Re: More on the Massospondylus embryos

[David Marjanovic <david.marjanovic@gmx.at>]

> Galton & Upchurch (in their Prosauropoda chapter of Dinosauria II) regard 
> Saturnalia and Thecodontosaurus as fully bipedal,
> Riojasaurus and the other melanorosaurids (Melanorosaurus, Camelotia, 
> Lessemsaurus), and the remaining prosauropods as facultative
> bipeds. They quote Christian and Preuschoft in suggesting that 
> Plateosaurus was a habitual quadruped which may have used a bipedal
> gait for its fastest locomotion and while standing.

What I wonder about...

Based on their long torsos and short limbs, most Triassic and Early Jurassic 
sauropodomorphs look very unconvincing in a bipedal position. (Interestingly 
*Plateosaurus longiceps* is among the best-looking bipedal runners.) But 
then came the description of *Antetonitrus* which says more derived 
sauropods had their forearms fixed in a pronated position, says that 
*Antetonitrus* could rotate them freely so it could both walk and grasp with 
its hands, and implies that all more basal sauropodomorphs, like theropods 
and crocodiles, had their forearms fixed in a supinated position, though it 
isn't very clear on this. I have trouble imagining walking quadrupedally 
when the hands point laterally. Did the poor beasts walk on their fists, 
like anteaters? Or have I missed something...? ~:-S