SOME STUFF ON SAUROPOD NECKS

[Tetanurae@aol.com]

Ok, I know the thread has wound down, but I have some time on my hands to 
actually write something now, so here goes.

I think some of the arguments in support of the vacuum cleaner hypothesis are 
at best unsupported, and sometimes bordering on nonsensical.  I am going to 
focus mostly on the Morrison Formation because it's still probably the best 
known sauropod fauna on Earth.

FOOD SUPPLY
Did sauropods feed in the trees in the "grasslands?"  I don't know, but I think 
that someone with more data than I can figure that without much calculation.

It should be a no brainer, however, that a forest with a canopy of 10 m should 
have approximately ten times as much plant food as a "grassland" of about 1 m.  
Given the biomass of sauropod dinosaurs alive at any given time and estimated 
metabolic rates one could calculate the amount of food needed to be eaten in 
the fauna.  I suspect when one gets done with that, the results will firmly 
state that sauropods could not survive on weeds.

Which brings me to my next topic of discussion: forests.  I read some emails 
on-list stating that sauropods standing still and having a long snakey neck to 
eat vegitation on low trees would be advantageous.  I then wonder to myself if 
many people onlist have ever been to an actual gosh-darned real forest with 
trees and everything, because if you had, then you would quickly see that if 
you say stand in one spot and hold a 5 m beam in front of you and try to swing 
it in a semi-circle you hit stuff.

COMPETITION
In the Morrison Formation, there are ten different species of diplodocoid 
sauropods:
Diplodocus longus
D. hayi
D. carnegeii
Barosaurus lentus
Seismosaurus hallorum
Apatosaurus ajax
A. louisae
A. excelsus
A. yahnapin
Amphocoelias altus

Although not all ten known species were sympatric, there were many that were 
sympatric and might have been in direct competition had they all eaten 
ground-level plants.

One possible clue in determining who was eating what is to look at dentition, 
because if the dentition of closely related sympatric species differs, they 
probably were eating different things.  Strangely enough however, the dentition 
of all known diplodocoids (with the exception of Nigersaurus) is shockingly 
similar.  Diplodocus, Apatosaurus, Barosaurus and Dicraeosaurus have skulls and 
teeth that were very close to identical.  This suggests that these animals were 
eating the same types of food and - if feeding on the ground - would have been 
in direct competition with eachother.

NECKS
If you look at modern low browsers, they have comparitively short necks.  In 
fact, the length of head + neck is always slightly longer than the shoulder 
height.  Diplodocoid sauropods display something totally dissimlar to this 
however: necks that are much longer than their shoulder height.  Additionally, 
the neck lengths vary by genus, from longest to shortest: Barosaurus, 
Diplodocus, Apatosaurus, Dicraeosaurus.

Also, recent studies show that diplodocoids could not only reach their heads to 
the ground, but could also put their heads several meters under it, if given 
the chance.  If I recall correctly, there is very little latteral flexion 
allowed by the cervical vertebrae, contrary to the stationary vacuum hypothesis.

WHAT DOES IT ALL MEAN THOUGH?
Odd you should ask :-)  But I believe that combination of the following factors:

1) Sauropod biomass was probably too high for diplodocoids to survive on weeds 
alone
2) Forests are dense and difficult to move big things in
3) There is little if any variation in the feeding apperati of diplodocoids
4) Diplodocoid necks are not only very long, but differ in length according to 
genus
5) Diplodocoids could flex their necks forward so far that if on the ground, 
the neck would reach deep into the substrate
6) Among sauropods, diplodocoids have the longest, heaviest, and most stoutly 
constructed tails

indicate that diplodocoid sauropods were not only feeding in trees, but feeding 
high in trees and avoided directly competing because rearing sauropods with 
differing neck lengths would not have been feeding at the same level.

Pete Buchholz
Tetanurae@aol.com