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Re: Do not misunderestimate the king was Re: Evolution of tyrannosauroid
Thanks, David. There is much new data in Lipkin and Carpenter's paper
T rex book due out soon. The evidence includes various pathologies
fractures, fractures, muscle avulsions of the humerus) that it it
the forelimbs are placed under a great deal of stress. Remarkably, the
incidence (as %) of these pathologies of JUST the forelimb bones
coracoid, and furcula) is highest of any theropod...
...Thus, the new evidences from the entire forelimb system of
T rex show the forelimb was used actively.
Very interesting stuff! One thought to toss out, though: given the
extremely high incidence of pathologies, is it conceivable that the
arms were 1) used actively but 2) not actually terribly important.
That is, Lipkin and Carpenter obviously show that the forelimbs were
subjected to substantial loads and thus were not kept out of harms way.
At the same time, the safety factor was apparently quite low, as the
forelimbs were regularly being pushed beyond their failure points.
This suggests to me, at least, that the arms were not under strong
selection for increased resistance to load. Safety factors do vary, of
course, but they appear to be pretty consistent within clades, based on
the work published so far. The fact that tyrannosaurs seemed to have a
strangely low safety factor makes me wonder a bit.
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181