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

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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