Re: _Nanosaurus_ extract

[jdharris@lust.isem.smu.edu (Jerry D. Harris)]

At 2:22 AM 8/18/95, P2158753@vmsuser.acsu.unsw.EDU.AU wrote:
>        A second controversy surrounding _Hallops_ relates to
>its stratigraphic provenance and age.  The specimen was found
>in an allochthonous float block and displays preservation
>characteristics atypical for the Morrison Formation from which
>Marsh originally thought it to be derived.  Based on
>sedimentological evidence it now seems likely that the source of
>the _Hallops_ slab is the Ralston Creek Formation which
>occurs below the Morrison Formation and is Middle Jurassic
>(Callovian) in age.

Steve et al -

        Since you are otherwise so well informed on the subject, I'm very
surprised to see that you aren't aware of the latest work on _Hallopus_ and
its stratigraphic position!  See

Ague, J.J., Carpenter, K., and Ostrom, J.H. (1995).  "Solution to the
_Hallopus_ Enigma?"
        _American Journal of Science_ 295:  1-17.

in which petrologic analysis definitively demonstrates that the original
_Hallopus_ block is from a sandstone ledge at the "Cope's Nipple" quarry,
very high up in the Brushy Basin-equivalent of the Morrison.  This croc was
running around at the time of the largest sauropods and stegosaurs -- Jim
Kirkland has suggested that these cursorial crocs might have been egg
thieves.

        The Ralston Creek is a rather unfossiliferous formation; the fauna
known from it consists almost entirely of fish, as far as I know.



Jerry D. Harris
Schuler Museum of Paleontology
Southern Methodist University
Box 750395
Dallas  TX  75275-0395
jdharris@lust.isem.smu.edu
        (Compuserve:  73132,3372)

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