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RE: New Tyrannosaurus paper




-----Original Message-----
From: Toby White [mailto:mwhite@houston.rr.com]
Sent: Wednesday, February 27, 2002 8:14 PM
To: dino.hunter@cox.net; 'Dinonet (E-mail)'
Subject: RE: New Tyrannosaurus paper

Tracy:

Hutchison has gone into the differences in locomotion between birds and
more basal theropods in huge detail in previous papers.  A few are cited
below.  I don't pretend to understand all of it, but its fairly safe to
assume that this is not a mistake he'd make. <<

Yea, I've got those papers lost in my room somewhere :(

>From the newspaper accounts, it also doesn't look like the detailed
mechanics have much to do with the result here. Its just a matter of the
energetics of moving a body of that size over the ground.  How the
pieces fit together won't have much effect on the muscle mass needed to
do the job.

>>That said, you may have a point about the ilia.  If (big if) I remember
Hutchison's papers well enough, that would mean a big caudofemoralis.
Having much of the muscle mass for the legs actually reside along the
hip and base of the tail might allow the dinosaur to cheat a bit on any
assumption that the leg muscles must be in the leg.

The cnemial crest may be more problematic.  I dunno exactly what the
crest was used for in non-avian dinosaurs, but one might suspect that it
is related to an ability to swing the lower leg through a wide arc
*without* moving the femur so much. That's the way it gets used in, for
example, loons.  Now a real bipedal sprinter might not need that
mechanism. Its got time in the air to move the tibia, and it's pumping
the femur up and down for all it's worth in order to get speed at the
expense of efficiency.  The more likely conclusion might be that the
tyrannosaur was either adapted for long-distance efficiency or to make
the most of stride length in a fast walk.<<


The problem is as I've pointed out and you also pointed it out in the above
post, the femur of theropods and birds are different in their orientation.
The femur of birds move more in the vertical plain while in theropods, and
dinosaurs as a hole, the femur moves more horizontal. This means in birds
the leg cycle of femur moves up and down and the lower leg does all the
major movements while in dinosaurs the femur moves for and aft and the whole
leg is used in the leg cycle. How can we compare these two radically
different leg movements and come to a conclusion that they are the same? I
can't see that. I know in some birds the femur comes close to vertical as
the 'down' stroke of the leg cycle, but in theropods the femur never even
gets close to vertical.


But, as you say, lets read the paper and find out. <<

Yep.

  --Toby White

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074