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Re: Running T. rex

David Marjanovic wrote:

<Well, "*lol*" is surely an exaggeration, but has anyone ever thought
that ornithomimosaurs couldn't run?>


  Perhaps I should start by saying not once has it been presumed that
ornithomimosaurs were incapable of running. That the hindlimbs of
tyrannosaurs and ornithomimosaurs are identical has been acknowledged
for several decades, but certainly Holtz (1994) was the first serious
assessment of this theory, and quantified it. Next, one must observe
the physics of the two animals in relation to one another: the largest 
ornithomimid is *Gallimimus*, and its hind limbs come up to about human
head height (rough estimate, the type still had some growing to do).
What with all the mass per second involved in moving, it's pretty close
to a horse on two legs. Tyrannosaurines are a whole different kettle of
elasmobranchs, what with being so much bigger. Whatever the maintenance
of a similar limb structure and proportion, tyrannosaurines had a whole
lot more to move just a little with the same equipment. We don't
presume they can't move, but that running in these animals would have
been nearly fatal upon slowing, stopping, turning, etc. This makes it
inefficient and unlikely it was a real "runner." Is there a problem
with tyrannosaurs not acheiving mach speeds like their little chicken
mimic relatives?

  [Personally, I find the idea of an Arctometatarsalia more plausible
   than a Bullatosauria, if you get my meaning. The limb mechanics are
   not there for usage, but can be explained as a plesiomorphy in the
   tyrannosaur lineage. One hypothesis, anyway. Troodontids preserve
   the basal maniraptoriform braincase which tyrannosaurs modified,
   and were lost in the maniraptorans. Test, test, test!]

  Farlow and others, Caranno, Caranno and others, Paul, and Holtz all
agree that if tyrannosaurs _could_ run, it wasn't an incredibly fast
run. One ton[ne] in weight is harder to move than 100 kilos, as I
should know having spent a good deal of time unloading worked steel
from trucks a few years back.

Jaime A. Headden

  Where the Wind Comes Sweeping Down the Pampas!!!!

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