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Re: T.rex and elephants

Moi is the one who has pointed out that the inflexible ankles (due to
flattened astragalus, as described by Osborn/Gregory) and short feet of
elephants, and tortoises for that matter, prevents them from running. Believe
I said so in DinosPast&PresentV2(1987) and PDW, will restate in an upcoming
paper on locomotion in ornithomimids and tyrannosaurs. A longer hindfoot with
a flexible ankle is needed in order to propel the body into a suspended
phase. This can be tested by trying to run on your heels alone, keeping the
rest of the foot clear of the ground. The most one can do is do a sort of
bipedal amble, cannot push off into the air. Virtually all amniotes with
flexible ankles can run, those with fixed ankles cannot. One of those obvious
things everyone missed while doing all those comparisons of limb ratios, bone
bending resistence, etc. Because sauropods and stegosaurs had very short feet
and little ankle mobility they probably could not run. All other dinosaurs of
all sizes had mobile ankles with longer feet and probably could run. 

Ornithomimids and tyrannosaurs had bigger ilia than other theropods of
similar size. Their limbs were longer and more gracile as well. This suggests
or & ty could run faster than other theropods.