Re: Sauropod Biology

[Sim Koning <simkoning@msn.com>]

> From: David Marjanovic

> > Since trees don't grow horizontally, one would expect a Plateosaurus would 
> > stand upright at times to reach high branches.

> One would expect it to get the neck into an upright position. But the rest 
> of the body may or may not have been capable of withstanding such a 
> posture.

Plateosaurus, Massospondylus and other Prosauropods were very front heavy 
animals, which is why they walked on all fours in the first place. They hand 
long necks, large heavy arms and big guts. I would imagine running around on 
two legs, with the torso pitched forward, would be even more of a stress 
than standing upright. The fact that many later (and far larger) sauropods 
retained this ability is certainly evidence that Prosauropods were capable 
of doing the same.


> > Why would it need special modifications to simply rest on the ground and 
> > support some of its weight?

> Because of the sheer weight of the animal, the tail could get damaged 
> otherwise.

Most of the weight would still be on the back legs. I'm not saying that 
these animals put ALL their weight on their tail. The tail was there as a 
counterbalance and possibly to take some of the weight. Obviously if this 
animal could stand on two legs, its certainly not going to need to put a 
whole lot of weight on its tail while upright! The tail would rest on the 
ground, and at the very least would help stabilize the body. The point is 
that these animals were very likely capable of standing upright to reach 
tree branches. Your argument does not make much sense when you consider the 
fact that the animal would be under less stress in an upright position then 
it would be in a horizontal position.

> > I thought they had died out by the end of the early cretaceous too, which 
> > is what I meant >>by "not long after the Jurassic".


> The Early Cretaceous lasted for on the order of 50 million years, so I'd 
> disagree about the "not" part. :-)


A very bad choice of words I admit = P But I consider the early cretaceous 
to be the first 1 3rd of the cretaceous, followed by the mid and late 
cretaceous.  I'm still wrong though, even by my own definitions. the 
Brachiosaurs may have survived more than 50 my after the Jurassic. My point 
was simply that the extremely derived, high shouldered forms seemed to have 
gone into decline after the Jurassic.

And as Tim Williams wrote

> Yes, that seems to be true.  In that vein, Cifelli et al. (2000) gave 
> _Sauroposeidon_ the species name _proteles_, meaning "perfected before the 
> end".