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Re: Bipedal apatosaurs and stegosaurs?



GSPaul writes;

>This notion is going to get me into trouble.

I wouldn't say "trouble."  However, a few hearty disaggreements might
be expected.

> I therefore speculate that Stegosaurus, Apatosaurus and dicraeosaurs
> often walked on just two legs. The failure to use the arms more
> often explains their poor neural controls. Body posture when walking
> on just two legs would have been horizontal, because the hips were
> not modified for a more erect posture (as in therizinosaurs). This
> idea is very difficult to confirm or deny. Even if hindprint only
> stego or apato trackways are found, it remains possible that the
> animals were merely stepping onto their foreprints with the
> hindfeet.

In order for this senario to be accurate, it would require the
animal's center-of-gravity (CG) to be located directly above the hips
(providing good balance).  I'm afraid I don't see this in the mounts
I've observed.  Using the Diplodicus skeleton in the Science Museum of
Minnesota as a reference, it appears that the CG is located at the
animal's lower midsection.  In terms of balance, the only way
Diplodicus could effectively stand bipedally would be for it to rotate
its CG to a point where it would be above the hips.  IOW, it would
have to stand with its spine almost vertically.

Rob Meyerson
Orphan Vertebrate Paleontologist

***
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