Re: Gallery and Commentary for Copenhagen Mamenchisaurus

[DinoBoyGraphics@aol.com]

>>>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