"Somewhere, something incredible is waiting to be known" Carl Sagan
sábado, 26 de noviembre de 2011
Palaeontology - Watery secret of the dinosaur death pose
Recreating the spectacular pose many dinosaurs adopted in death might involve following the simplest of instructions: just add water.
Dinosaur death pose [Credit: arcticwoman/Flickr]
When palaeontologists are lucky enough to find a complete dinosaur skeleton – whether it be a tiny Sinosauropteryx or an enormous Apatosaurus – there's a good chance it will be found with its head thrown backwards and its tail arched upwards – technically known as the opisthotonic death pose. No one is entirely sure why this posture is so common, but Alicia Cutler and colleagues from Brigham Young University in Provo, Utah, think it all comes down to a dip in the wet stuff.
Cutler placed plucked chickens – both fresh and frozen – on a bed of sand for three months to see if desiccation would lead to muscle contractions that pulled the neck upwards – a previously suggested explanation for the death pose. The chickens decayed without contorting. When seven other chickens were placed into cool, fresh water, however, their necks arched and their heads were thrown back within seconds. Sustained immersion of the birds for up to a month slightly increased the severity of the pose, but the major movement of the head occurred almost immediately.
The result contrasts with a study carried out in 2007 by Cynthia Marshall Faux at the Museum of the Rockies in Bozeman, Montana, and Kevin Padian at the University of California in Berkeley. The pair found that salty water did not alter the pose of dead quails. They concluded that the arched back seen in so many fossils was instead the result of the expiring dinosaur's final death throes (Paleobiology, DOI: 10.1666/06015.1) – an idea that was first suggested by pathologist Roy Moodie in 1918.
Why dunking dead birds in water produced different results in the two studies is not clear. It's possible that the salt content of the water was a factor – but Cutler has confidence in her freshwater study: "Although the roads to the opisthotonic death pose are many, immersion in water is the simplest explanation."