Many dinosaur fossils show the animals with neck arched backward. This appearance is so common, it has been dubbed the “dinosaur death pose.” Various theories have been invoked to explain it: dessication and final death throes among the most common. A study with chickens shows the arching neck is the automatic response of immersion in water.
Science Daily reported that scientists in Switzerland and Germany have re-evaluated the evidence for the so-called “opisthotonic” posture of these fossils. They found it hard to believe that these land animals were transported long distances from land to oceans. They ran experiments on chickens:
Convinced that the back arching was generated, not by death throes, but by postmortem alterations of a decaying carcass, the researchers made experiments with plucked chicken necks and thoraxes, immersed in water. Submersed in water, the necks spontaneously arched backwards for more than 90°. Ongoing decay for some months even increased the degree of the pose. Thorough preparation and dissection combined with testing revealed that a special ligament connecting the vertebrae at their upper side was responsible for the recurved necks in the chickens. This ligament, the so-called Ligamentum elasticum, is pre-stressed in living chickens, but also in dead ones.…
“A strong Ligamentum elasticum was essential for all long necked dinosaurs with a long tail. The preloaded ligament helped them saving energy in their terrestrial mode of life. Following their death, at which they were immersed in water, the stored energy along the vertebra was strong enough to arch back the spine, increasingly so as more and more muscles and other soft parts were decaying” conclude the researchers.
The classic Compsognathus fossil from Germany illustrates the pattern. “Therefore, biomechanics is ruling the postmortem weird posture of a carcass in a watery grave, not death throes.”
See comments from the 11/23/2011 entry.