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Re: New ref



>From what I understand, the Tyrrell did a study with placenticeras meeki
ammonites from Alberta to determine whether this was in fact the case, or
not.

Apparantly, they used actual nautilis in their study.  From what I have
heard through the grapevine, it was determined that some were mosasaur bite
marks, and others were limpett scars.

I have seen A LOT of "bitten" placenticeras, and quite often the shell
around the supposed bite mark is compressed inward, and sometimes it isn't.

It seems unbelieveable to me that, at least in the cases of Alberta
placenticeras, that limpets could be organised enough to attack an ammonite
on evenly spaced distances, on each side of the shell.

Unfortunately, I have never seen n Alberta placenticeras with a broken
mosasaur tooth still imbedded inside it.  We have one now that may have
such a tooth, and is currently under study.

Michael Schmidt

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From: Ralph Chapman <Chapman.Ralph@NMNH.SI.EDU>
To: dinosaur@usc.edu
Subject: New ref
Date: Friday, October 16, 1998 2:40 PM

I just saw this reference and had to mention it on the list. It is:

Kase, T., P.A. Johnson, A. Seilacher & J.B. Boyce. 1998. Alleged
        mosasaur bit marks on Late Cretaceous ammonites are limpet
       (patellogastropod) home scars. Geology 26(10):947-950.

My initial reaction was to be stunned considering the specimens and
pictures of specimens I've seen of Placenticeras (UK, Pierre Shale) that
had to have been chomped. However, the paper includes Seilacher, one of the
World's brightest human beings, and tries to argue that the nature of the
markings and limpet fossils associated with some argues against what seemed
obvious. I suggest a reading and if some of you - maybe Neil Larson or
someone else with big collections - wishes to answer the paper - perhaps
with some morphometric support (hint, hint) - it would be a neat project to
really try and nail this down (or not). Could involve simulation work to
work out the possibilities of getting patterns randomly that mimic the
shape of mosasaur snouts so well, etc. A nice controlled and short study.
Would be tough to figure out how limpets orchestrate some of the shapes
that seem awfully mosasaurian to me. However, as I'm running through the
paper, it has a distinct Seilacherian component to it which means the
apparent folly of it may just turn out to be correct (Dolph has an amazing
batting average on odd stuff such as this) and, at the least, will take
some very strong data arguing against it. Of course, a mosasaur tooth in
shell would help immensely.

Anyway, I was just hoping to stir up trouble. My job as a paleontologist.

By the way, if you've never read any of Seilacher's work, please do. The
man has done some incredible stuff - although being Dolphed, as someone at
Dinofest found out after giving a talk, can be a very uncomfortable
experience. He tends to ask questions that go to the center of a research
project and test the base of the researcher. Is a neat guy to talk with.

Trouble done,

Ralph chapman
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