Re: "Split" neural spines on archosaur vertebrae

[Phil Bigelow <bigelowp@juno.com>]

On Fri, 17 Jun 2005 02:11:28 -0700 Mickey Mortimer
<Mickey_Mortimer111@msn.com> writes:
> Phil Bigelow wrote-
> 
> > The posterior ends of the neural spines of some archosaur 
> vertebrae are
> > "split", as though someone had taken a knife and made a cut.  What 
> is the
> > function of the split?  What groups have this character?


> This is the interspinous ligament groove, right?  Which I assume is 
> named
> such because ligaments which span the space between neural spines 
> (and/or
> alongside them?) attach there.


Yes, that name rings a bell.
The groove isn't found in all taxa (in some taxa, the ligaments simply
pass along the sides of the neural spines).  Is the presence or absence
of the ILG used in character trait matrices?

If I had to guess, I would say that the groove is a derived character for
vertebrates in general?  Would having the ligaments passing over the top
of the neural spine (rather than along the sides of the spine) make the
vertebral column more flexible or less flexible?

<pb>
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