Scientists Finally Know What This ‘Mummified’ Dinosaur Looked Like

A recent study suggests the unique geology of an area in Wyoming makes it a trove of unusually preserved fossils

Sara Hashemi | Daily Correspondent

October 30, 2025

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Researchers have unearthed two dinosaur “mummies” in Wyoming—and the fossils within shed light on what the duck-billed creatures would have looked like 66 million years ago.

The dinos are a pair of Edmontosaurus discovered in the early 2000s in an area of the state’s badlands where famous fossil mummies were found in the early 20th century. These new fossils from the “mummy zone” were analyzed in a paper—published in the journal Science on October 23—that details what the creatures looked like and how those attributes were preserved for tens of thousands of years.

“For the first time, I think that we’ve got Edmontosaurus’ look completely down,” Paul Sereno, a paleontologist at the University of Chicago and lead author of the paper, tells the New York Times’ Jack Tamisiea. “Based on our drawings, you can put it in a Hollywood movie and it’s going to be accurate head to toe.”

Sereno and a team of researchers used CT scans, 3D imaging, electron microscopy and X-ray spectroscopy to examine the fossils, offering an unprecedented picture of the duck-billed dinosaurs.

The fossils were preserved without any traces of skin, the analysis suggests. “We looked and we looked and we looked, we sampled and we tested, and we didn’t find any” remnants of soft tissue, Sereno tells Amanda Schupak at CNN. The organic matter had entirely decayed and washed away, but a thin layer of clay hardened by microbes was left behind, encasing the fossils in a mummy-like carapace.

That layer of clay—less than one-hundredth of an inch thick—preserved details of the creatures’ skin, spikes and hooves. This style of preservation has been observed in marine environments before, but scientists did not think it was possible on land, reports Adithi Ramakrishnan for the Associated Press.

By working with the two mummies, the researchers were also able to determine that Edmontosaurus could likely grow over 40 feet long, had a thin duck bill, and had a fleshy crest along its neck and trunk that turned into a row of spikes running down its tail.

The hooves were especially surprising, per a statement. “There are so many amazing ‘firsts’ preserved in these duck-billed mummies—the earliest hooves documented in a land vertebrate, the first confirmed hooved reptile, and the first hooved four-legged animal with different forelimb and hindlimb posture,” Sereno says.

The study also suggests that the unique geology of the area is what makes it such a treasure trove of mummified fossils. During the Cretaceous Period, when dinosaurs last roamed the Earth, the climate cycled between droughts and monsoons. The droughts killed off the duck-billed dinosaurs, Serano explains in a piece for the Conversation, while flash floods quickly buried the bodies in sediment.

Finding more mummied dinosaurs can help scientists better understand these creatures, and the researchers involved in the study are already on the hunt for more. “Every single time we find one, there’s such a treasure trove of information about these animals,” Stephanie Drumheller, a vertebrate paleontologist at the University of Tennessee, Knoxville, who wasn’t involved in the study, tells the Associated Press.

That “treasure trove” appears to have delighted the researchers, who write in the statement that “Combined with fossilized footprints, the appearance of a duck-billed dinosaur—long guessed at but never demonstrated in this detail—is now at hand.”

For Serano, it’s a chance to do science with a broad public appeal while answering longstanding questions about the enigmatic animals that once dominated Earth. “We’ve never been able to look at the appearance of a large prehistoric reptile like this,” he says in the statement. “And just in time for Halloween.”

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Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.