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After reading everyone's thoughts on sauropods, I've decided to put all my
ideas regarding them into one post. I'm not pretending to be a scientist
here, I just want feedback on my ideas to see if they are plausible.
I think to get a general idea on sauropod lifestyle, we should NOT look at
giraffes, or elephants or anything mammalian for that matter. The animals
that should be compared with sauropods are their ancestors, the
prosauropods. Consider Plateosaurus, this animal was not a high browser or a
low browser, it was both. This animal was the first dinosaur to graze from
*trees* high above the ground. It reared up onto its hind legs and used its
large thumb claws to pull down branches, not unlike later therizinosaurs or
giant ground sloths. The long neck was clearly an adaptation for high
browsing from trees while in a *tripodal* position. Plateosaurus was also
fully capable of low browsing. This was likely the key to sauropod success,
the fact that they were able to feed from the ground equally as well as they
could feed from the tree tops. Sauropods were probably generalist herbivores
that could feed from any level. This may have been what allowed them to grow
so large in the first place. Now, after considering the above, you will see
that most sauropods retain most, if not all the same adaptations of their
ancestors, only taken to the extreme. Is it really logical to think that
despite having all the same adaptations of their ancestors, that their
strategy for survival would have changed back into something less
advantageous. With these things considered, it makes perfect sense that the
neck's neutral pose would have been horizontal. If the NP was too high, then
it would be a specialist high browser and would be less effective as a low
browser and vice versa.
How did sauropods get blood all the way up to their tiny heads? To simply
say that it was not possible for them to elevate their heads so far above
their hearts, because a giraffe like system would not work, is cutting
evolution a little short. Evolution has this wonderful way of coming up with
many different solutions for the same problem. Look at bats, birds,
pterosaurs and insects, they all fly, they all have wings, but they all have
very different ways of doing it. There is no more reason to think sauropods
evolved the same solution as giraffes instead of something completely
different. The most likely explanation (in my opinion) is that they used
peristalsis to move blood to their head. This type of system would not
require extreme blood pressure. This type of pumping action is used in the
digestive tract, oviducts and many other tube like organs found in animals.
This system was probably the ancestor of the modern closed circulatory
systems found in vertebrates. Annelids still use peristalsis to pump blood
through their bodies. This system would have disadvantages though. There
would be the possibility of back flow and the amount of blood that could be
"carried" to the brain would probably be limited. This type of system would
also require constant muscular action (like a heart) which would burn
energy. This could explain why the brain is so small and why the neck's NP
was horizontal. If the neck was at rest in a horizontal neutral position,
the peristaltic system would not be needed until the head was raised again.
There were probably specialist sauropods such as Brachiosaurus and
Dicraeosaurus. With its high shoulders, Brachiosaurus was likely a high
browser like giraffes and Indricotherium, while Dicraeosaurus, with its
*short* neck, was a specialist low browser. As with all specialists, these
forms were prone to extinction, which is probably why the Brachiosaurs died
out not long after the Jurassic.
So, in the end, what I am speculating is that Greg Paul and Kent Stevens are
both right. I am suggesting that sauropods were not giant giraffes,
elephants or cows, they were sauropods!
Please share your thoughts...
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