Researchers now have a new idea of what a certain type of duck-billed dinosaur looked like, thanks to experts from the University of Chicago who uncovered dinosaur mummies.

In a new paper published in the journal Science, the experts describe how 66 million years ago, carcasses of the dinosaur Edmontosaurus annectens were transformed into "mummies" that preserved fine details of their scales and hooves, the University of Chicago said.

In a process called clay templating, the skin and soft tissues of the dinosaur are preserved over the skeleton after burial by a clay mask of a thickness of no more than 0.01 inch, the university said.

Several such specimens — dinosaur mummies — were found in the early 20th century in east-central Wyoming, the university said. For this new research effort, renowned U of C paleontologist Paul Sereno and his team returned to that same area, where they mapped out a "mummy zone" at the southern edge of the flat-lying Hell Creek and Lance rock formations near the Cheyenne River.

In the mummy zone, Sereno found two new Edmontosaurus mummies — one an older juvenile, the other a younger adult. Both had large continuous areas of tissue impressions that thin clay mask.

Sereno emphasized in a UChicago news release that dinosaur mummies are not like the human mummies in Egyptian tombs, which still have organic matter preserved. No actual tissue from the Edmontosaurus specimens is left — their hooves, skin, and spikes are only preserved in the form of that thin clay film.

"This is a mask, a template, a clay layer so thin you could blow it away," Sereno said in the release. "It was attracted to the outside of the carcass in a fluke event of preservation."

The experts went on to use imaging tools such as hospital and micro-CT scans, thin sections, and X-ray spectroscopy, which led them to figure out how the dinosaur mummies' impressions had been preserved in such a fashion with clay in the ground.

What happened was that the dinosaurs' corpses were lying out in the sun, only to be suddenly buried in a flash flood. A biofilm on the carcasses electrostatically pulled clay out of the sediment, and the clay congealed to a wafer-thin layer that preserved the dinosaur's form three-dimensionally, the U of C said.

The clay went on to harden with the help of microbes. Meanwhile, the organic material decayed away, while the skeleton under the clay film fossilized over a longer timescale, the university said.

In examining the dinosaur mummies, the UChicago scientists were able to develop a clearer picture of what the duck-billed dinosaurs looked like when they were alive.

They learned that Edmontosaurus had a midline feature that began as a fleshy crest on its neck and trunk and ended as a row of spikes along its tail — with each spike positioned over a vertebra.

The scientists were also able to determine that Edmontosaurus had small scales for a dinosaur that could grow to 40 feet, and that Edmontosaurus had hooves with a flat bottom like those of a horse — which was the biggest surprise, the university said. This makes Edmontosaurus the first confirmed hooved reptile, and the bearer of the earliest hooves documented in a land vertebrate, Sereno said in the release.

The team also brought in digital artists, who depicted the dinosaur walking in the mud toward the end of the dinosaur era, the university said.

"I believe it's worth taking the time to assemble a dream team in order to generate science that can be appreciated by the general public," Sereno said in the release. "We've never been able to look at the appearance of a large prehistoric reptile like this—and just in time for Halloween."

Sereno, who has discovered numerous new dinosaur species and has been a celebrity dinosaur hunter for many years, said the paper on the dinosaur mummies discovery may be the single best paper he has ever released.

Among the co-authors of the paper was Tyler Keillor, the manager of Sereno's fossil lab, whose accomplishments as a paleoartist warranted a "Someone You Should Know" feature piece by the late CBS Chicago anchorman and reporter Harry Porterfield back in 2011.