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Moving at the Speed of Rex [was Re: documentarian...]



Steve Hullfish wrote:

<...the reports claimed that because of the fossil
evidence from Sue, scientists have determined that
instead of previous theories that put T-Rex's top
speed at something like 35 miles and hour, it could
probably only do 15 mph. I am interested in how the
first theory was developed and why a single T-Rex
skeleton would change the theory for the whole
species?>

  Going all the way back to Osborn and the famous
paintings of Knight at the AMNH, it was originally
hypothesized (them being giant lizards) that dinosaurs
had the general metabolism of reptiles (i.e., the
"cold-blooded," tachymetabolic things that they
were... :) ), and could not lift they tails off the
ground (unless they were too short, they _had_ to
touch the ground, and I personally find every
restoration Knight did I've seen of *Triceratops*
laudable in its unoriginality because of this). Even
Ruben et al. suppose these lumbing titans could
acheive momentary (turbo-charged) energetic moments;
but, sadly, they were not to last. They went the way
of the dinosaurs ... oops.... :)

<What kind of a team of scientists had to be gathered
to make perfect this theory?>

  Absolutely none -- no perfection is assumed in
science, truth is an object, a goal, not a assumed
occurence, so we suggest likelyhoods and
possibilities. Take quantum physics, a science
attempting to unravel the mystery of the universe, and
it starts out by showing how an experiment shows a
previous hypothesis was incorrect, and continues to
demonstrate the experiment. Fin.

<You have some guess I suppose as to how long a stride
that the beast could make, but then how do you figure
how quickly that stride can be accomplished by looking
at bones?>

  The energetics of dinosaurs (and the whole subject
revolves around that) has fluctuated, but Alexander in
several papers and a book has worked on the
biomechanics of limbs in dinosaurs, followed by
ecological studies by Farlow, and Bakker, in the 70's
and 80's, a recent one by Farlow et al. in the 90's on
how to trip a rex (in _JVP_), and further work by
Gatesy and others in the 90's on the limbs of
theropods compared to birds, then Holtz in 1994 on the
ability of coelurosaurs to be high-grade cursors;
similarly, Gatesy and Middleton (1997) have computed
the limbs of theropods into a ternary diagram to
achieve similar results, and showed that, at least,
rexes weren't sluggish monsters.

  Basically, rex has limbs with a long tibia and
metatarsus, unlike more sluggish animals (and I'm
being unfair, as crocs have relatively long tibiae,
they can outrun humans in the short run), that gave
them a leverage proportionately greater than ours, and
so may have sped forward about 35mph, as the estimates
went, using hip-to-ground figures in pace/stride
calcs, and using Alexander's formula to calculate
speed from stride. Recently, though, complete limb,
dorsal, pelvic, and caudal material in _one_ specimen
(not until Sue) has full leverage been able to be
taken into account. The results suggest (I'll not trod
on Brochu's feet here, his croc might bite me) a much
lower top speed, but still atypically faster than us
on the average.

<I'm guessing the strength/depth of the ligament
attachments to the bone give an indication of the
power of the muscle attached to it, but what do I
know?>

 Jaques Cuvier pioneered the study of morphology and
translation of known material to fossil material
(comparative morphology) that is our best guide to how
we think a muscle was shaped in an animal we ould not
dissect for this purpose. Certain qualities of anatomy
are assumed to be true, and landmark sites for
ligaments and muscles in birds and crocs are used to
suggest the placement of the mm. gastrocnemius (flexes
lower leg), iliotibialis (pulls legs sideways),
caudofemoralis (pulls femur back), pif/i,e
(puboischiofemoralis internus and externus, pulling
femur in, forward, or back, as in birds), etc.

<How do you guess how long it can keep up this pace?>

  General energetics (how fast it could keep this up)
are sustenance problems I think could not be asserted
on the known evidence, though one can use modern
studies to reflect on fossil studies (Horner and
deRiqles have been doing something like this for a
couple years with bone-slicing in *Hypacrosaurus* and
*Orodromeus* -- the growth curve of the former is
closer to an ostrich than a crocodile) but this tells
us only a little about energetics and such.

<How accurate would these theories be if they were
applied to human bones? What speed would a
paleontologist come up with if they looked at the
bones from MY legs?>

  Human anatomy is given as a guide to knowing the
placement of fossil limbs and musculature, but a
better guide is the crocodile or bird, where the limbs
are in similar proportion, morphology, and location,
than to humans, who have many novel features for being
vertical bipeds, including lacking a whole lot of
femoral leverage in the pelvis (one of the reasons
we're so slow).

<How do you guess on all these dinosaur behaviors from
bones? I suppose there is fossil evidence beyond just
the bones. How do figure whether T-Rex hunted or ate
carrion? I don't care about the theories themselves
really, but how they came to be.>

  Based on considered equal lengths in the femur and
tibia of rex, Horner suggested that speed was not
rex's thing (Currie and Holtz disagree), and as such,
could not chase down its prey. There is some argument
over whether Horner himself is playing devil's
advocate, or he really advocates this, but that is
outside the discussion. Numerous lines of evidence
suggest rex was a detritivore (carrion-feeder): the
optic lobes are so incredibly immense relative to the
rest of the brain, even, and Horner suggested that a
relative detritivore (the turkey vulture) was
comparable in this regard for detecting rotting meat
at considerable distance -- rotting meat smells worse
(and more) than live flesh, contained in its skin with
associated disquising odors; the limbs were short, and
thus running down a trike was out of the question, and
impetus and inertia would force rex into a spasm of
death-throws if it fell at faster than some 11mph, so
it _couldn't_ run too fast, and Horner was quick to
point this out; the jaws of rex are built like those
of the hyena, with giant palate and (frankly) bananas
for teeth, built as Erikson has pointed out, for
crushing, so a crushing, bone-eating habit is known
only in habitual detritivores, and Horner, Erikson et
al., and Holtz have remarked on this.

  Similarly, lines of evidence suggesting rexes were
carnivores follow similar lines: Stevens (1996) has
demonstrated that the eyes of rex were the size of
tennis balls, perfectly large enough, with big enough
optic lobes to have a great amount of acuity,
something you don't see very much in a detritivore,
though caniform and dog-like animals typically rely on
their noses, not eyes, and being a bird of prey, the
vulture with have good eyesight plesiomorphically
(right?); Rex has a real short tail, tibial leverage
was greater than femoral leverage (Holtz, 1994), and
the whole forequarter region was reduced to emphasize
the head, light as a feather, for balance -- running
was in this animal's ancestry, at least; there are a
few fossil skeletons showing healed wounds that could
only have been acheived by a rex, including the mount
of the edmontosaur at the DMNH that looks about ready
to turn on the diplodocid on its rear, and these were
(I'm sorry, forgot the reference) suggested as
evidence of predatory, hunting behavior, not "Oops,
I'm sorry; I though you were a corpse -- please, prey,
continue with your merry life, and don't forget to
break a leg! I'll be there at your side any time you
should call!!!".

  When Brochu publishes his monograph on Sue, we can
hope that some questions will be settled, the log from
inside her head can be mounted, and more scientists
can begin to work on specialist studies involving
histologies, musculature, dynamics and energetics,
neural morphology, systematics, biomechanics, ecology,
paleopathology, etc.

  My ... ahem ... $.02. :)

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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