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Rough & tumble world (was Re: "Dinos of a Feather" )



At 07:59 PM 3/1/99 -0500, you wrote:
>Dr. Tom wrote:
>
>>Grappling with the jaws, sure; tearing and yanking with the powerful neck,
>sure; but rolling around with a 4 tonne _Edmontosaurus_ or 6 tonne
>_Triceratops_ or whatever is a good route for getting your rib
>>cage/skull/limbs crushed.
>
>
>But isn't that what the fossil record shows?--at least to some extent?  As
>Darren Tanke has pointed out recently, trackways show evidence of deformed
>toes and even limping dinosaurs (theropods and sauropods).   He also says
>that Hadrosaurs show a lot of evidence for bone trauma, including very
>serious jaw fractures, massive pelvic fractures and crush fractures to the
>end of the tail,  Tyrannosaurs are known to have suffered fractures,
>including fibula fractures, broken ribs and gastralia  (according to Darren;
>due to high impact falls).  Some of the more recent tyrannosaur skeletons
>appear to indicate even more rough and tumble lifestyles.....witness Sue and
>Stan and the like...
>
>Can we really rule out Tyrannosaurs ("the body") ventura?

Rough and tumble, yes; lots of damage, yes.  But we were talking explicitly
about rolling over on its back during routine predation.  Rolling around
while wrestling a big hadrosaur or _Triceratops_ wouldn't merely result in
broken bones: this would very likely result in *crushed* bones (notice how I
used that particular word in the quote above), and ribcages (and burst
internal organs), etc.  Heck, I would expect this is the one time you really
WOULD get a hepatic piston in a tyrannosaur, as liver gets squashed forward
into the lungs...

Unlike stop-motion animation movies, you can't just scale up the behavior of
small animals and say that large animals did exactly the same thing.  Some
allowances have to be made to the laws of physics and the mechanical
strengths of flesh and bone.

So, sure: body blows, tail slams, kicks and so forth (although even a half
nelson would be outside of a tyrannosaur's or opponent's ability...) are
expected, and a significant amount of breakage did occur.  However, thinking
that a _Tyrannosaurus_ vs. _Anatotitan_ predation event was just a scaled-up
version of mongoose vs. cobra seems very unlikley.

And that's where this thread began: with the question about what would
happen to alledged _T. rex_ feathers when it rolled on its back to wrestle
with its prey.

(And, come to think of it, rolling on its back would probably be the worst
possible move a tyrannosaur could do: it loses its height advantage (death
from above) and its speed advantage, and puts itself in a position
(literally!) where the potential prey item could use its entire weight
against it.).

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