[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Tyrannosaurus rex was a fast runner



On Fri, Mar 08, 2002 at 10:32:11AM -0600, kyle robert brudvik sent:
> Be careful here, you are comparing obligate quadrupeds with obligate
> bipeds.  Especially in your bear example, the spinal column plays a large
> role in energy storage and transfer to the legs during running that it
> would not play in bipedally dinosaurs.

Certainly not in the same way, but it would be possible to use the
entire vertebral column as an oscillating spring storage mechanism; if
you look down on a running theropod, there's at least the possibility of
watching the head and tail bowing to the left and then the right as the
spine flexes to do energy transfer from leg to leg via long muscles
attaching between the axial and appendicular skeleton.

I really do need to get ahold of the whole paper, but as I understand
it, John Hutchinson's model treated the legs in a vertical plane, and
explicitly supposed that a running phase -- spring mass, rather than
inverted pendulum -- forces decoupling of the limbs in terms of energy
transfer, and I'm rather curious if that's necessarily the case or if
there might be horizontal bowing and energy storage via a tail-and-torso
system.

Something like:

Right foot thrusting; tail and torso swing *left*, simultaneously
pulling on (shortening) the caudiofermoralis of the right leg, and
lengthening the caudiofemoralis of the left leg as it swings forward.

Left foot touches down; the tail and torso are as flexed leftwards as
they're going to go.  Left leg starts its thrust phase.

As the left foot thrusts, the tail and torso start to swing right, and
the elastic return of tendons and ligaments goes into lengthening the
left caudiofemoralis during the later part of the thrust phase since
they'd mostly be unloading from the point of view of the left leg until
they got past the midline again.

I don't know if anyone has formally modeled such a mechanism?

-- 
graydon@dsl.ca   |  Hige sceal þe heardra, heorte þe cenre,
                 |  mod sceal þe mare þe ure maegen lytlað.
                 |   -- Beorhtwold, "The Battle of Maldon"