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Sauropod necks thread continued ...
It disturbs me that the model does not want to get _Camarasaurus_ necks
the horizontal: it was CLEARLY capable of such without disarticulation, as
documented by numerous fossils in opisthotonic death position: the CMNH
juvenile, the USNM specimen on display, etc.
Whoa, don't get me wrong here. No, no, no. Of course it would be
disturbing if they were using the model alone to predict neck placement! I
don't think I was too clear.
First off, they have modeled a giraffe neck in DinoMorph, and that went
together and moved like a giraffe neck just using zygapophyseal info.
Furthermore, the real preliminary stuff on Brachiosaurus (which was shown in
the Discover magazine article) showed a relatively vertical neck, so again
it's not like the program is somehow forcing everything to be horizontal.
However, take a look at Osborn and Mook (1921) and in that monograph, on a
number of sauropods but with a lot of info on Camarasaurus, you find a
restoration of the Camarasaurus skeleton -- and that restoration has the
neck in a relatively horizontal position. Now, Osborn, Mook, and the other
grand old men of paleontology had access to these vertebrae before they were
mounted, and perhaps in Camarasaurus, the vertebrae don't like to extend far
beyond horizontal, again constrained by their zygapophyses.
Yes, you point me toward the CM and UMNH Camarasaur specimens. In both
cases, as you note, the neck is cranked up in a death pose. Note,
especially in the CM sauropod, many portions of the skeleton are
disarticulated -- the scapulacoracoids have dropped down, the humeri are
turned in, the antebrachium (ulna and radius) are disarticulated, and the
two hands (manus) are turned out. It is very difficult to tell what is
going on at the base of the neck and body in that CM specimen because it is
obscured by being only half exposed (only one side faces us, the other is
still buried in the matrix) and the vertebrae at the base of the neck appear
kinked up. Furthermore, the zygapophyses appear to be very kinked together
and it is very difficult to make out what's going.
However, your point is well taken. We should always be skeptical of
computer models, especially when they do not appear to reflect what we see
in the bones. However, we should be careful about relying too heavily on
skeletons like the CM Camarasaurus as controls. After all, would we
conclude that the necks of Ornithomimid dinosaurs allowed them to swing
their heads upside down over their backs because we find some in this death
I would venture to politely disagree with you regarding the articulation of
disarticulated bones as controls. From my own experience, skeletons trapped
in rock or mounted present only one hypothesis or control of how the
skeleton could have gone together. By physically articulating dino bones in
a number of positions, we can sometimes find limits or motions that we would
not have guessed possible either from viewing skeletons in rock or those
mounted, and as such open up new hypotheses and ideas of what the limits to
The beauty of computer modeling dinosaurs, if done as accurately as possible
(and considering all the limitations we have with fossil material), is that
we can articulate together sauropods and other heavy beasts without
forklifts and prayers. DinoMorph is only capabale at this point of modeling
vertebrae, so most of my dissertation was a body building class: forklifts
and prayers. =) Can't wait to model those limbs in "virtual space" (but in
cyberspace I could use my sauropods to do battle with Gibson's cyberpunks.
Bring 'em on, Betty!). =)
In any case, Dr. Holtz has brought up some excellent, skeptical
considerations of the Parrish/Stevens model -- this is always welcome. The
only way we make any progress in science is to continually refine our
techniques and continually question our results. Each day, with any luck,
we get a little closer to reality.
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