Re: Ungulate-Type Nuchal Ligaments in Hadrosaurs? The Fossils Say No?

["Ralph W. Miller III" <gbabcock@best.com>]

"Jonathan R. Wagner" wrote:

>                Anyway, I found that, given nuchal ligaments supporting the 
> head in
>
> a resting pose as Paul shows, and assuming a feeding posture with the elbows
> bent, feeding nearly at ground level, any ungulate-like nuchal ligaments
> would have to stretch to nearly twice their length in order to allow such a
> range of movement.
>         Here I must admit my profound ignorance of the properties of
> ligaments. Does this sound reasonable to anyone?

See R. McNeill Alexander's _Dynamics of Dinosaurs & Other Extinct Creatures_.  
On
page 65 of the 1989 paperback edition, Alexander discusses the tension produced 
in
an extant deer's ligamentum nuchae when raised (1.4 times the slack length) and 
when
lowered as in drinking (2 times the slack length).  Thus, there is always 
tension on
the deer's nuchal ligament, and this causes the cut ligaments to snap like 
stretched
rubber bands during dissection.  The tension at maximum extension of the nuchal
ligaments of horses and cattle may be considerable, yet these animals have fully
functional necks.  If horses can extend their necks up and down with equal 
facility,
couldn't hadrosaurs have done the same?

Alexander discusses the hypothetical ligaments supporting sauropod necks and 
points
out that, without muscular support, the tension of holding a diplodocid neck 
nearly
horizontal would likely break the nuchal ligament.  Alexander suggests that 
muscles
took up some of the load (as in extant birds) and that an elastin (stretchy)
ligament seems feasible.  Do you suppose that the hadrosaurs could have likewise
incorporated elastin ligamentum nuchae?

-- Ralph W. Miller III       gbabcock@best.com

"Can do, can do.  This guy says the horse can do."