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Re: Speed in giants and cursors



<< Contrary to common claims (incl a Harvard researcher on
NPR), elephants do not establish that large animals cannot
run for two reasons: they cannot run at any size, and they
cannot run because they are not designed to. If elephants
could run when they are the size of horses and lost the
ability as they grew up that would be one thing. But they
are as unable to run when young as when grown up.>>

Yes, I remember an old post in the DML archieves stating
that even Juvenile elephants could not run. Perhaps rhinos
outrunning horses could indicate that size does not mater
all that much ... But we don't have many examples of large
animals running. Judging from what I have read, rhinos don't
make it much higher than 2,000-2,500 kg.

<< All living animals that have such limbs can run fast, so
John's opinion is at best speculative as well as doubtful,
and the burden is absolutely upon those who wish to show
that cursorial features will evolve among, or be retained
by, nonrunners.

<< As Tom H noted the limb ratios of tyrannosaurs are,
contrary to propoganda to the contrary, in the high range
usually associated with running. The tibia/femur ratio of
tyrannosaurs including T rex were similar to those of
horses - all the are more remarkable since the theropods
were so much bigger - much higher than those of similar
sized rhinos, and far exceed those of elephants. A strange
pattern for animals that did not run.>>

Let's also mention the knee crests, they are exeptionnaly
large in _Tyrannosaurus_. Side note :(However, I do not
agree with the statement made by someone early that
Allosauroids did not have those knee crests. Ture, but
that's because the overall tibia in _T.Rex_ is thinner, and
by the end of the tibia, the knee crest "blows out". In
_Giganotosaurus_ or _Acrocanthosaurus_, the tibia is general
more massive, and such the "knee crest" is there all along
the way and does not "blow out" at the end like in _T.rex_,
which might give a wrong impression. I'm sure if we
compaired both circumferance at the end of the tibia, it
would end up being similar).

Coming back to the topic : What might prove the importence
of cursorial adaptations would be by compairing two very
similar modern animals, but having very different body
weight. Maybe ...

Thomas Miller

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