Re: Sauropod Necks

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

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)

"If you don't like dinosaurs, UPPER JURASSIC!"
-- slogan from a geology T-shirt
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