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Re: Paul Willis' 2/7/98 2:04 AM posting Re. Re. Re. Deinosuchus, etc.



At 07:26 AM 2/7/98 EST, Mary Kirkaldy wrote:

[Ray Stanford's comments deleted]
>
>The above posting and previous are specific examples of why it is 
>absolutely imperative for new list members to read the Dinosaur List 
>guidelines and archives for a while before posting.

Seconded!

>As this is a list for the scientific discussion of dinosaurs, speculation
>is best couched in the form of a question.  Also, as GSP said last
>year, "If you are going to play with the big boys..."  
>
>I am sure that Dr. Willis'  fossil crocodile publications, books, radio 
>and television appearances are sufficient qualifications to speak as an
>expert on this list.

Quite so!  Although I might have phrased things differently than Paul
(although possibly not), his concerns were valid and I concur with him on
the intent.  We should be EXTRAORDINARILY careful when assigning fragments,
ichnotaxa, etc. to established skeletally based genera and species.
Otherwise, folks like Paul and I spend a lot of time playing mop-up when
others start citing (in this case) massive jumps in the stratigraphic and
geographic range of taxa.

A similar problem exists for some of the isolated Chinese tyrannosaur teeth,
placed in the genus Tyrannosaurus even if there is NO evidence for such a
placement.  People who catalog lists of occurences may not recognize that
there is no support for such a placement, and record this as an observed
occurence of that genus tens of millions of years earlier than demonstrable
specimens.  Still others will take the catalog, put it up on the web in a
computer file, and soon commercial companies are copying it and putting it
in their kids books.  Ugh.

(Or the extreme example: refering simple blade-like theropod (or even
non-theropod teeth) to "Megalosaurus", giving this taxon a global geographic
range and a trans-Mesozoic stratigraphic range! Not bad for a form limited
on skeletal data to part of the Middle Jurassic of England and (probably)
Normandy).

A big crocodyliform track is just that.  There is no reason to refer it to a
particular, skeletal-based taxon (like Deinosuchus) if it is way outside the
range (stratigraphic or geographic) of the known specimens of that taxon.
There are other big Cretaceous crocodyliforms, perhaps not as famous, but
which were potential makers.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661