It may be easier for dinosaurs to “mummify” than scientists thought.

Unhealed bite marks on fossilized dinosaur skin suggest that: the animal’s carcass was captured before being covered with sedimentresearchers report October 12 in PLOS ONE. The finding challenges the traditional view that burial very soon after death is necessary for dinosaur “mummies” to form naturally.

The new research centers on Dakota, and Edmontosaurus fossil unearthed in North Dakota in 1999. About 67 million years ago, Dakota was an approximately 40-foot-long duck-billed dinosaur that ate plants. Today, Dakota’s fossilized limbs and tail still contain large areas of well-preserved, fossilized scaly skin, a striking example of dinosaur ‘mummification’.

The creature is not a real mummy because its skin has turned to stone, instead of being preserved as real skin. Researchers have come to call such fossils with beautifully preserved skin and other soft tissues mummies.

In 2018, paleontologist Clint Boyd of the North Dakota Geological Survey in Bismarck and colleagues embarked on a new phase of cleaning up and examining the dinosaur fossil. The team had what appeared to be tears in the tail skin and holes in the animal’s right front leg. To investigate what may have caused the skin spots, the researchers worked with Stephanie Drumheller, a paleontologist at the University of Tennessee at Knoxville, to remove extra rocky material around the spots.

The holes in the skin — especially those in the front limbs — match up well with bite marks from prehistoric relatives of modern crocodiles, the researchers say. “This is the first time this has been observed in dinosaur soft tissues,” Drumheller said.

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Because the markings on the tail are larger than those on the front limbs, the team thinks that at least two carnivores on the Edmontosaurus

carcass, probably as scavengers because the wounds didn’t heal. But cleaning up doesn’t fit the traditional view of mummification.

“This assumption of rapid burial has been ingrained in the explanation for mummies for a while,” Drumheller says. That was clearly not the case for Dakota. If scavengers had enough time to snack on his body, the deceased dinosaur would have been out in the open for a while.

Observing Dakota’s deflated skin sheath, shrink-wrapped to the underlying bone with no muscles or other organs, Drumheller had an unexpected “eureka moment,” she says. “I had seen something like this before. It just wasn’t in the paleontological literature. It was in the forensic literature.”

When some smaller modern scavengers such as raccoons feed on the internal organs of a larger carcass, the scavengers tear open the body of the carcass. The forensics found that this hole gives any gases and liquids from further decomposition an escape route, allowing the remaining skin to dry out. Funeral can take place afterwards.

The researchers “have a very good point,” said Raymond Rogers, a researcher at Macalester College in Saint Paul, Minn., who studies how organisms decay and solidify, and was not involved in the study. “It would be highly unlikely for a carcass to reach advanced stages of dehydration and also experience rapid burial. These two commonly assumed conditions for mummification seem somewhat incompatible.”

Fossilization of soft tissues — such as skin or brain or fleshy head ridges — is uncommon, but not unheard of (SN: 20-8-21; SN: 12/12/13). “If [soft tissue] requires a spectacular confluence of strange events to solidify it, it’s much more common than you’d expect if it were,” Drumheller says. Perhaps mummies that come from the ordinary fate of carcass can explain this.

But while dry, “chapped” skin could survive long enough to be buried, the conditions involved aren’t necessarily common, says Evan Thomas Saitta, a paleontologist at the University of Chicago who was not involved in the study.

“I still suspect that this actual process is a very precise sequence of events, where if you get the timing wrong, you’ll run out of a mummy dinosaur,” he says.

To understand that sequence of events, and how common it is, you need to figure out how fossilization proceeds after a mummy’s burial. This is an area of ​​research Boyd says he wants to explore.

“Is it just the same process of fossilization as for the bones?” he asks. “Or do we also need a different set of geochemical conditions to then fossilize the skin?”