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Every time there is a new posting on this subject everything seems to get
even more confused. Here is my understanding - please tell me if I am wrong
and why (no opinions, please - just facts and refs if necessary!!)
Re-examination of Coelophysis indicated that the type specimen was
undiagnostic. In a letter to Bull Soc Zool Nomenclature mid 1995 a formal
proposal was put to retain Coleophysis for the type material and re-name all
other referred Coelophysis material as Rioarribasaurus. 10-15 submissions
followed from various authors, about 50-50 in favour of the proposal or a
counter-proposal to retain Coelophysis. The last time I checked through BSZN
in Feb this year the ICZN committee had not yet published a decision.
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).I think the suggestion
was that the Coelophysis referred to here was not the type material but
other referred Coelophysis that was different from Rioarribasaurus.
If the above is correct, a number of possible outcomes result.
As the original proposal was to re-name referred Coelophysis material as
Rioarribasaurus, and if no decision has yet been made, use of
Rioarribasaurus as a generic name in general discussion would seem to be
jumping the gun, to put it mildly!
If the obdurator foramen differences are real and Rioarribasaurus and
Coelophysis are different, then the usage of Rioarribasaurus is different
from that of the original proposal. In this case, if the initial objection
to the use of Coelophysis for other than the non-diagnostic type material
was valid, that situation still maintains and we need yet another name for
the referred "Coelophysis-but-not-Rioarribasaurus" material (and Coelophysis
is a nomen dubium).
The question of usage of Rioarribasaurus ahead of other Coelophysis synonyms
(? Longicollis ? - don't have the reference handy) also needs to be addressed.
I presume that this whole thing came up because of a rule somewhere that
says a type specimen can not be re-named? Given the enormous amount of
Coelophysis material, the simplest solution otherwise would surely have been
to re-name the undiagnostic type and keep Coelophysis for the rest??!
If anyone can provide the definitive explanation for all this (if there is
one), I for one would be extremely grateful.