Re: DinoMorph Strikes Back!... or does it?

["Kent A. Stevens" <kent@cs.uoregon.edu>]

A few comments regarding Gregory S. Paul's (GSP's) communication:

1) I agree with GSP regarding:  [for all sauropods to have low-slung  
necks] "... it's not impossible, but it's really odd".  Sauropods  
were probably very odd indeed, and not fitting nicely into some  
preconceived notions.  Specifically, for such large terrestrial  
vertebrates to have such long necks and not go around holding them  
nearly vertically, giraffe-like ...  I can see how that would rub  
some people the wrong way.

2) For those unfamiliar with the juvenile _Camarasaurus_ CM 11338  
from personal observation, I have posted some pictures that clearly  
show how the neck is preserved in a hyper-dorsiflexed pose.  The  
zygapophyses are clearly disarticulated at most intervertebral  
joints.  This fact should not be a matter of argument or artistic  
disagreement.  The postzygapophyses are translated caudally as a  
consequence of dorsiflexion to the point they are physically wedged  
tight against the ascending neural arches of the more caudal  
cervical.   For those of you that have only seen photographs (or  
drawings) of this specimen in lateral view, the photographs should be  
informative and settle any doubts that might remain as to whether  
this juvenile is preserved in a comfortably achievable happy-young- 
sauropod-out-for-a-stroll posture.

You may find the newly introduced images by selecting Camarasaurus  
(from the second menu from the left) on the following site:

http://www.cs.uoregon.edu/~kent/DinoMorph

then scrolling to the bottom and clicking the link to CM 11338

or just look directly at them here:

http://www.cs.uoregon.edu/~kent/DinoMorph/Camarasaurus/CMNH11338.html

3) Regarding the remarkable _Camarasaurus_ specimen with two fused  
vertebrae (AMNH 5761/X-a-5-605).  Just look at them.  They sure seem  
to be in collinear alignment when you are right there in the big bone  
room at the AMNH looking at them.  The pictures kindly taken by Rick  
Edwards and facilitated by Carl Mehling convey much of the story.   
Here are shortcuts to the images:

http://www.cs.uoregon.edu/~kent/DinoMorph/Camarasaurus/images/AMNH/ 
5761a-02.jpg
http://www.cs.uoregon.edu/~kent/DinoMorph/Camarasaurus/images/AMNH/ 
5761a-03.jpg

4) In the 1999 Science article Mike Parrish and I published, the  
manuscript originally included data for 25% and 75% overlap as well  
as the 50% overlap, but the other estimates were dropped in the  
editing in order to save column inches.  But curiously the height  
results for 25% safety factor were rather similar to those for 50%,  
for reasons that seem to escape GSP:  to raise the head (and NOT  
merely curl the neck into an arc), almost all the dorsiflexion must  
arise at the base of the neck.  The mid neck, and especially the  
cranial few cervical vertebrae must remain STRAIGHT in order to  
maximize the elevation of the head.  So the large number of cervical  
vertebrae don't really enter into how high the head can raise. One  
cannot trivially multiply (say) 5 degrees per joint times 18 joints  
(= 90 degrees) and conclude the neck forms a right angle with respect  
to the trunk of the animal.  What would result is an arc of  
diminishing radius of curvature (because centra length diminishes  
cranially).  Such simple numerology does not yield the desired  
giraffe-like neck, the kind with a sharp kink at the bottom and a  
derrick-like ascent. To get a giraffe-like neck requires specialized  
vertebral morphology at the base of the neck, which informally we  
call "wedge-shaped" or "keystone shaped".  Incidentally, some  
dinosaur illustrations (particularly of camarasaurids and  
brachiosaurids) show both a sharp upturn at the base AND an  
inflection point at mid neck (i.e. an overall sigmoid or reflex  
curve).  In order to create a reflex curve, the cranial portion of  
the neck must be ventriflexed and the caudal part dorsiflexed (if  
they are not already so-disposed in their osteologically neutral  
pose, as in the horse, and the avian neck, for instance).  Trying to  
put a swan-like sigmoid curve in a sauropod neck, one ends up with a  
disappointingly low-amplitude sigmoid curve (unless, of course, one  
disarticulates the vertebrae where necessary to create the desired  
curve).

5) Sorry, but I must reiterate that when compositing original  
published illustrations to reconstruct a vertebral series, one needs  
to be mindful of the fact that 1) the vertebrae are sometimes not  
depicted in correct scale within the original document, and 2) some  
bones are crushed and significantly distorted diagenetically.  The  
first issue induces artifactual curvature, leading to the false  
impression of a truffle-hunting, or gopher-hunting sauropod in  
osteologically neutral position.  I hope this red herring doesn't  
keep rearing its ugly head, to mix metaphors.  The second issue,  
attempting to place a distorted vertebrae into close articulation  
with its adjacent vertebrae, is simply silly.  For that reason, I pay  
careful attention to the image scale of each vertebra image, and  
secondly, place any distorted elements with caution, using the  
adjacent vertebrae as an overall guide  (such as I did regarding the  
noted sixth caudal of _Apatosaurus_ CM 3018 from Gilmore, some  
_Dicraeosaurus_ presacrals, and the mid-cervicals of _Diplodocus_ CM  
84 that cause a downturn which Mike Parrish and I checked by  
manipulating casts of the originals, and concluded is due to  
distortion).  The photo-composites, therefore, indeed leave some gaps  
where frank distortions arise in the component vertebrae, so that the  
educated eye can clearly see the distortion for what it is.

BOTTOM LINE:  the osteological adaptations used by extant vertebrates  
to induce neck curvature, and specifically to elevate the neck, are  
absent in all the sauropod specimens we have thus far examined.  Find  
us some wedgies, and we'll be delighted.  Otherwise, the sauropods  
all seemed "odd" indeed:  long necks hanging way out in front, about  
horizontally, maybe a droopy like that of "Eeyore" (reconstructed so  
artistically, and yet accurately, by E.H. Shepard for A.A. Milne's  
Winnie the Pooh).