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Re: Bipedal apatosaurs and stegosaurs?



On Sun, 6 Oct 1996 GSP1954@aol.com wrote:

> This notion is going to get me into trouble. 
> 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. 

        Yes, the use of mind-altering substances can get you in a lot of
trouble ;)
        It's difficult to imagine this, but then, it's also difficult to
imagine 30 tonne animals rearing up to feed, or 30 tonne animals period.
It raises an interesting question- whether they could at all-
I suppose there's no reason why not but it seems like an impractical way
to go for long distances. But then, hell, 20-30 tonne bipeds- duckbills-
seem to be possible. But it also seems to me that their forelimbs are much
more slender than in stegosaurs and diplodocids. 
        Could the smaller nerve pathways, in
part, be simply due to a smaller muscle mass to supply with sensory and
motor nerve endings? Or the fact that they might have spent a lot of time
sitting on their tails? This suite of characters are what is cited for
evidence of tripodal feeding. 
        Doctor Bob made another observation- that some of these animals
(Stegosaurus, Apatosaurus) share big deltoid crests. He suggested they
were used to maneuver the animals- push off sideways and spin around
quickly to defend against predators. When I initially heard about the
nerve stuff, it made me a little more skeptical of this. But the
observation is an interesting one, still... deltoids are used when
pushing. I wonder if they couldn't be used to push down instead
of sideways. This would be helpful in rearing back on the tail. How are
the deltoids in Dicraeosaurus, Amargasaurus, etc?
        
        Nick Longrich