T. rex, the careful walker

[rowe@lepomis.psych.upenn.edu (Mickey Rowe)]

George Pesely's excerpt of the article from the Nov. 16, 1994, issue
of _Chronicle of Higher Education_ (written by Kim A. McDonald)
included this section:

> "'_T. rex_ didn't have much of a wheelbase,' says James O.  Farlow,
> a professor of geology at Indiana University-Purdue University at
> Fort Wayne and an expert on carnivorous dinosaurs.  'If _T. rex_
> fell while moving at speed, it would have been fatal.'

I was curious about what sort of speed Dr. Farlow was talking about
here so I contacted him.  With his permission, I'm posting the
following information which he sent to me:

:  I have a paper in press in JVP that addresses the issue of T. rex
: speed.  Matt Smith sculpted a life restoration model of Jack
: [Horner]'s Tyrannosaurus, which I used to estimate the body mass of
: the beast.  We then used a CT-scan of the femur, and measurements of
: the bone, to calculate [R. McNeil] Alexander's "strength indicator."
: Our result was almost exactly what Alexander got earlier, so the
: result seems rather robust.

[ When I contacted Dr. Farlow, I specifically asked if his speed
estimate was closer to Alexander's or Bakker's version.  As I recall
from Alexander's SciAm article of a few years back, his claim is that
due to Tyrannosaurus' relatively weak bones, the animal could only
move about 17 mph--around 8 m/s.]

:      I then recruited a local physicist, and he and I did some
: mathematical models of the impact kinetic energies and decelerations
: of the torso and the head of Tyrannosaurus, were it to fall.  The
: vertical component of impact force and deceleration is obviously
: unaffected by the animal's ground speed at the time it falls, but
: the horizontal component obviously is.  To make a long story short,
: we suspect that a Tyrannosaurus that fell while running at 20 m/s
: (close to Bakker's estimate) would have a very good chance of
: becoming the dinosaurian equivalent of creamed chipped beef.  Even
: if it were to fall while standing still, the impact force and
: deceleration affecting the head could be severe or even fatal.  We
: therefore question that the benefits of running at Bakkerian speeds
: (even if the critter could do this structurally, which our results
: for the strength indicator make us doubt) would outweight the
: associated risks.
:
:      This does not translate directly into an estimate of the
: animal's sprint speed.  However, we did some arm-waving comparisons
: with what modern elephants and white rhinos do, and said that we
: would not be surprised if Tyrannosaurus was capable of 10 m/s, and
: possibly even 15 m/s.
:
: Like I said, all this is in press in JVP, if you want the details.
:
:      Incidentally, I think I may be indirectly the source of a lot
: of Jack's interpretations about Tyrannosaurus biology.  I published
: a paper early this year in Historical Biology that argued that
: tyrannosaurs may have been very good scavengers because of the
: elevated positions of their eyes and noses.  I sent a
: pre-publication copy of this paper to Lessem and Horner when they
: were working on their book.  Similarly, Jack has a pre-publication
: ms of my JVP article.  Jack takes the argument farther than I would,
: though.  I think Tyrannosaurus was the carnivorous equivalent of the
: proverbial 500-pound gorilla, and ate anything it pleased.  If it
: found a carcass, party time, but if it encountered a prey animal it
: could attack at reasonably low risk to itself, I'd sure hate to have
: been said herbivore.

Given Dr. Holtz' analysis of lifestyles of the big and vicious, I
thought the above would be a good addition to the conversation.

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)