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

["Stewart, Dwight" <Dwight.Stewart@VLSI.com>]

        -----Original Message-----
        From:   Thomas R. Holtz, Jr. [SMTP:th81@umail.umd.edu]
        Sent:   Tuesday, March 02, 1999 8:00 AM
        To:     Patrick Norton
        Cc:     dinosaur@usc.edu
        Subject:        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.
        >

        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

        @@@@@@@@@@@@@@@@@@@@@@@

           Tom is right on about the physics involved here.  Even "logic"
must bow to basic
        physics, as somebody or other once said. :-)  Bone can only be just
so strong & there
        can only be just so much muscle protecting it.  The big problem with
a really massive
        animal rolling over you (even if you are a 6.5 ton Tyrannosaurus
rex) is F = ma.
        And, that's just the ballistic component.  Stress induced by
sustained force would
        raise the internal pressure on bones & internal organs dramatically.
            Also, I would think a Tyrannosaurus rex would try vigorously to
avoid being off
        of its feet.  Dr. Holtz & others would have a better take on this
than I, BUT - how easy
        would it be for a T. rex to REGAIN it's feet from a prone position?
Especially in
        a fight?  T. rex doesn't look like it was built to quickly vault to
a standing position,
        unless he could get those powerful legs under him.  
           Also, the point about the height advantage is worth considering
too.  Why give that up?
        With the exception of sauropods, T. rex was taller than almost all
potential prey animals.
           I don't doubt that a Triceratops COULD knock a Tyrannosaur off
its feet under certain
        circumstances.  I just feel that such an event might shift the
advantage more in the
        Triceratops's favor.  

        Dwight