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Re: Sauropod feeding



From: crpntr@ix.netcom.com (Kenneth Carpenter )
 > logs in the Morrison does indicate conifers 100 ft (30 m) tall. The 
 > tall size of trees has nothing to do with predation pressures by 
 > sauropods as suggested by one person (sorry, I forgot who). Instead, 
 > height is related to competition for light.

I agree, this is probably the case.

 >   The issue of neck length still seems to bother some (e.g., Friesen 
 > and Paul; no Greg I was not confusing you with Bakker, I would never 
 > insult you in that manner : ) ). Friesen writes (22 Mar) that long 
 > necks of ostriches is to compensate for long legs, apparently a point 
 > made to him by Holtz. But geese, swans and other long necked birds have 
 > short legs. In addition, geese with their broad bills graze from the 
 > ground; maybe they are a better model for diplodocids.

Geese are part of a group that largely feeds underwater.  I suspect the
long neck of the anseriformes may be an adaptation to reaching the bottom
of a pond.  Besides, even in geese, the neck still isn't much langer than
necessary to reach the ground.  It is just that the geese have a tall
*body* rather than long legs.

Thus, geese necks are NOT as long, proportionally, as sauropod necks,
except perhaps for those of such "short-necked" sauropods as Camarasaurus.

Comparing a neck that is only about as long as the main part of the body
to a neck that can be, in some diplodocids, more than twice the length
of the body (excluding the tail) is probably not useful.

I know of very few animals indeed in which the neck so exceeds the
body length.

 > Although Friesen 
 > acknowledges that the broad muzzle of diplodocids is adapted for non 
 > selective grazing, he would have them "graze" from trees - isn't that 
 > selective browsing? After all, the tree only puts out one type of 
 > vegetation product.

Not so. Many browsers are hightly selective, taking only leaves of
a certain age, or lacking insect damage, or only from certain species
of trees, or all three. This is the feeding style of colobus monkeys,
and to some degree, of giraffes. A giraffe feeds by pulling selected
leaves from the tree with its long tongue and flexible lips.
(Watch a film of a giraffe feeding on an acacia sometime - it appears
to be nibbling daintily on the tree).

A camarasaur or brachiosaur would rake in large volumes of leaves
without any selection at all, perhaps stripping whole branches clean
of leaves.  This is more akin to an elephant putting an entire branch
in its mouth and pulling off all of the leaves (I have seen them
do something almost like that - they certainly don`t nibble like
a giraffe).

 >      Greg Paul (27 Mar) argues that the only logical explanation for 
 > long necks is for feeding upwards. I guess then geese and other 
 > short-legged, long-necked birds are illogical (sounds anti-evolutionary 
 > doesn't it? Morris would love it)

Or they evolved the long neck for reaching down into water.
Or they are not as long-necked as sauropods.

Or both.

I doubt sauropods were feeding on the bottoms of ponds.

 >      The latest issue of J. Vert. Paleo. has a paper (I forget who by) 
 > about feeding in extinct camels. The author also notes that the broad, 
 > squared muzzle species were grazers and the pointed muzzle species were 
 > browsers. This is the same point I was making with sauropods - i.e., 
 > niche partitioning.

Yes, niche partitioning, naturally.  It is impossible for so many
sauropods to have co-existed as we see in the Morrison otherwise.

But it can be done in the trees as much as between trees and ground.

Giraffes and elephants coexist, and overlap in their feeding heights
to some degree.  Giraffes are mosre selective, elephants less so.
Giraffes, on average, feed higher, and elephants tend to feed lower.

In the same areas there are also baboons, chimpanzees, and in some areas
elephants coexist with leaf-eating monkeys.  The simple fact is that
most mammalian selective browsers are arboreal, so they have no need
of a long neck.

However, there is little (read none) evidence for arboreal leaf eaters
in the Late Jurassic (multituberculates being seed and fruit eaters).
This means there was less competition in the trees for food than there
is now - unless the sauroods took up the slack. It cerainly means that
there was a wider scope for niche partitioning among long-necked browsers
than there is now - since they must now compete with arboreal browsers.

 >      By the way, at the WAVP meeting, it was demonstrated that the 
 > holotype vertebra of Ultrasaurus (brachiosaurid) is a posterior dorsal 
 > of Supersaurus (a diplodocid), a pointed conceded by Jensen who at the 
 > meeting.
 
Umm, *which* Ultrasaurus?  The Japanese one? or the American one that
is more properly called Ultrasauros?
                                 ^^

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

The peace of God be with you.