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RE: Dinosaurs with Guts



My name is Randy Irmis, and Im a geology student at Northern Arizona
University.  I've been lurking for a while, but this paper made me want to
comment:

I think, that Varricchio et. al. have provide very circumstantial evidence
that the hadrosaur remains found are indeed the gut contents of a
tyrannosaurid.  The most obvious problem with their diagnosis is that none
of the remains found are articulated.  The hadrosaur remains are only found
in association with the tyrannosaurid, and only one bone is in direct
association with elements of the ribcage.

My second problem is, why would a predator ingest the skeletal elements that
are found?  The area of the skull that contains the dentary has almost no
meat.  If any part of the cranium were to be disturbed by the predator, I
would expect it to be near the braincase, where there are nutritious soft
tissues (namely, the brain).  Furthermore, the vertebral column in a newly
killed animal would be hard for a predator even as large as a tyrannosaur to
disassociate.  This is especially true with the caudal vertebra in a
hadrosaur, where tendons effectively immobilize the tail.

The final argument given in favor of the hadrosaur being gut contents is
that the caudals found are acidically etched.  This certainly is a
compelling argument.  There are however occurrences of bone beds deposited
in acidic environments.  Especially notable is the Maiasaur bone bed in the
Willow Creek Anticline, where major parts of bone have been dissolved by the
acidic depositional environment.

I remain unconvinced this is truly evidence of a tyrannosaurid's gut
contents.  For a
a quality paper on true gut contents of a dinosaur, check out:

Molnar, R.E. 2000 "Gut contents of a small ankylosaur." Journal of
Vertebrate Paleontology 20(1):194-196

Perhaps Dr. Holtz will set me straight?

Regards,
Randy Irmis

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Jaime A. Headden
Sent: Wednesday, March 28, 2001 8:30 PM
To: dinosaur@usc.edu
Subject: Dinosaurs with Guts


In the _Journal of Paleontology_, we get a new "Gut Contents of"
to suggest the diet of one animal, at least, and paleoecological
implications thereof:

  Varricchio, D.J., 2001. Gut contents from a Cretaceous
tyrannosaurid: Implications for theropod dinosaur digestive
tracts. _Journal of Paleontology_ 75 (2): 401?406.

  The abstract and fulltext is available, as is the PDF, online
at
<http://www.bioone.org/bioone/?request=get-toc&issn=0022-3360&volume=075&iss
ue=02>

  *Daspletosaurus* preying on *Maiasaura*....


=====
Jaime A. Headden