It might be easier for dinosaurs to “mummify” than scientists thought.
Evidence suggests that fossilized dinosaur skin has unhealed bit marks. the animal’s carcass was scavenged before being covered in sedimentResearchers report October 12th in PLOS ONE. The finding challenges the traditional view that burial very soon after death is required for dinosaur “mummies” to naturally form.
Dakota is the new focus of research. EdmontosaurusNorth Dakota fossil discovered in 1999. Dakota was a duck-billed dinosaur approximately 12 meters long that consumed plants about 67 million years ago. 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 isn’t a true mummy because its skin has turned into rock, rather than being preserved as actual skin. Researchers now refer to fossils that have preserved their skin and other soft tissue as mummies.
Clint Boyd, North Dakota Geological Survey in Bismarck’s paleontologist, and his colleagues started a new phase of cleaning and examining the dinosaur fossil. The team had found what looked like tears in the tail skin and puncture holes on the animal’s right front foot. Stephanie Drumheller, a paleontologist from the University of Tennessee, Knoxville, was enlisted to investigate the cause of the skin scars.
The holes in the skin — particularly those on the front limb — are a close match for bite wounds from prehistoric relatives of modern-day crocodiles, the researchers say. “This is the first time that’s been seen in dinosaurian soft tissues,” Drumheller says.
The tail marks are bigger than the marks on the front limb so the team believes that at least two carnivores may have eaten the tail. Edmontosaurus carcass, probably as scavengers because the wounds didn’t heal. But scavenging doesn’t fit into the traditional view of mummification.
“This assumption of rapid burial has been baked into the explanation for mummies for a while,” Drumheller says. That clearly wasn’t the case for Dakota. The body of the dino could have been left out for a while if scavengers had had enough time to eat it.
Observing Dakota’s deflated skin envelope, shrink-wrapped to the underlying bone with no muscle 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 forensics literature.”
When some smaller modern scavengers like raccoons feed on the internal organs of a larger carcass, the scavengers rip open the carcass’s body. According to forensics research, this hole allows any gases or fluids from further decay an escape route. The skin can then dry out. After that, burial could occur.
The researchers “make a very good point,” says Raymond Rogers, a researcher at Macalester College in Saint Paul, Minn., who studies how organisms decay and fossilize and wasn’t involved in the research. “It would be very unlikely for a carcass to achieve advanced stages of desiccation and also experience rapid burial. These two generally presumed prerequisites for mummification seem to be somewhat incompatible.”
Fossilization of soft tissues — like skin or BrainsOder Skin-friendly head combs — is uncommon, but not unheard of (SN: 8/20/21; SN: 12/12/13). “If [soft tissue] requires some spectacular confluence of weird events to get it fossilized at all, it’s far more common than then you would expect if that was the case,” Drumheller says. Drumheller suggests that mummies made from common carcass fates might explain this phenomenon.
But while dry, “jerkylike” 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 with the study.
“I still suspect that this actual process is a very precise sequence of events, where if you get the timing wrong, you end up without a mummy dinosaur,” he says.
Understanding that sequence of events, and just how common it is, requires figuring out how fossilization proceeds after a mummy’s burial. This is an area of research that Boyd says he’s interested in looking into next.
“Is it just the same fossilization process as for the bones?” he asks. “Or do we also need a different set of geochemical conditions to then fossilize the skin?”
