Re: sauropod necks-buckaroobwana is back! ha ha ha ha ha !!

["Matthew Bonnan" <mbonnan@hotmail.com>]

Buckaroobwana said:
> This has probably been discussed before, but could sauropods raise their
> necks up into a vertical position?

Yes, many times.  As Justin Tweet already mentioned, work by my advisor (J. 
Michael Parrish) and Kent Stevens (who programmed DinoMorph, the program 
which allowed them to articulate the vertebrae in cyberspace) has shown that 
the diplodocids Apatosaurus and Diplodocus could not raise their necks 
beyond a horizontal position.  This is so because the zygapophyses (the bony 
joints between the vertebrae, not to be confused with the vertebral discs) 
lock up when the cervical (neck) vertebrae are raised into a horizontal 
position.  The computer model essentially modeled these joints based off of 
careful measurements of the zygapophyseal surfaces by Parrish and Stevens on 
Diplodocus and Apatosaurus specimens.

There appears to have been a surprising amount of lateromedial (side to 
side) motion in the necks of these guys, however, and Apatosaurus can 
ventriflex (bend its neck downward) its neck such that its head would be 
looking underneath its feet!  Of course, this is only possible in cyberspace 
with no ligaments, muscles, and connective tissues accounted for, but the 
downward flexibility of the neck in diplodocids is extraordinary.  This 
suggested to Parrish and Stevens that diplodocids may have been grazers.

In Camarasaurus, the jury is still out.  Parrish and Stevens tried a 
preliminary attempt at modeling that neck, but the darn thing did not seem 
to want to get above horizontal either.  However, they are currently looking 
this over, as it seems that Camarasaurus may have had a more vertical neck.  
Brachiosaurus did have a relatively vertical neck, but not as tightly kinked 
a one as you see in most illustrations (e.g., Greg Paul's Brachio herd or 
muscle restoration pics show the neck much too vertical -- in those 
positions, the vertebrae are literally disarticulated from one another -- 
just an example, not to pick on Greg Paul who, in my opinion, is a fantastic 
dinosaur artist).

As far as endothermy/ectothermy in sauropods, well, who knows?  We don't 
have the information or complex enough computers to accurately model 
physiology in living archosaurs, let alone sauropods.  The current evidence 
seems to suggest that dinosaurs grew fast, but we also see LAGs (lines of 
arrested growth) in dino bones as well, a trait not usually seen in 
endotherms but seen commonly in ectotherms.  In any case, perhaps sauropods 
and most dinosaurs were in a physiological category by themselves.  I tend 
to think dinosaurs were endothermic but only in terms of muscle energy and 
in terms of having more fine control over their homeostasis than, say, a 
typical "reptile."

I would doubt sauropods were "hot-blooded," high-speed critters, but I would 
also doubt sauropods were simply big "cold-blooded" archosaurs maintaining 
constant heat through bulk.  Bulk homeothermy, as well as Bakker et al.'s 
dinosaur endothermy, seem to be too simplistic of concepts for temp control 
and physiology in dinosaurs.  Plus, it's difficult to devise tests for these 
sorts of questions.  Unfortunately (and I mean this -- I wish I had a time 
machine to solve this whole mess), we have not yet hit on a way to ascertain 
with a rigorous degree of certainty the physiology and metabolism of 
dinosaurs.

Hope this helps,
Matt Bonnan

A number of books by Knut Schmidt-Nielsen deal with animal energetics and 
physiology, and you may wish to visit your local library to check these out. 
 Schmidt-Nielsen is probably one of the best popularizers of animal 
physiology and metabolism, and is a good place to start.

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