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T-rex. falls and sujectivity



Hello all,

Let me begin by giving Dr. James Farlowand his associates, Matt B. Smith
and John M. Robinson due credit for undertaking such a study as outlined in
the paper we are talking about. (Body mass, bone "strength indicator," and
cursorial potential of Tyrannosaurus rex, Journal of Vertebrate
Paleontology 15(4):713-725). Obviously much work and thought went into this
project. I now formally thank Dr. Farlow for caring enough to send this
non-pro a copy of this paper which allows me present my thoughts from a
slightly less ignorant position.

There are some points I wish to address, as follows;

1. Hard surface falls are not proven to speed deceleration, and the reverse
is likely. Motocycle crash comparisons are valid because the increased
speed decreases the "crush" effect stated in the paper. The validity of my
statement is supported by physics. The speed of racing motorcyclist,
sometimes in excess of 150MPH(200 Lbs. X 150MPH), more than offsets the
lowered hieght from which they fall. Potential energy is increased
geometricly with speed, however the contact force is spread over time and
distance. A bullet, fired from a exactly level rifle has the exact same
falling speed as one dropped by hand at a given height. The variable,
forward speed, has no effect on fall rate, until one reaches near escape
velocity. At that point what goes up does not have to come down. This is
why a stone skips when thrown across a water surface and sinks immediately
when dropped straight down. Hard surfaces are desirable when impacting at
speed.

2. The specimen studied specifically, MOR 555, is the gracile morph, and
strength indicators may not be accurate for the more robust morph.
Variables unaccounted for, or at least not mentioned, include bone strength
and body mass placement. By this I mean weight and size differences in neck
and tail structure. These difference could allow the robust form to react
and balance differently than the gracile form. The gracile form may have
also been quicker to react to the possiblity of a fall.

3. On page #722 the paper states, "We did not do a seperate calculation for
the head of the rhinoceros, because we had no basis for estimating its
mass". Either this is a misprint or there is something wrong. If an
estimation of mass cannot be made for an extant creature, how can one even
begin to estimate the mass of an extinct one?

4. Head size does not equal strength or weight. I would be willing to bet a
fair sum of American dollars that the head of a rhino is much heavier,
cubic inch for cubic inch, than the flexible and air-filled head of T-rex.
The flexibility factor alone precludes a comparison of the rhino and the
Tyrannosaurus rex. The skull of T-rex, with that flexibility built-in,
would seem to be a great impact absorption tool, whether from falls or from
hunting lunges.

5. Falling from a greater hieght, while adding to the impact forces, also
allows for corrections as time before the event is also increased. In the
event a T-rex. were to be aware of the imbalance prior to the "point of no
return" surely it would have enough reaction speed to alter its angle of
attack. Headlong plunges toward the dirt, without correction, doesn't fit
any predatory creature. I submit that bipedal predatory dinosaurs were
generally quicker than quadrapedal mamals, on the basis that the  dinosaurs
reptillian nature was instilled in evolutionary selection.  Elephants
herding and near freedom from predation, and rhinos too in the later, don't
require the same swiftness as needed by dinosaurs in either the young or
old.

6. No mention is made in the paper in regards to neck strength in T-rex.
and without this data the statement that the body would overtake the head
and break the neck is suspect. Would it not be possible for the T-rex. to
stiffen its neck, shift its head to the side, or take whatever means needed
to protect itself? What animal doesn't?

7. Without soft tissue data, and complete data at that, the overall mass of
any creature must be questioned. Estimations and geusswork lead to
guesstimations, and that leads to errors. Lung capacity, stomach and gut
size, and other soft tissues could varry wildly from what we think we know
now. These variables have to be considered before any assumptions are put
forward as fact.

I know I have placed a black cloud on the paper by these men, and after
having said all of this I could be entirely wrong. Logic, however, leads me
the believe that T-rex could not only run swiftly but  if it fell most
likely survive. Further study could prove me all wet, as wet as a carp.
Please do not take offense for this longwinded expression of doubt. When we
stop questioning each other our overall knowledge of the world we live in
will decline.

Roger A. Stephenson
rstephen@cswnet.com
Oh, by the way, GO HOGS!!!