Here I must object to the term "grazing" which implies grass eating
and a necessity to eat at ground level. Again, I don't think anyone
is saying that.<<<
Ok, if you restrict the definiftion to "grass," then clearly you
are correct. I was implying "restricted low-level grazing", I
suppose. And while the Cetiosaurus paper was not implying that
Cetiosaurus was a grazer (sensu me), others most certainly have for
diplodocids.
I _do_ think that neck morphology aided in partioning food
resources among sauropods, with for example shunosaurs and
haplocanthosaurs being good at eating low to medium lying food,
camarasaurs having a good medium to high (by mammalian standards)
browsing range, brachiosaurs having a high browsing range. The issue
is that I think the energetic and morphological data supports
diplodocids as extremely high browsers rather than restricted
low-level browsers. Some who strenuously object to this hypothesis
point out (correctly) that no one has quantitatively demonstrated that
diplodocids were designed to do this regularly. But they fail to
mention that the energetics of locomotion, fricition from an elongated
respiratory tract, and increased calories needed just to support that
much extra mass far outways the advantage of being able to "stand
still" during feeding.
So while the question is certainly still open as to why
diplodocids have such long necks that cannot be elevated much above
the shoulders without rearing, (and there could be non food aquisition
selective factors we are ignoring), the evidence is hardly stacking up
in favor of the hooverasaurus diplodocid hypothesis. This (IMHO
falascious) skewing of the data to favor the hooverasaurus hypothesis
is frequently implied via pers. comm. and in papers popular and
professional by Dale Russel, Kent Stevens, Ray Wilhite (my apologies
to Ray if I misspelled that), and on occasion Matt Bonnan.
So perhaps this is a political arguement, in as much as I encounter a
wide array of people who examine the morphological data and ignore the
energetic data, and buy into the press that the evidence is mounting
in favor of habbitual low-level feeding in diplodocids.
Scott Hartman
Zoology & Physiology
University of Wyoming
Laramie, WY 82070
(307) 742-3799