October 23, 2025
3 min learn
Fossilized Pores and skin on Dinosaur ‘Mummies’ Isn’t Pores and skin at All
Wyoming’s “dinosaur mummies,” as soon as thought to protect fossilized flesh, are literally detailed clay molds shaped by microbes because the creatures decayed
Mummy of the juvenile duck-billed dinosaur Edmontosaurus annectens preserved as a dried carcass resting on its ribcage some 66 million years in the past. Giant areas of scaly, wrinkled pores and skin and a tall fleshy crest over its again have been preserved as in a skinny layer of clay over its fossilized skeleton.
Greater than a century in the past prolific fossil collector Charles Sternberg found the skeleton of a duck-billed Edmontosaurus dinosaur within the sandstone rocks of the Lance Formation in japanese Wyoming. The stays have been lined in fossilized flesh and pores and skin, making it the primary “dinosaur mummy” ever discovered. Two years later Sternberg would discover one other one only a few kilometers away.
New analysis reveals, nonetheless, that the pores and skin discovered on newly found duck-billed dinosaur “mummies” from the identical space—and possibly Sternberg’s as properly—aren’t fossilized flesh in any respect however clay molds welded by microbes because the creatures decayed.
“That’s going to return as a shocker to lots of people,” says College of Chicago paleontologist Paul Sereno, lead writer of the brand new research, printed in Science. This clay molding course of was identified to protect the type of comfortable animals in oxygen-poor areas, such because the muds on the backside of lagoons and deep-sea trenches, Sereno says. However “nobody imagined it may work its magic on a dinosaur buried abruptly by sand in a flooded river,” an atmosphere that’s pretty oxygen-rich.
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The scaly pores and skin of a crest over the again of the juvenile duck-billed dinosaur Edmontosaurus annectens, nicknamed “Ed Jr.” The juvenile duckbill, estimated to be about two years outdated on the time it died, is the one juvenile dinosaur mummy ever found.
When “mummified” on this means, all of an animal’s outdoors comfortable tissues grow to be movies of clay lower than 1 millimeter thick. Sereno proposes that the creatures’ carcasses have been first desiccated in a drought earlier than abruptly being engulfed by sediment—possible introduced on by a flood. A layer of micro organism latched onto the moist, porous floor to kind a biofilm, which attracted surrounding clay. Then, weeks after they have been buried, the comfortable components of the carcasses decayed and have been washed away by groundwater, leaving the clay masks to perpetually protect the types of what lay simply beneath, Sereno says.
“The type of primary [fossilization] query of ‘How did this factor fossilize within the first place?’ hasn’t obtained as a lot consideration prior to now,” says Stephanie Drumheller, a paleontologist on the College of Tennessee, Knoxville, who was not concerned within the research however is talked about in its acknowledgments part. “I feel this was a very nice deep dive into this one space the place we do see a number of specimens.”
Three sexy spikes are preserved on atop of the tail of a mummy of an grownup duck-billed dinosaur Edmontosaurus annectens nicknamed ‘Ed Sr.”.
Sereno and different researchers have managed to uncover many extra mummies close to Sternberg’s authentic Wyoming web site. These have included a Triceratops horridus and a Tyrannosaurus rex, together with two extra E. annectens that have been described for the primary time within the new research. All are inside a 10-kilometer diameter of each other in an space Sereno calls the “mummy zone.”
One in all these E. annectens was two years outdated when it died and the opposite 5 to eight years outdated—making them a “late juvenile” and “early grownup” that the researchers named “Ed, Jr.” and “Ed, Sr.,” respectively. Ed, Jr., the “late juvenile,” is the primary adolescent dinosaur mummy ever discovered and the primary giant dinosaur with a totally preserved fleshy define of its trunk. In the meantime Ed, Sr., the “early grownup,” is the primary dinosaur of its variety to have been discovered with a full set of spikes working alongside its tail, and it has the earliest identified hooves of any four-footed animal.
The hoof, preserved in part as a really skinny clay layer, caps the top toe bone within the foot of an grownup mummy of the grownup duck-billed dinosaur Edmontosaurus annectens.
The researchers used a sequence of strategies involving x-rays, CT scans, and microscopic and chemical analyses to make sure that the fleshy components have been certainly only a clay molding. This course of is painstaking, and the clay on many earlier specimens has been inadvertently broken or eliminated throughout preparation.
“They have been coming at this query from a whole lot of completely different angles,” Drumheller says, “to determine what the historical past of this fossil was, how this factor grew to become a fossil within the first place—after which tying that in to the bizarre situations that appear to have been round on this atmosphere the place they’ve discovered so many mummy fossils.”
“The query now earlier than us,” Sereno says, “is whether or not this clay masks preservation course of applies to the opposite dinosaur mummies and pores and skin renderings which were discovered at many different websites around the globe.”
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