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Re: PHYTOLITHS



A short while ago, I asked if anyone had ever looked for, or seen, phytoliths
on dinosaur teeth. Jerry Harris replied to my post privately and, with his
permission, I'm fwding it here..

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>PHYTOLITHS ON DINOSAUR TEETH?

>I would suggest diplodocids as test subjects. Whether they ate conifer
>needles or terrestrial ferns remains a matter of opinion. Anthony
>Fiorillo has previously looked at tooth microwear to determine
>sauropod diet, and found that _Diplodocus_ had little wear compared to
>camarasaurs and brachiosaurs. This might mean that _Diplodocus_ ate
>high up, well away from abrasive grit found at ground level, or it may
>mean that it ate soft terrestrial foliage that grew perhaps only a
>metre or two above the ground. Theoretically, phytolith analysis could
>remove doubt.
 
        Or, alternatively, it ate a high percentage of
non-phytolith-bearing plant material.  I don't think ferns produce
phytoliths, but I'm no paleobotanist, either.  The gymnosperms of that era
have broad, flat leaves atypical of modern pine/fir/spruce "needles," and
I'm not sure if there's been any analysis of the phytolithic content of
these leaves to determine any such thing.  I wonder if its possible to say
that any tooth wear in sauropods (being gastrolith-bearers) came more from
scraping them against branches to rake leaves off than from the leaves
themselves.  And, of course, how much of the wear came from manipulating
gastroliths in the mouth (either in ingestion or regurgitation)?
 
>I see problems in the idea, as mentioned above, but on learning of the
>implications of phytolith discovery, I wondered if it might be a subject worth
>nominating for investigation. If we simply don't know enough about Mesozoic
>botany and/or phytolith identification for there to be any success, then it's
>back to the drawing board. Likewise if archosaur teeth are simply useless at
>retaining phytoliths. But it's an idea...

        I like it.  I know the Morrison is poor for plant fossils from all
but a couple of locations, but surely there are other Late Jurassic floras
from other formations that might produce leaves whole enough and in enough
of an abundance for such an analysis.  As a corollary, I think I recall
Karen Chin having worked on a few possible coprolites from the Morrison
(and the overlying Cedar Mountain Fm.); herbivore coprolites may also
preserve leaf pieces well enough in thin section to ascertain phytolith
content.

Jerry D. Harris                       (214) 768-2750
Dept. of Geological Sciences          FAX:  (214) 768-2701
Southern Methodist University         jdharris@post.smu.edu
Box 750395                            (CompuServe:  73132,3372)
Dallas  TX  75275-0395

"Tyrannosaurs, though rarely seen, are certainly still around.
And no one knows just where or when the next one will be found."

                                  -- Calvin (aka Bill Watterson)
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"These aren't the droids you're looking for"
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