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SOME STUFF ON SAUROPOD NECKS
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.
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.
In the Morrison Formation, there are ten different species of diplodocoid
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
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.
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
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
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
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.