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Re: Sauropods



>From: ornstn@inforamp.net (Ronald Orenstein)
 > A thought about this: the prosauropods (as sometimes restored) appear to
 > have been somewhat bipedal (is this actually true?) 

Yep.

 > If the primitive
 > sauropod condition included bipedality (I mean early sauropods - I know that
 > dinosaurs in general are suposed to have arisen from bipedal ancestors) a
 > horizontal neck would be the expected condition, as adopting the bipedal
 > posture would be all that was required to place the neck in a vertical
 > orientation. 

Exactly!

Almost nobody questions the upright feeding posture of prosauropods.
The *standard* reconstructions of Plateosaurus is a picture of it
standing on it hind legs feeding on a tree. Nobody complains about that.

Except for details of foot and vertebral structure, Cetiosaurus
is almost identical to prosauropds.  And Diplodocus differs mainly
in features relating to its *extremely* long neck - at least at
the gross morphological level.

Yet, despite this basic similarity, many people balk at showing
Diplodocus rearing up.

 > And just to show that I'm not convinced of this, it doesn't apply to the
 > gerenuk, which can certainly hold its neck bolt upright when not standing on
 > its hind legs.  Of course that may help it spot predators, and a gerenuk is
 > basically a quadruped, not a biped.

Part of what is going on here, however, is retention of ancestral
characters.  The ancesters of the gerenuk were probably *grazers*.
The general structure of the gerenuk is retained from the ancestral
antelope.

This is why I can believe that *some* sauropods, at least some of
the less extremely long-necked forms, may have secondarily switched
to fern grazing.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.