Re: Words from an expert

[Casey <tuckercj@muohio.edu>]

References from Science Citation Index:

Body mass, bone ''strength indicator'', and cursorial potential of
Tyrannosaurus rex
                                                Farlow JO, Smith MB,
Robinson JM
                                        JOURNAL OF VERTEBRATE
PALEONTOLOGY
                                                    15: (4) 713-725 DEC
1995

Abstract:
We describe a new life restoration of Tyrannosaurus rex, based on a
fairly complete skeleton (Museum of the Rockies [MOR] 555). From the
volume of this
model, we estimate the live mass of the full-sized dinosaur as
approximately 6,000 kg. Because MOR 555 is a representative of the
gracile morph of T. rex, the
mass of the robust morph may have been substantially greater. The
''indicator of athletic ability'' or ''strength indicator'' of MOR 555
is 7.5-9.0 meter(2)/giganewton,
similar to previously reported results. The implication is that the
cursorial potential of Tyrannosaurus was limited, a conclusion
consistent with observed declines in
sprint speed with increasing body mass in living animals, and also
consistent with the tibia/femur length ratio, and the construction of
the hip joint, of the dinosaur.
Furthermore, mathematical models of the impact forces and decelerations
that would affect a Tyrannosaurus, were it to fall while running at a
high speed (20
meters/second), suggest that the animal would be killed in such an
accident. We speculate that the top speed of adult individuals of this
dinosaur species was about
10 meters/second.
--------------------------------------------------------------------------------------

Alexander RM.  1996. Biomechanics - Tyrannosaurus on the run
NATURE  379: (6561) 121-121
(no abstract available)
---------------------------------------------------------------------------------------

ALEXANDER RM. 1991. HOW DINOSAURS RAN
SCIENTIFIC AMERICAN  264: (4) 130-136

Abstract:
If all you had to go by were footprints in mud and a few bones, you
might conclude that humans do not run. Similarly, it is unclear whether
dinosaurs plodded or
galloped or pranced. With some physical principles from naval
architecture and mechanical engineering, the author calculates that he
could outrun Tyrannosaurus.
-----------------------------------------------------------------------------------------

Hope these help,

Casey Tucker
Dept. of Zoology
Miami University
Oxford, Ohio

********************************************************************

Richard Ellis wrote:

>
>
> Curiously, in the latest Scientific American (the one with the T.rexes
> on the cover), there are words from an expert on this very subject;
> the anality of such a gigantic creature to stop or even change course
> easily. George Gaylord Simpson wrote a little story called "The
> Dechronization of Sam Magruder," which was published posthumously in
> 1996. Sam Magruder, having found himself back in time some 80 mya, has
> to contend with marauding dinosaurs, including T. rex. Simpson
> (writing as Magruder) wrote, "Only as it loomed directly over me, its
> whistling resounding in my ears like the trumpet of doom. did I
> recover volition enough to leap to one side. Unable to throw so much
> momentum into a swerve, the tyrannosaur lumbered by, knocking down the
> small trees as if they were herbs, and finally skidding to a stop
> twenty yards beyond me."
>
> On 9/1, Daniel Saravia wrote:
>
> I have 2 questions:
>
> 1) How does he stop?
> 2) what if he falls while running at 45-50 Km/h (31miles/h)?
>
> Given the mass of a T-rex (6.4 metric tons per "Dinosaur Data Book" by
> David
> Lambert and the Diagram Group), the 50 Km/h speed + the acceleration
> due to
> gravity -- a fall while running would seem to be a very dangerous
> thing
> indeed.  Something akin to a fully loaded bus hitting a thick brick
> wall.
>
> Stopping or turning this much mass at that kind of speed would be a
> daunting
> task also.  Just some thoughts from a non-expert.
>
> Richard Swigart