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Re: galloping sauropods?
>>>I've seen some depictions of Brachiosaurs in a giraffe-like gallop, and
some drawings of galloping ceratopsians, but no art showing a gallop/run
for any other type of sauropod. Is there any reason for this, or did I
miss some galloping sauropod pictures somewhere? Is there any
physiological objection to galloping/running sauropods? I've read a
little bit about the locomotion of the large dinosaurian quadrapeds, but
most seem to focus on the ceratopsians.<<<
First, where did you see a galloping brachiosaur picture? Doug Henderson
has done a picture of some brachiosaurs hurrying away from a twin tornado,
but they are portrayed in the correct "running-walk," attributed to these
30+ tonne behemoths. While giraffes actually gallop (wherein all limbs
are off the ground at some point in the stride), animals like elephants
use the running-walk as their fastest gate. The name basically explains
the mechanics; the animal is walking as quick as it can. This can be very
impressive, as elephants reach speeds of 25 mph.
To quickly answer your second question, if you look in Robert
Bakker's article in "The Continental Jurassic" volume from Arizona, he
drew a cetiosaurid dinosaur that looks all the world (two me) like it's
galloping. It's two forelimbs are in the air anyway, and it is certainly
doing something very athletic. I don't think that Bob actually suggests
that sauropods galloped (at least, he's never confessed this sin to
me...), so I'll have to ask him next time I see him.
Finally, it's very unlikely that sauropods could gallop. Unlike
other quadropedal dinosaurs, (except possibly stegosaurs) sauropods are
graviportal and posses fixed ankles. Being graviportal (animals with
straight, column-like limbs) doesn't mean that you can't run, after all,
you have a graviportal limb design. But it does mean that the shock from
impact with the ground is tanmitted right up the limb into the hip socket.
Since bone doesn't compress (much), and there isn't enough cartilage to
absorb the shock, it's quite tramatic on your body. Humans, being small,
can get away with it (for a while, anyway, recall how many athlete's end
up having knee and hip problems in older age), but I doubt very much that
a ten tonne sauropod (let alone a much bigger one) could.
More condemming yet is the fixed ankle. Humans do, at least, have a
mobile ankle joint that can move through `80 degeees of arc. This allows
us to propel our bodies into a suspended ballistic fase. Sauropos doen't
appear to have this adaptation, so there would be no way for them to
propel themselves into a gallop. I haven't had a chance to play with
stegosaur limb bones yet, but they don'tr appeat to be very mobile either.
Nodosaurs also have very short ankles, although they look to me like they
retain the full range of movement typical to ornithiscians. Perhaps Dr.
Kirkland would have more info on that. Anyway, I'm not sure what that
would mean for nodosaurs, but certainly they weren't galloping quickly.
I hope this helps.