Study reveals mummified dinosaur skin was bitten by ancient crocodiles

(CNN) – The skin of a 67-million-year-old dinosaur has revealed bites and cuts from an ancient crocodile, and how his flesh was torn may explain why he was mummified.

Skin breaks down much more easily than bone, so it is extremely rare to find skin from fossilized dinosaur.

New research on a 7-meter-long Edmontosaurus, a type of herbivorous hadrosaur, found near the town of Marmarth, North Dakota, in 1999, has shed light on the factors that allowed skin to survive through the eons.

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“The bite marks were really unexpected. Soft tissue was thought not to be preserved if damaged prior to burial, so carnivore damage is what really did us think about how these fossils formed in the first place,” said Stephanie Drumheller-Horton, a paleontologist in the University of Tennessee’s department of Earth and planetary sciences, who co-authored the new study.

Paleontologists used to think that a dinosaur, or any prehistoric creature, needed to be buried extremely quickly to preserve soft tissue, but this was not the case for this poor hadrosaur.

The researchers think the bite marks on the hadrosaur’s arm came from an ancient relative of a crocodile, but they’re not sure what kind of animal clawed or gnashed at its tail, though it was probably larger. It is unclear if the injuries to his arm and tail were killed or if they were inflicted by scavengers after their death.

Nevertheless, it was the misfortune of the dinosaur that allowed its skin to be preservedDrumheller-Horton explained.

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“To try to put it in the least disgusting way possible, piercing the skin allowed gases and liquids associated with subsequent decomposition to escape. That left the skin cupped behind to dry. Naturally mummified skin like this can last for weeks or months, even in fairly humid environmentsand the longer it lasts, the more likely it is to get buried and fossilized,” he said.

The bluish color of the fossilized skin is not thought to reflect what it would have been like when the dinosaur was alive. However, a high iron content in the rocks during the fossilization process may have affected it.

While often depicted as gray-green, it is largely unknown what color most dinosaurs were. Studies on fossilized feathers of dinosaurs have revealed that some were surprisingly colorful.

An artist’s impression of how the dinosaur may have died. North Dakota Geological Survey

Hadrosaur skin, however, has provided much information about the size and scale patterns throughout the dinosaur’s bodyas well as the amount of muscle mass, based on the expansion of the skin in that area.

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“Skin breaks down much more easily than bone, so different and less frequently observed processes are needed to preserve the skin long enough to bury and fossilize itsaid research co-author Clint Boyd, a senior paleontologist with the North Dakota Geological Survey.

Said maybe there were fewer than 20 true dinosaur “mummies”with complete or nearly complete sets of remnants with soft tissue.

“To put it in context, I have found thousands of fossils in my career, but only one of those preserved skin impressions (an imprint of the skin, not the preserved skin itself) and I never found one that had the skin preservedBoyd said via email.

The research was published in the journal PLOS One on Wednesday.