him," you say.
But there were ONLY people who agreed with him for over 40 years!

>Bob Sullivan is working on a new diagnosis for _Coelophysis_ that
>distinguishes it from the Ghost Ranch theropods.

He could just as easily formulate a diagnosis to make all of the Ghost
Ranch theropods into _Coelophysis_.

>Presently, we are free to use either _Coelophysis_ or
>_Rioarribasaurus_ for the Ghost Ranch theropods.

See?

I admit that I am not an expert on coelophysids, so I won't continue on
this crusade, which I fear is lost, anyway.  My point is (and see my
previous posting in response to Bob Myers) that this situation is
unnecessarily complicated, and could have been handled better.  Why not
plan to handle similar situations in the future differently?  PLAN is the
operative word in that suggestion--remove the elements of chaos and
coersion.  Hunt and Lucas might have discussed their findings with
Colbert, and they could have issued a joint paper, or two papers
back-to-back, discussing the issue.  In absence of that, Hunt and Lucas
could have announced beforehand that they planned to establish a new
genus for the Ghost Ranch material, and their justification.  It might
have been good to get all the type material together and made available
for direct comparison by anyone interested--perhaps at a special session
at an SVP meeting.  With feedback from the paleontological community, the
perceived best course of action could have been taken that might have
avoided much or all of the confusion and other adverse effects caused by
decisions made by a relatively small group of people, announced as a
_fait accompli_.


*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu