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Re: Vertebral spines on sauropods...



Brian Franczak wrote (12/11/98; 2:04p):

>The general consensus these days seems to favor spikes, but that idea 
always struck me as odd for the very reason inherent in my original 
question: I know
of nothing analogous in nature. Impossible for _Amargasaurus_ then? No,
of course not. But as an illustrator, I can't sit on the fence; I have
to make a decision one way or the other -- based on research and my own
intuition -- on how to interpret the fossil as I restore the animal.
Since I'm in the process of (finally!) working on a painting of
_Amargasaurus_, I was trying to bolster my own interpretation based on
what I though made sense. Or conversely, have it shot down with
sufficient evidence to support the contrary idea.<

and, quoting Tom Holtz:

>> I think what Brian (or Jaime?) was asking was whether the neural 
spines each
> emerged as a separate spike out of the fleshy part of the neck of
> _Amargasaurus_.  This is not known directly from the fossils, and is 
one of
> two commonly suggested model.  I can't think of any living animal in 
which
> we can demonstrate a neural spine forming an isolated spike.<


I am skeptical of that emerging general consensus.  I don't want to be 
guilty of favoring a just-so story (i.e., I don't have any real evidence, 
as you requested), but I think if the spines were sticking out 
individually, they might interfere and grate past each other when that 
relatively flexible neck was flexed in certain ways.  Remember the spines 
were rigidly fixed in place, and couldn't flap in the wind; this 
arrangement would have promoted "self injury".
  
Maybe the Amargasaurus neck seems like it might have been more flexible 
than that of certain other sauropods precisely because nothing other than 
neural spines TIED TOGETHER were necessary to keep the neck from flexing 
more than in other sauropods.  Two parallel "sails" reinforced with 
ligaments would not only help hold the neck up, but might also tend to 
keep it from flexing to the sides. 

Incidentally, I did not mean to sound quite so flippant in my earlier 
posting.  It would have sounded better over a beer.  My point was that it 
is OK to have unique animals, and the fossil record shows that others 
existed. (And here I do not mean to counter my own argument above.  
Unique animals, different from any living ones, yes; unique in THAT way, 
no).


*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu