Fossilization happens when minerals gradually replace bone in an animal that is buried underground. Mummification happens when a body's soft tissue dries completely out and is preserved by desiccation. A few mummified remains of dinosaurs have been found with evidence that the dead animal was quickly buried in dry conditions, such as in an avalanche. But an Edmontosaurus found in South Dakota in 1999 defied all explanation. The 40-foot-long reptile died 67 million years ago, but its bones were found covered by fossilized skin! That could have only happened if the sky were dried out, as in mummification, before it was fossilized. But this dinosaur died in wet conditions, and was not immediately buried. In fact, there is evidence that it laid on the earth's surface long enough for other animals to take a few bites out of him. How could its skin have have been preserved at all?
A new theory about the Edmontosaurus nicknamed Dakota was published this week. Scientists now believe that scavengers helped the drying process. By tearing the skin open, they allowed for the blood, gasses, body fluids, and internal organs to ooze out before putrefaction, which sped up the ability of the skin to dry out. The precise sequence of events that led to Dakota turning to just skin and bones before being buried and fossilized has to be a pretty rare event, but one that gave us dinosaur skin to study 67 million years later.
(Image credit: Natee Puttapipat)