Re: Coelophysis/Rioarribasaurus

["Nicholas J. Pharris" <pharrinj@PLU.edu>]

On Sun, 21 Apr 1996, Graeme Worth wrote:

> 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.

Not all other material.  _Rioarribasaurus_ is for the Ghost Ranch, NM,
animals.  _Coelophysis_ itself is, as I recall, from the Northeast.
Other scraps that have been referred to _Coelophysis_, like _Longosaurus
longicollis_ or _Podokesaurus holyokensis_, were not subsumed under
_Rioarribasaurus_.


> 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 don't know why the Arizona animals were referred to _Syntarsus_.  _S.
kayentakatae_, the American species, is more heavily built and has head
crests, which the African species, _S. rhodesiensis_, lacks.  But I
digress...


> 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!

Not if you believe the Ghost Ranch specimens to be generically distinct
from _Coelophysis_!


> The question of usage of Rioarribasaurus ahead of other Coelophysis synonyms
> (? Longicollis ? - don't have the reference handy) also needs to be addressed.

_Longosaurus longicollis_ is also based on material of dubious value, as,
to my knowledge, are all other genera that have been subsumed under
_Coelophysis_.


> I presume that this whole thing came up because of a rule somewhere that
> says a type specimen can not be re-named?

Indeed.

> 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??!

That would have been tidy, but, as you mentioned, the original specimen
described as _Coelophysis_ carries that name with it no matter what may
happen.


> If anyone can provide the definitive explanation for all this (if there is
> one), I for one would be extremely grateful.
> Graeme Worth

I hope this has helped!


Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8206
PharriNJ@PLU.edu