Re: MORE ON SAUROPOD FEEDING HIGH & LOW

[Stan Friesen <swf@ElSegundoCA.ATTGIS.COM>]

 > On Wed, 27 Mar 1996, Stan Friesen wrote:
 > > 
 > > At least for graviportal terrestrial animals.
 > > [The cost of movement in water is higher, and the balance point
 > > may shift in that case].
 > 
 >      I would be interested in hearing exactly how Elasmosaurus used 
 > it's neck- snaking through the water, or plunging in from above?

How would one tell?

Actually, given that some plesiosaur skeletons are from many hundreds
of miles from the nearest known land, this at least rules out feeding
from shore.

 > > 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.
 > 
 >      Bakker makes the comparison between elephant trunks and 
 > diplodocid necks and heads. Like an elephant trunk, the main function of 
 > the neck is to strip off leaves so they can be processed further down (by 
 > the jaws in elephants, and the gizzard in brontosaurs). The skulls and necks
 > have been reduced down to the bare minimum necessary, so that the amount of 
 > bone, muscle and brain supported by the skeletal and circulatory systems 
 > is minimized. Sauropods actually evolved smaller brains to reduce the 
 > amount of blood needed in the head.

I'm glad to see that Dr. Bakker agrees with me about the function
of the elephant's trunk :-)

All of these facts show out how expensive (in physiological terms) such
a long neck really is.

Whatever factors drove its evolution, the selection pressures must have
been substantial.

 >      It would be interesting to know, however, how much low-feeding 
 > the sauropods did, or if there were any grazers.

Some, at least, could well have been rather opportunistic, much like
an elephant today (which will eat grass if nothing else is available).

 > Stegosaurs look like they'd be particularly good at this,

Not really.  They have an extremely narrow snout!
This means they were very selective feeders.  This rules out
grazing per se. (Given the muzzle structure of Stegosaurus, I
suspect it may have had a long prehensile tongue, like a giraffe).

 >  even though they show so many 
 > adaptations for tripod-feeding. Odd that they never did evolve long necks 
 > like diplodocids, perhaps a greater proportion of their diet came from 
 > grazing than in diplodocids. 

More likely they browsed lower than any sauropod normally did.  Then,
in the presence of sauropods, competitive exclusion would tend to keep
then down low.  (As a general rule animals with similar food requirements
parition the search space in an area - this means each species of
sauropod would have a distinct characteristic feeding height, and so
would Stegosaurus).

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

The peace of God be with you.