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RE: Many, many thoughts & responses re: the Hutchinson-Garcia paper - LONG

Just adding my 2.5 cents to the roar:

First, I would love to be able to say that _T. rex_ ran at 35-40 MPH.
HOWEVER, we have NO EVIDENCE that currently CONTRADICTS John & Mariano's new

Second, their web site is very well done.  [I do not have the paper, and can
only go by the web site, the articles, and comments on the list here.  The
physics seems sound. (BTW, I have a B.S. in Physics)].  Overall, a job well

Third, a 5 m/s to 11 m/s range of speed translates into 10 to 25 mph range.
This actually quite fast for a large animal, especially one balanced on 2
legs.  Remember that the fastest time for a human is just over 10 m/s - and
that's only for 100 meters!  As mentioned, even some of best conditioned
members of this list might have great difficulty passing 8 m/s (around 18
MPH).  [Note that I, personally, do not qualify as still being
well-conditioned.  :-) ].  So most of us would be _T. rex_ chow!

If we look at how large the femur and illia are in the _T. rex_, we
naturally expect that it could  move a massive creature very rapidly.  But
there are limits.

Consider this, however:  Of all the large theropods (_Carcharodontosaurus_,
_Giganotosaurus_, _Allosaurus_, etc.) _T. rex_ seems to be the one with the
MOST massive thighs and hips.  This would imply, at least as far as I can
see, that _T. rex_ could move faster than those others, because their legs
and hip structure would not allow for nearly the same amount of muscle mass
(or percentage of those muscles versus total body mass).  True, on an
absolute flat-out race between the 3 dinos I mentioned above and _T. rex_,
_Allosaurus_ MIGHT win because of the lower overall body mass.  _T. rex_
would come in second.   I would be interested to see if John would analyze
_Allosaurus_'s speed range as well, to see if my surmise is correct.

Concerning some of Dann's points below:

The 9.1 m/s mentioned in Tom's post and Dann's are under the maximum
proposed by the Hutchinson-Garcia paper.  It remains possible that this is
indeed the top-end for the safest, fastest speed by a _T. rex_, and possibly
for the Jurassic theropod as well. (This is just over 20 MPH for us
Americans :-).

As to whether _T. rex_ was an ambush predator, I think that an ambush would
be a very good use of those massive legs, surprising the unwary
_Edmontosaurus_ (etc.).  However, I think we need John to work on the model
for 4 legged animals, and crank some of the larger sauropods through it, and
present us with a speed comparison chart (Or, maybe some enterprising grad
student could finally find a topic in this for his/her dissertation).

Another use of _T. rex_'s massive legs could be to hold down his prey, much
like modern birds of prey do.  Jack Horner, in one of his many statements
about the poor hunting skills of _T. rex_, said "Maybe he hid behind a rock
and jumped out and kicked over a _Triceratops_!".  Ha-Ha, Jack - maybe
that's exactly what he (_T. rex_) did do!  Then, he held the animal down
(with those legs), and bit into its back and neck to kill it.

I've also thought that maybe the huge legs on _T. rex_ would make it much
easier for the animal to raise itself up from a "prone" position to stand.
(I put quotes around prone, because I think the animal couldn't lie down
completely - probably rested on the pubis, which I think would have been
very padded).

I like Currie's idea about the younger rexes doing the hunting.  Of course,
it is possible that the younger ones did the chasing, and chased the prey to
the waiting adult, who provided the coup-de-grace.

Referring to the recently concluded Olympic games, the current state of the
art in figure skating is a quadruple spin (Quad Toe-Loop and Quad Lutz).  It
may come to pass in our lifetimes that someone, somewhere will be able to
leap from skates, spin 6 times, and land, safely and elegantly.  {Note that
NBA players like Kobe Bryant could probably jump high enough to spin 6 times
and land safely - but I doubt they could do it on skates - let alone
elegantly).  I'm sure that someone will be able to calculate an upper limit
to how high someone can jump from ice, and how many times they can spin
(which is a function of how high they jumped), and still land relatively
safely.  This is a similar situation with _T. rex_ - there has to be some
sort of limit - These are real, physical creatures, and they are bound by
the same laws of physics we are.

Just remember, although _T. rex_ is not a speed demon, it's still a very
fast animal.  And it still is one of the most powerful of the theropods.

Thanks for listening! :-)

Allan Edels

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Dann Pigdon
Sent: Friday, March 01, 2002 6:46 PM
To: dinosaur@usc.edu
Subject: Re: Many, many thoughts & responses re: the Hutchinson-Garcia

"Thomas R. Holtz, Jr." wrote:

> Let's keep things in perspective: 5 m/s is still fast for a big animal,
> that is BELOW the walk/run transition.  Incidentally (for thought
> experiment's sake), if a _T. rex_ of MOR 555's size could move at Fr = 3.8
> (the dimensionless "speed" of Day et al.'s Middle Jurassic tracksite),
> would be 9.1 m/s.

So: Farlow, Robinson and Smith calculate that a safe speed for a T.rex
to avoid tripping would be around 35 KPH. These M.Jurassic prints also
seem to indicate a similar speed for a large theropod (9.1 m/s = 32.7
KPH). Suggestive, non?

> According to their model, _T. rex_ was not a fast *runner*.  This doesn't
> mean it was slow!  If MOR was doing 5 m/s, it could still probably catch
> most of the people on this list if it were chasing us!

Indeed. Elephants don't "run", but they can get up one hell of a speed.
Plus they are also susceptible to fatal tripping, yet that doesn't slow
them down much.

Lions and leopards are much slower than many of their prey. In fact,
ambush predators in general seem to be fairly robust creatures - not
unlike a certain large theropod? If you're not chasing down gazelles for
a living, why be an olympic sprinter?


Dann Pigdon                   Australian Dinosaurs:
GIS Archaeologist           http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/