For the first time, scientists have uncovered a clear and complete picture of what a large dinosaur looked like in real life—thanks to two remarkably preserved “mummified” fossils.
In a new study published in Science, researchers from the University of Chicago and their international collaborators describe how the skin, spikes, and hooves of a duck-billed dinosaur, Edmontosaurus annectens, were preserved in incredible detail for more than 66 million years.
The fossils, found in eastern Wyoming, capture the fine textures of the dinosaur’s outer body—down to scales just millimeters wide and even the shape of its hooves.
The secret to this stunning preservation lies in a process called clay templating.
Senior author Paul Sereno, a professor of organismal biology and anatomy at the University of Chicago, explained that when the dinosaur’s carcass was buried after a flash flood, a thin layer of clay—no thicker than a human hair—formed on its outer surface.
This clay mask acted like a natural mold, capturing the three-dimensional shape of the animal’s skin, crest, and even wrinkles.
The organic material later decayed, but the delicate clay film remained, preserving an exact imprint of the dinosaur’s exterior.
“It’s the first time we’ve had such a complete, fleshed-out view of a large dinosaur that we can really trust,” Sereno said. “These fossils give us the first confident glimpse of how this giant looked when it was alive.”
Using modern tools such as micro-CT scans, X-ray spectroscopy, and 3D surface imaging, the team examined the fossils layer by layer.
Fossil Lab manager Tyler Keillor led the painstaking process of exposing the fragile clay layer, which was so thin it could be blown away with a breath. Postdoctoral researcher Evan Saitta then used imaging data to reconstruct the dinosaur’s shape and match its hooves to fossilized footprints from the same site.
The result is the most lifelike reconstruction ever created of Edmontosaurus, a plant-eating dinosaur that lived during the final days of the Cretaceous Period.
The research also redefines what scientists mean by “dinosaur mummies.” These are not like Egyptian mummies containing preserved flesh; rather, they are fossils where a thin clay coating captured every surface detail of the skin before fossilization.
The fossils reveal that Edmontosaurus had a tall fleshy crest running along its neck and back, which continued into a row of spikes over its hips and tail. Each spike aligned neatly over a single vertebra.
Its body was covered with small, pebble-like scales—most only 1 to 4 millimeters across—making its skin surprisingly fine-textured for an animal that could grow more than 40 feet long.
Wrinkles preserved over the ribcage suggest that the skin was relatively thin and flexible.
But perhaps the most surprising discovery was on its feet: the first known hooves ever found in a reptile. CT scans showed that each of the three toes on the dinosaur’s hind feet was encased in a wedge-shaped hoof with a flat bottom—much like those of a horse.
These hooves would have provided stability and support for its massive body as it walked on soft ground. The team even fit the reconstructed feet perfectly into a fossilized footprint, confirming their findings.
“There are so many incredible firsts here,” Sereno said. “This is the earliest evidence of hooves in any land vertebrate—and the first time we’ve seen a reptile with hooves at all.”
Beyond revealing new details about dinosaur anatomy, the study also provides a framework for how similar fossils might form in the future.
The researchers outlined the steps of clay templating as a model for mummification—showing how sun-dried carcasses, flash floods, and electrostatic attraction between biofilms and clay minerals can together create a perfect natural mold.
The discovery also opens new directions for paleontology, from searching for other “mummy zones” in Wyoming and beyond, to building more accurate biomechanical models of how dinosaurs moved.
“This may be the single best paper I’ve ever released,” Sereno said. “It brings together fieldwork, lab science, and digital reconstruction to tell a full story—how these fossils formed, what they show us, and how they can change the way we see dinosaurs forever.”
Artwork created by artist Dani Navarro shows the newly reconstructed Edmontosaurus in vivid detail: a scaly, hoofed giant with a crest, spikes, and a powerful tail—walking across ancient river mud, just as it did 66 million years ago.
