[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Sauropod cervical vertebrae



Ah, the sticky question of sauropod necks.  I started on the tail end of 
these animals for more than one reason!  In sauropods necks come in all 
shapes and sizes with a varying number of cervical vertebral counts, from 
a low of ~12 to 17(?)+, however it must be pointed out that exact counts 
are often difficult due to a) complete cervical columns are pretty rare 
and b) telling a dorsal from a cervical vertebra can be _much_ more 
difficult than it would seem.  The most promising research being done on 
cervicals of sauropods is that of Kent Stevens and Mike Parrish, who are 
using computer modeling of zygapophysial articulations to determine the 
maximum amount of flexion permitted using zygs alone.  Their results were 
published in the previous 2 supplements to the JVP, with an accompanying 
poster in 1995 and a wonderful talk in 1996.  I have spent much time with 
Kent discussing zygs and their importance.  Euhelopus zdanskyi (George 
does improper internet spelling of genera and species go on my record?)  
had the most mobile neck while diplodocids couldn't get their necks must 
past horizontal, however the latter had great ventral flexion which would 
seemingly be great for munching in a tripodal position.  His 
Brachiosaurus model showed that, at best, the zygs allow a 45 degree 
angle, much less than its traditional "regal" appearance.  BUT it must be 
added that the cervical column of Brachiosaurus is not completely known 
(at least not with a complete set of articulated neural spines and zygs) 
and the cervico-dorsal transition area has been very difficult to work 
with.  That should all change within the next few years as discoveries in 
Wyoming and Colorado (the latter has been laying on the shelf for a 
number of years just begging to be published) have shed a whole new light 
on these 2 areas of Brachiosaurus.  (I almost hate writing sentences like 
the previous one...)  Until it does I will try to answer Wayne Anderson's 
very fine questions in numerical order: 
 1. Czerkas' claims seem to be somewhat born out for some taxa
 2. Other taxa (notably Euhelopus) could move their neck around so people 
have not necessarily "missed the boat"
 3. Any hotly raging debate regarding sauropod cervical vertebrae will 
have to leave me out until I have finished looking at all of the 
cervicals in the US (almost there, thankfully) and then abroad.  Until 
then I can offer up only what I can put your hands on.
 4. As I mentioned in the "preamble" some taxa seemingly could, others 
could not.
 5. I cannot speak for other paleontologists and their opinions of the 
Czerkas research, but for myself I critically evaluate his work as I 
would any others, and as I hope they will mine.  The fact that he does 
not have a PhD means nothing to me, its what he puts to pen that I can 
then go out and test that matters.  Others may disagree but I believe the 
publishing of ones ideas is rather frightening (and exhiliarting), as you 
are putting yourself "on the line".  I commend any who go through the 
often mindless tasks involved in publications (checking the format of the 
bibliography, all the same tense in a paragraph, captions all match the 
text, etc...) to put their ideas to print.  It is easy to simply 
"arm-wave" but when the words are written for all to see its hard to say, 
"well what I meant to say..."  
ok, off my soapbox and onto sauropods and Nick Longrich.
        I will have to check about Apatosaurus yahnapin and its upward 
bend at the base.  Any chance you can give me the citation?  I do not 
recall seeing it (the cervical character) in the Wyoming volume of last 
year, but I do know he has quite a bit of the beast.  You wrote 
"Brachiosaurs have an upward inclination to the spine, an upward bend at 
the bsae of the neck, and a nearly 90 degree angle between head and 
spine" then cited some semicircular canal work.  Any chance I can get the 
canal reference?  As for the upward inclination of the spine, I am not 
clear as to what you are referring to, if you want feel free to answer 
off line if it gets technical (that is unless the rest of you want to 
hear such "stodgy" info...).  I must admit I have never really thought 
about the skull's angle off the atlas/axis (though with only 1 skull of 
Diplodocus in positive articulation that makes for a pretty low sample 
size).  It is a really clever thought that I will explore further.  
        Lastly, Nathan Myhrvold wrote about the Mamenchisaurus ossified 
tendons and spoke of Alexander's work.  I have one burning question in my 
mind when I think of cranial dorsals:  WHY THE BLASTED BIFURCATION AND 
WHAT RAN DOWN THE TROUGH????  This question was asked at my thesis 
defense and absolutely frustrated me.  Why?  Well the medial borders of 
the bifurcate spines are SMOOTH!  Not rugose at all! The only rugosity 
in the neural spine region is at the base of the cleft.  I have spoken to 
a number of folks and none have given me a good answer as to what ran 
down the center.  Notice that humans have bifurcate cervical vertebrae 
(!  you can imagine my surprise when I dissected those babies out!)  
Nothing ran down their center (as weird as that sounds).  No one here in 
the anatomy department has any ideas they are willing to stand by, just 
guesswork.  One of the problems:  The bifurcation is deep and then fuses 
caudally, with the notch disappearing in the last dorsal of Diplodocus, 
but much more cranial in Apatosaurus (around number dorsal 6).  This is 
the bifurcate spine character I have seen George allude to in older 
posts, and it is one of the stickiest by far!  I am desperately seeking a 
functional answer to this question.  Brooks Britt argues they were filled 
with pneumatic cavities (hinted at in Britt (1993) and much personal 
communication (like at my defense, since he asked the question).  Some of 
these dorsal bifurcations are ridiculously deep (look at Janensch's (35/36?)
Dicraeosaurus and Amargasaurus cazuai from South America (the reference 
escapes me at the moment though if needed I can provide), these spines 
are exceedingly tall and fragile.  I talked my way through the question 
(it helps to know your committee members likes and dislikes) but have 
never arrived at a satisfactory conclusion.  
Regarding the heart dynamics and all of that physiology, I have 
absolutely no clue, I'll let the physiologists (or more probably take 
physiology) to figure it out...
        I love this forum atmosphere, I can throw things out that are on 
my mind!!!
        BC