RE: Death poses

["Matthew Bonnan" <mbonnan@hotmail.com>]

Julia:

The necks-kinked-back pose is due to "de-watering" of the nuchal ligament 
and muscles of the neck.  You can think of the nuchal ligament as a 
rubberband-like structure that runs from the base of the neck to the back of 
the skull.  When an animal lowers its head, the nuchal ligament is stretched 
like a rubber band and stores elastic energy.  When the animal relaxes its 
neck lowering muscles, the nuchal ligament "bounces" back, helping the 
animal raise its head without as much muscular effot -- it also helps an 
animal keep its head raised while walking without neck muscles expending a 
lot of energy to keep the head up.

We have a nuchal ligament, but it is very poorly developed.  Horses, cows, 
and many other such mammals have a large nuchal ligament.  When these 
animals die, their nuchal ligaments begin to dry out and shrink, pulling the 
head and neck back in a death pose.  The same sort of thing was likely going 
on in dinosaurs we find this way.  Because we find dinosaurs in this neck 
back death pose that were not in saline environments (like the 
aforementioned Camarasaurus lentus at CMNH by Christine Mills), the salinity 
of the enivironment is not what was causing this to occur.

Hope this helps,

Matt

Matthew F. Bonnan, Ph.D.
Department of Biological Sciences
Western Illinois University
Macomb, IL 61455
(309) 298-2155
mbonnan@hotmail.com
MF-Bonnan@wiu.edu

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