Dinosaur ‘mummies’ help scientists visualize the fleshy details of these ancient animals

The dinosaur “mummy” couldn’t be further from my mind as I raised a hay bale at Zerbst Ranch in east-central Wyoming, then on a field trip connected to my dinosaur science course for University of Chicago undergraduates.

As a university professor, I realized early on that in order to understand paleontology, students would need to see first-hand where fossils originate. And that field experience had to be real, a place I wanted to be — a place where we had a shot at discovery.

I chose the output of the Lance Formation, a rock formation consisting largely of sandstones that were laid down during the last few million years of the dinosaur era. These rocks are well exposed in Wyoming’s steep badlands, criss-crossed by dinosaur hunters for more than a century. Still, maybe they missed something.

Then I saw it.

At the top of the hill is a massive discord—a hard, iron-stained rock the size of a compact car—a few fossilized bone fragments. Poking out of it was a series of tiny stick-shaped bones that I recognized as the abdominal ribs of the giant predator Tyrannosaurus rex.

Raisins nearby

But T. Rex wasn’t alone in the surprising finds this field season. On the same field trip, colleagues working nearby discovered two fossilized duckbills—a plant-eating dinosaur that roamed in herds and grew to the length of a T-rex. They showed signs of extraordinary protection.

Sticking out from the vertical wall of the cutbank in the seasonally dry stream was a vertebra – part of the backbone – and some sharp tendons.

“What do you think?” asked my colleague Marcus Erickson, who counts paleontology, science education, and ecology among his other majors, along with paleontology. “You’ve got the back of a duckbill,” I said, referring to Edmontosaurus aniketans, the dinosaur’s official name likely to be on the T-rex’s dinner menu.

It would take Marcus two field seasons to remove more than 15 feet of rock from the skeleton. To his surprise, the tailbones were covered with large areas of exposed skin and topped with a row of spikes. When I visited the exposed skeleton and took a look at his foot, I noticed a hairline around the last bone of the toe. “Pull back, and take it,” I said, wide-eyed at what I saw. “I think it has hooves.”

Yet another group of bone hunters in the area found a Triceratops skeleton with a large slab of its skin exposed. Even finding a patch of skin on a skeleton. Exploring large areas of the outer fleshy surface of dinosaurs is the pursuit of a lifetime.

The mammification mystery

How is the skin of a dinosaur “mummy” preserved? What constitutes “skin impressions”?

Are these dinosaur “mummies” as preserved as human mummies from Egypt, where after someone dies, salt and oil are applied and then the skin, hair, internal organs and, as recently shown, their genome are used?

No. Dinosaur “mummies” do not preserve dehydrated skin. But many researchers believed that, perhaps, traces of tissue structures or even original organic material might remain.

To uncover dinosaur mammification, I needed my own skills and digital savvy. I recruited Ivan Sita to rigorously determine the composition of ancient open skin, after learning that he was cooking reptile skin to simulate fossilization.

I brought others on board: Dan Vidal, a Spanish paleontologist who was able to digitally capture surface detail in 3D. Nathan Mehrvold, a polyglot scientist after studying the chemistry of barbecue. Stephanie Baumgart, a paleontologist who stands in CT scans of living vertebrates. Maria Ciudad Real and Lauren Bopp, the first skilled in analyzing CT scans and later combining them into composite figures. Tyler Keller, who will invent new ways to clear old skin tissue. and Dani Navarro, a prolific Spanish paleontologist who reimagines prehistoric landscapes.

Mud mask, crusts, hooves and scales

We used diamond blades to section the skin, spikes, and hooves, and found that all were made of a very thin bound layer of clay—a clay mask or template—about an inch (less than 1 mm) thick. The sand on both sides of the clay layer was separate, indicating that when the body was buried, the same sand that pressed against the outside also entered the dry, hollow bodies through the many cracks and holes, filling all the internal spaces. Even the insides of the spikes and hooves were filled with sand.

We found no evidence of tissue structures within the clay layer, whether looking at open skin, spikes or hoofs. And we couldn’t find any trace of actual organic material. In other words, the original skin within the soil layer must have decomposed and washed away, while the same groundwater saturated the bones on their way to fossilization.

Our duckbill’s very realistic looking skin, spikes and hooves are actually a mask of clay, a thin layer applied to the outside that captures all the original shape and texture of the body surface.

To test the digital rendering we tested, we compared a digital version of a duckbill’s hoofed foot to a fossilized duckbill footprint on a museum shelf in Canada, discovered in beds of the same age as the Lens Formation. We adjusted our foot size a bit, to see if it was a snug fit. Together, the feet and footprints produced the first complete view of a duckbill’s fleshy foot.

The only duckbill currently alive is Edmontosaurus enchitenus, a possible track-maker. Its footprint was so well preserved that it showed scales on the sole of the foot.

The ‘Mummy’ Zone

The unique geology of the Lance Formation allowed many of these dinosaur mummies to be preserved in a small area, under the soil.

Natural gas and oil drilling in Wyoming has shown that the sandstone comprising the Lance Formation is deep beneath the rock mummies, measuring more than 1,000 meters (more than 3,200 ft). It is five times thicker than anywhere else in the west, suggesting that formations subsided more rapidly in the Mummy Zone, with periodic floods covering dry dinosaur carcasses.

During this late period of the dinosaur era in western North America, a monsoonal climate took hold. Severe drought brought death to vast herds of duck-billed dinosaurs—for some, right as they sought the last bit of water in dry riverbeds before succumbing. Then came the flash flood, bringing tons of sandy sediment that would cover the sun-dried dinosaur carcasses in an instant.

Only rarely do scientists get a chance to accurately imagine what any large dinosaur looked like when it was alive, because we usually have bones to reconstruct the beasts without a close analog. The dinosaur “mummy” offers us this extraordinary opportunity through the flow of conservation.

The dream research team I assembled was able to clean, scan, size, assemble, and otherwise restore duck-blooded dinosaur life exhibits from rare dinosaur mummies.

This article is reprinted from The Conversation under a Creative Commons license. Read the original article.