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Re: T. Rex the hunter (the DMNH Edmontosaurus revisited)



Dann Pigdon  wrote:

> One thing that I have noticed amongst many extant scavengers is that
> they usually have long narrow snouts/beaks to probe deep into
> a carcass (vultures, maribu storks, jackals). I can't see a Tyrannosaur
> using that great box of a head to pick a carcass clean.

With the bite power (thousands of lbs/square inch) and massive teeth of
T. rex, I doubt
it was a carcass-picker. It probably was a carcass-amputator.

After someone on this list mentioned the photo of a healed-over backbone
injury on the Edmontosaurus at the Denver Museum of of Natural History
(featured in Johnson and Stucky's book _Prehistoric Journey_, 1995, page
89),
I had to do some checking.  The photo is large enough so that some
very crude generalizations can be made.
The first thing that struck me about the mounted specimen (DMNH 1495)
was how
undamaged the rest of the vertebral column was.  The damage occured
only on caudal vertebra #15, and only the top half of the neural spine
was missing.  It also appears that some ossified tendons below
caudal#15 were also damaged.  The 15th caudal vertebra is situated
in the front half of the tail.

The second thing that I wondered, as I did a flash-back to remembering
the width
of the premaxillary region of T. rex, was: how could a T. rex nip off
the top of the neural spine of only one vertebra, while leaving the
adjacent neural spines undamaged?  The premaxillary teeth ("nipping
teeth")
on T. rex occupy a portion of the skull that is about 2 to 2 1/2+ feet
wide.
The anteroposterior length of a single neural spine on Edmontosaurus is
much less
than 2 1/2+ feet.  So, unless there are healed-over injuries on the
adjacent
vertebrae that cannot be seen in the photo, I am having a hard time
accepting that the specimen is a clear example of a failed predation
attempt.

The intrinsic problem here is that a predation bite that can
unequivocally be attributed
to T. rex would, because it would be an inherently large wound, probably
kill the 
prey in the process.

Perhaps this neural spine was snapped-off after having been stepped on
while the
animal was laying on the ground (sleeping, egg-laying, etc)?  The tip of
the
neural spine would still remain (essentially, floating) in the animal's
tissue, while
the base of the spine heals.  The tip could also have been resorbed
after it was broken off.
Greg Erickson is familiar with this particular specimen,
but since Greg isn't on this mailing list, perhaps someone else who has
seen the specimen up-close could add to, or correct my impressions?
Just some random paleoecological musings.
                         <pb>