Scientists have uncovered remarkably preserved Edmontosaurus annectens mummies in Wyoming, revealing hooves, a hidden crest, and detailed skin features through a process called clay templating. This 66-million-year-old discovery provides the most complete reconstruction of the duck-billed dinosaur's appearance. The findings, detailed in a new Science paper, highlight unique preservation in a local 'mummy zone.'
About 66 million years ago, Edmontosaurus annectens dinosaurs in what is now east-central Wyoming underwent a rare preservation process after death. Their bodies dried in the sun before flash floods buried them rapidly, allowing a microbial film to attract clay particles and form an ultra-thin coating—less than 1/100th of an inch thick—that captured skin details in three dimensions. This 'clay templating' left no original organic material but created a detailed template of the exterior.
Researchers from the University of Chicago, led by Paul Sereno, rediscovered this 'mummy zone' in the badlands using old photographs. They excavated two new mummies: a younger individual and an older one, both with large patches of preserved skin surface. Advanced techniques, including CT scans, X-ray spectroscopy, and 3D imaging, allowed the team to reconstruct the dinosaur's full profile.
The reconstruction shows a tall fleshy crest along the neck and torso, transitioning to a single row of spikes on the tail, aligned above vertebrae. The body featured small pebble-like scales, 1-4 millimeters across, and thin skin with fine wrinkles over the ribcage. Most strikingly, the hind feet had wedge-shaped hooves enclosing the three toes, similar to a horse's, with a fleshy heel pad behind them—the earliest known hooves in any land vertebrate.
"It's the first time we've had a complete, fleshed-out view of a large dinosaur that we can really feel confident about," said Sereno, professor of organismal biology and anatomy at the University of Chicago. He noted the site's potential for more discoveries, excavated by university teams over years.
The hind feet differed from the forefeet, which contacted the ground only via hooves, marking the first confirmed hooved reptile and a four-legged animal with distinct limb postures. "There are so many amazing 'firsts' preserved in these duck-billed mummies," Sereno added.
This work outlines a model for soft-tissue preservation, aiding future fossil studies, and includes new preparation methods and terminology for scale types.