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Re: Sauropod Necks

To continue an old thread further, a couple of points:

1. The horizontality of necks in sauropods has only been tested in the diplodocids Apatosaurus and Diplodocus. For those who don't already know, Mike Parrish, one of the two scientists who did these studies using the DinoMorph program (the other scientist is a computer programmer Kent Stevens), is my PhD advisor. I know they plan to do more with more sauropods, but at the moment, all we can say is that it appears that Apatosaurus and Diplodocus could not raise their heads past vertical.

2. Why not? Because the zygapophyses, the finger-like joints that connect the vertebrae together, lock up once the neck becomes horizontal. Further movement beyond horizontal in Diplodocus and Apatosaurus would involve disarticulation of these joints. For those interested in the details, there is a Science article from last year I can provide the ref for if need be.

3. What's the deal with Brachiosaurus, Camarasaurus, etc.? Good question: we don't know yet. Part of the problem with both of these sauropods, the transition between the dorsal verts and the cervical verts is either unknown or poorly preserved. This problem is beginning to be addressed, but it will be a while before a better idea of neck motion in these sauropods is established.

4. Why not rear up on your hindlegs? Many, many scientists, and many, many threads on this list have repeatedly asked, asserted, assumed, or rejected sauropod rearing for many various reasons. The astonishing (to some, perhaps, and certainly to me!) truth is that no one has yet made an in-depth, rigorous study of how a sauropod could rear. Many folks throw around figures about probable mass, the massiveness of the hindlimbs, the shortness of the forelimbs in diplodocids, the height of the neural spines, etc., as "evidence" of rearing up in sauropods, but these are just suggestive and tantalizing guesses of what is really going on. Questions that need to be addressed include: how much rotation is possible of the femur in the hip socket of a sauropod? what muscles are involved and what landmarks can be used to verify that these muscle groups are indeed doing what we suggest? what effect does the large tail muscle (caudofemoralis longus) that pulls the femur back have on a rearing sauropod? did sauropods bend their knees when rearing, and if so, what sort of strain and stress did this send through their pelvis, hindlimb, and foot? sauropods have an open hip socket and a cylindrical femoral head: how was force transmitted through this during normal weight bearing, and could the pelvis and hindlimb handle rearing up? to name but a few that come to mind!

Don't get me wrong: it would be rather cool if sauropods could rear up on their hindlimbs, but it still has to be shown in a way that is testable and repeatable by others HOW sauropods reared up. This is why functional morphology has always been intriguing to me -- it involves more than a cursory glance at a skeleton or a broadly applied assumption. You have to get into the nuts and bolts and try to sort out what's going on to figure out what these big guys were doing.

5. Why hasn't all this been done? What are you people doing with my tax dollars??? Sauropods are BIG. Very very BIG. This has caused mucho problems for everybody involved with them. Until the recent advent of digital scanning technology and microcomputers in general, the only people who had a chance to play with bones in articulation were usually the folks mounting the skeletons. And even here, the bones became locked in static poses. And even with the digital scanning technology, many of the digital scanner are too small to handle sauropod bones. All of us sauropod groupies are waiting with baded breath to get our hands on technology that EASILY allows us to scan 3-D bones. Until then, we're doing what we can with what we got. And we applaud the efforts of the likes of Ralph Chapman, Art Anderson, and many other folks who are working to bring these fantasies to reality.

So how did I get around some these problems? Ahhh ... better wait for my papers to find out. Muha ha ha ha ha (imagine evil laughter). Suffice it to say, when I finally bang off the last sentence in my dissertation, I am turning my attention to finishing a number of long overdue papers!

Adios for now,

Matt Bonnan (the optimistic skeptic and friend to small-brained archosaurs everywhere)

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