re: Sauropods and lung development

["Jaime A. Headden" <qilongia@yahoo.com>]

Scott A. Hartman wrote:

<Actually, while the weight reduction advantage of pleuoceols has been
advanced by authorities ranging from _When Dinosaurs Rule the Earth_
to Jack Macintosh, I doubt that this was their main function.>

  Just to elaborate, there are two main functions proposed for
sauropod pleurocoels: aiding in blood pressure and flow, and
weight-saving. Either could be correct, and both together may be
correct.

<Both Indricotherium and Mammuthus grow to average sauropod sizes, and
neither shows any tendancy toward the enginnering marvels that
sauropod vertebrae became (has anyone besides Greg Paul taken the time
to compare the dorsal vertebrae of sauropods and mammals of equal mass?>

  There are few large mammals that equal (or equalled) the mass of any
of the sauropods, though *Amaragasaurus* and *Mammuthus premigenius*
came close to each other. I really haven't taken a look at
*indricotherium*, because I can't seem to find a book-type publication
with it in there, and don't know of any refs for a journal.

  However, the cervicals of either are too dissimilar, for, as I have
taken a gander at the necks of rhinos, elephants, giraffes, deer,
horses, and bison. The first two have a neck that is horizontal,
mainly to support that massive skull at the end, a diagonal neck would
be . . . inefficient. Reduce the size of the skull, perhaps, and then
you're cooking. That's what the other animals have done. Their skulls
are nowhere near as massive as the first two, so there is efficiency
in making a longer neck, and less need to excavate the vertebrae.

  Likewise, the size of the vertebrae are also differentiary: sauropod
vertebrae (using diplodocids) are, I belive, on the average of about a
two feet long, and four feet high with the neural arches and spines,
and a foot or so wide, with the diapophyses. Elephant vertebrae and
giraffe vertebrae are far smaller. There is no need to excavate them,
for they are also far lighter. As for circulation, only giraffes would
conceivably have a problem with that, and they don't, they manage
quite well the way they are, wether they are at neutral in their
diagonal angle, or upright.

<The sauropod verts are faaarrrrrr more robust. An interesting trait
in critters with a supposedly less active lifestyle). Anyway, I
suspect that the pleurocoels primary function was the same as it was
in their ancestors; respiration. The fact that sauropods elaborate the
system to a greater extent then many theropods and birds is probably a
reflection of the rigourous aerobic demands of combining long necks
with gigantism.>

  Perhaps a comparison of some massive theropod, say *Giganotosaurus*
for whom cervical centra are known, and a primitive sauropod or
prosauropod, as I believe even *Barapasaurus* and *Shunosaurus* have
excavated centra.

  It's worth it, but until I get my hands on "super-theropod" papers,
I won't be able to perform this myself.

==
Jaime A. Headden

Qilong, the website, at:
http://members.tripod.com/~Qilong/qilong.html
---
All comments and criticisms are welcome!

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