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Re: T.rex and elephants

Jonathon Woolf wrote:
> John R. Hutchinson wrote:
> >
> > Sean Connell writes:
> >
> > >And elephants can't run due to the construction of their ankles.
> >
> > Do you have a reference for this? I'm working on elephant locomotory
> > biomechanics and have never come across a ref that corroborates that.
> I don't know the reason why, but I know I've read that elephants cannot
> run, if by "run" you mean the gait known as a "run" in dogs and a
> "gallop" in horses.  I kinda thought it had more to do with shoulder
> movement and sheer mass than with ankles, though.
> > Well, I can't. For one, elephants amble (not run; different gait and
> > different mechanics) on four legs, not two. I don't have the ref to support
> > this, but I think it's farily safe to say that most of their weight is
> > supported on their forelimbs, too. I don't find it easy to compare
> > theropods and elephants in terms of anatomy, although the overall hindlimb
> > mechanics of large theropods and elephants might be similar, who knows?
> Seems reasonable to me to say that the forelimbs are the main
> weight-bearing limbs in elephants.  After all, you've got that great
> awkward head and tusks up front, and not much behind to balance it.  

        I was of the opinion that the weight distribution of an
elephant was fairly even between all four legs, with the centre of
mass somewhere between the front and hind legs. Elephants can support
themselves entirely on their hind legs, and in the circus they are
taught (made?) to balance on their heads and front legs only. I
suspect that the longer front legs may help increase the normal
foraging height of the trunk, perhaps in a similar fashion to
that of brachiosaurs. 
        Rhinos also have large heads, but they are held
low. Rhinos also tend to feed lower to the ground. This begs the
question: does the height of the food eaten control the height at
which the head is held, or is the head held at a certain height for
structural reasons and the diet has to conform to biology?
Were sauropod necks long to feed high up, or did they feed high
up because their long necks made low browsing difficult? It may
be a chicken and egg thing, with both sides of the argument developing
        Dann Pigdon
        Melbourne, Australia