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RE: Evolution of tyrannosauroid bite power



Patrick Norton wrote:


>> Because there wasn't much selective pressure acting on them?
>
> "Much" is a relative term too, although I agree that the jaws (and neck) and
> hips were probably playing a much larger role in prey/carcass acquisition in
> T. rex than were the arms. Relative to the animal, and the probable size of
> its prey, T. rex arms were small and weak.


The arms were certainly small.  But it does not necessarily follow that they 
were weak...


>From Carpenter and Smith (2001):


Abstract: "Although proportionately the forelimb is very small, the mechanical 
advantage reveals an efficiently designed force-based system (vs. a 
velocity-based system) used for securing its prey during predation. In 
addition, the M. biceps is shown to be 3.5 times more powerful than the same 
muscle in the human, the straight, columnar humerus provides maximum strength 
to mass ratio to counter the exertion of the M. biceps, and the thick cortical 
bone indicates bone selected for ultimate strength. Such mechanical adaptations 
can only indicate that the arms were not useless appendages, but were usted to 
hold struggling prey while the teeth dispatched the animal. _Tyrannosaurus rex_ 
was therefore an active predator and not a mere scavenger, as has been 
suggested."



Cheers

Tim
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