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Re: Blood flow in Sauropods



>From: jdharris@lust.isem.smu.edu (Jerry D. Harris)
 >...  I can't see a real reason for most sauropods to
 > assume a tripodal stance 

For *most* sauropods this is true.  For diplodocids the story
is different.  The diplodocid neck was held *horizontally*.
What blinking good does a long horizontal neck do? (And given
the *extreme* length of some diplodocid necks, it must have had
*some* purpose).  However, by standing on their hind legs that
horizontal neck becomes a vertical one.  Now it accomplishes
something.

 > (stegosaurs are a little easier to imagine doing
 > this) -- I mean, how tall are the trees in the Late Jurassic supposed to
 > have been?!?  Trees in the African savannahs are taller than elephants, but
 > you don't see them rearing up to get their trunks into the higher parts of
 > the trees;

This is true - but elephants aren't specialized in the same way as
sauropods.  it is giraffes that are the closest we have to sauropods
today.  They *do* feed in the tops of trees.  Remember, to evolve
a long neck, it had to have some function - one sufficient to
outweigh the disadvantages, like blood pressure requirements.

Also, the modern savanna trees are really quite short, even by
comparison to most *living* trees - few exceed 40 ft, I know of no
true savanna trees that exceed 60 ft. (Some riparian trees in savanna
zones may be taller than this however) The presence of giant conifers
in the same areas as the sauropods is strongly suggested by the fossil
record.  Modern giant conifers are among the tallest living trees.

 > I don't see sauropods rearing to get their trunks (essentially,
 > the whole neck) up into a tree.  

For most sauropods this is true - the necks are *already* up there.
For diplodocids this is not true - they have to do something to get
the necks up there.

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

The peace of God be with you.