The mummified dinosaur skin preserved the bite marks of carnivores, likely ancient crocodiles.

The skin of a 67-million-year-old dinosaur has revealed bites and gashes from an ancient crocodile, and how its flesh was ripped apart may explain why it became mummified.

Skin decays much more easily than bone so it’s extremely rare to find fossilized dinosaur skin.

New research on a 7-meter (23-foot) long Edmontosaurus, a type of plant-eating hadrosaur, found near the town of Marmarth, North Dakota, in 1999 has shed light on what factors allowed the skin to survive through the eons.

“The bite marks were really unexpected. It had been thought that soft tissue wouldn’t preserve if it was damaged prior to burial, so the carnivore damage is what really started us thinking about how these fossils form in the first place,” said Stephanie Drumheller-Horton, a paleontologist at the The University of Tennessee’s department of Earth and planetary sciences, a coauthor of the new study.