Re: cf. Giraffatitan tracks reported

["Jaime A. Headden" <qilongia@yahoo.com>]

I wrote:

<<The amount of pressure exerted by the foot is not the same as the value
of the mass of an animal or its weight. For instance, a landing from a
jump produces several hundreds of pounds of pressure per square inch in a
145lb human such as myself, and this increased with height of the leap.>>

and David Marjanovic (david.marjanovic@gmx.at) wrote:

<Sure, sure. But I'm pretty certain sauropods didn't jump, at least this
one didn't, and the differences seem a bit big to me for normal walking.>

  The point I was trying to make was that if you took a 10 tonne animal
and a sandbox of Olympic proportions and provided exact criteria for the
substrate density, water content, and consistency, and then take your 10
tonne animal and have it walk, then run, across the surface, or air-lift
it down and have it stand still, you will get three different depths of
each imprint.

  The measure of the force of a step, when walking or running, value with
the mass and the inertia of an animal, and the substrater displaces
relative to it's consistency, density, water content, angle of force from
the foot, and the weight and inertia of the animal. Each of these must be
calculated for a given track to measure the 1) speed 2) weight, and 3)
environment in which the track was produced.

  Thus, a 10 tonne animal walking and a lighter, ~7 tonne animal running
may produce similar displacement and depth of track. Saying the
displacement and depth relate to mass only is therefore not the whole
truth, but not seeing the added complexity of the issue. Style of contact
is important to gague. One can use Alexander's method to figure out the
hip height, but then one must use more complex math, including math worked
on by Hutchinson and Garcia, to figure out how the track was produced.
Both Swisher and Farlow have been working on track formation and effect of
locomotion in variable substrates, so this is hardly being ignored right
now.

  That was all, and appologies for lack of clarity before.

  --

  Meanwhile, it would benefit a lot of people to think of things in terms
of Zen, but that's my personal, non-scientific viewpoint.

  Onto birds...

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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