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RE: Bipedal apatosaurs and stegosaurs?



Peter Buchholz writes;

>Actually, the extremely long tail of Diplodocoids probably placed the CG
>somewhere almost directly in front of the pubes, not way up under its heart

Close, but no soup for you.  In spite of the tail's length, the muscle and
 bone appears to be kept to a minimum, which would reduce the total weight
 of the tail considerably.

>You also seem to forget that all bipedal animals are constantly
>correcting their posture so that they don't fall over.

Perhaps, but the CG in these animals is kept as close to the hips as
 possible, to reduce any unstability.  For a tripodal sauropod, the CG would
 be *considerably* higher than the hips.  Here's a cool model: Take a
 fishing rod; now try to keep the tip steady while holding the reel end;
 t'aint easy is it.  A rearing sauropod would have the same trouble.

>What I am saying is that Diplodocoids were probably too long and
>straight to have survived in a semi-dense forest, so tripodal
>feeding and perhaps bipedal walking, were the only ways they could
>manoeuver around in the forest.

I admit that this would be a problem, but I figure that a hungry diplo
 wouldn't be too picky about any particular tree, and just eat anything that
 was easily accessable.

>Actually, a 90' Diplodocus would not have it's head at the very tops of the
>trees, unless of course you're advocating that they bounced on the tips of
>their tails Tigger-style...  It's head would maybe be about 30'-40' high, not
>the 70'-200' heights that mature evergreen trees reach (and I assume did
>reach).

Even if they weren't at the very tops of the trees, conifers (as well as
 most trees, now that I think about it) have an annoying habit of
 becoming rather sparse near the very top.  In terms of plant volume,
 Diplo would be better off staying planted (no pun intended) on the ground.

>Well... that's very lucky for the Allosaur IF it got in close enough to the
>Diplodocoid without being seen or heard.  This is random speculation, but I
>would think that perhaps they had fairly well developed ears.  Anyways, why
>also, do you assume that Diplodocoids were sloth-slow?  Just because they
>couldn't walk very fast, doesn't mean they couldn't MOVE very fast.

The speed and senses of the animal would certainly help Diplo's position,
 but remember that African wildebeast excell in both, and they are taken out
 by lions and hyenas on a regular basis.  If Allo was an ambush predator, it
 would be able to get close to the diplo herd long before the animals were
 aware of it's presence.  With that kind of threat, the animal would want to
 keep itself well planted (like a martial arts   master) to be ready to deal
 with the predator at a moments notice.


Rob Meyerson
Orphan Vertebrate Paleontologist

***
"If anything is going to go wrong, it'll happen at maximum velocity."
                        -Red Green