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From: GSP1954@aol.com

 > ...    The necks of sauropods were extraordinary in length and
 > complexity.  Extraordinary selective pressures were necessary for
 > evolution to produce such necks. Avoiding burning a few kcals to move
 > a few meters is not an adequate explanation.

Especially when you factor in things like the difficulty in pumping
blood through the neck (even held horizontally there would be substantial
frinction induced resistance), and the energy taken to hold the neck
up (even with the ligaments, some energy cost is present in supporting
the neck).

I think the energy and growth costs of the above two items alone
exceeds the cost of taking a few steps!

 >  The only logical explanation for the extraordinary length of
 > sauropod necks is to give them the ability to reach beyond where
 > short necks could, which is only upwards. ...

At least for graviportal terrestrial animals.
[The cost of movement in water is higher, and the balance point
may shift in that case].

 > ... The diplodocids were the most trophically flexible sauropods in
 > the Morrison. Their ability to stand (but not walk) tripodally, and
 > long necks suggest they got most of their food from the medium to
 > taller riverine trees (8-20 m), which were the most dependable
 > source of food because they tapped into ground water available year
 > round. ...  An absence of 100 m tall trees in the Morrison is not
 > important because no sauropod was that tall.  Likewise, giraffes
 > often live on grass plains with scattered medium sized (3-8 m)
 > trees. In fact, giraffes and elephants inhabit the Namib desert,
 > were the only browse is riverine trees.

Overall, I suspect that the modern elephants are the ecological
equivalent of the camarasaurids - mostly mid to mid-low browsers.
The main difference is that instead of an expensive long neck they
have a relatively cheap long nose.

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

The peace of God be with you.