When paleontologists unearth a dinosaur, they’re usually digging up bones from its skeleton. In rare cases, though, the animal’s soft tissues, such as skin, are also intact. Scientists had thought these “mummified” fossils could only form if the organism was buried quickly after death or preserved by dry surroundings. But new research suggests another way that a dinosaur mummy could be created.
“There used to be an assumption that, in order to get a mummy, you absolutely had to have rapid burial,” Stephanie Drumheller-Horton, lead author of the new paper and a paleontologist at the University of Tennessee, Knoxville, tells Live Science’s Nicoletta Lanese.
Now, scientists have been studying the fossilized remains of a duck-billed dinosaur that appears to have done the opposite—it died in a wet place and lay out in the open for some time. Still, the specimen’s limbs and tail are covered with large areas of preserved skin, writes the New York Times’ Jeanne Timmons.
In the paper, published Wednesday in the journal PLOS ONE, the researchers hypothesize that scavenger activity while the dinosaur’s body was still exposed might have actually helped save the skin. The findings suggest there might be more well-preserved dinosaur soft tissues buried in the ground than scientists previously thought, according to Live Science.
The idea that scavenging might have contributed to mummifying skin is “an exciting discovery,” Fion Waisum Ma, a vertebrate paleontologist at the Smithsonian’s National Museum of Natural History who did not contribute to the paper, tells the Times. “This study is comprehensive,” she said, “and gives us a new perspective on how soft tissue preservation may have occurred in dinosaurs and more generally in land vertebrates.”
The well-preserved remains come from an Edmontosaurus specimen nicknamed Dakota, which was unearthed on a ranch in southwestern North Dakota in 1999. The duck-billed herbivore lived about 67 million years ago and was nearly 40 feet long. Though Dakota “isn’t a true mummy because its skin has turned into rock,” researchers still use the term, writes Science News’ Jake Buehler.
“The skin itself is a very deep brown, almost brownish black, and it actually has a bit of a shine to it because it has so much of that iron in it,” from the fossilization process, Mindy Householder, a co-author of the paper and a fossil preparator for the State Historical Society of North Dakota, says to Live Science. “It almost looks like it’s glittering.”
Dakota’s skin has bite marks on it that indicate the animal's remains were scavenged by multiple types of carnivores—perhaps ancient crocodiles or other dinosaurs—suggesting the body was out in the open for a while.
Still, Drumheller-Horton hadn’t figured out how the skin was so well-preserved. But then she realized that Dakota’s deflated skin reminded her of something she’d seen in the forensic literature: mummified remains of humans and mammals, she tells Science News.
“This is weird and unexpected if you’ve only read the paleontological literature dealing with mummies,” Drumheller-Horton tells the Times. “But it’s really in line with the forensic anthropological literature.”
Scavenging of human and mammalian remains can create pathways through which liquids and gasses can escape the corpse, enabling the skin to dry out and become preserved, per the Times.
“Instead of all of that stuff sticking around inside the body, keeping it wet, pushing that decomposition along, it’s now out of the way,” Drumheller-Horton says to New Scientist’s Christa Lesté-Lasserre. “It’s basically hollowed out and able to dry out, and what you have left behind is skin and bones.”
The new paper makes a “strong case” that Dakota was out in the open for a while before burial, Karen Poole, a paleontologist at the New York Institute of Technology who was not involved in the study, says to National Geographic’s Riley Black.
Though the research reveals a new way for mummified dinosaurs to exist, such well-preserved skin still might not be too common, Evan Thomas Saitta, a paleontologist at the University of Chicago who did not contribute to the paper, tells Science News.
“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 tells the publication.