Paleontologists have examined two exceptional specimens of a duck-billed dinosaur from the late Cretaceous period. Edmontosaurus annextens. Using a range of imaging techniques, they reconstructed the species' appearance in life, from the high crest on the neck and torso to the row of spines on the tail and hooves covering the toes; combined with fossilized traces, appearance Edmontosaurus annextens now at hand.
“This is the first time we've had a complete, detailed picture of a large dinosaur that we can really be confident about,” the University of Chicago professor said. Professor Paul Serenolead author of the study.
“The Wyoming Badlands where the finds were made is a unique ‘mummy zone’ that holds even more surprises from fossils collected over years of visits by teams of university students.”
Using historical photographs and fieldwork, Professor Sereno and his colleagues relocated sites in east-central Wyoming where several famous dinosaur “mummies” were discovered in the early 20th century, delineating a compact “mummy zone.”
They unearthed two new “mummies” in the folded river sand. Edmontosaurus annextens – in young and adult individuals – with large continuous areas of preserved outer surface of the skin.
Working with these specimens, they reconstructed the species' full, fleshy profile.
“The two samples complemented each other perfectly,” said Professor Sereno.
“For the first time, we were able to see the entire profile rather than individual sections.”
Paleontologists identified a continuous median line that began as a fleshy ridge along the neck and torso and passed through the hips into a single row of spines running down the tail—each spine located above one vertebra and adjacent to each other.
The lower body and tail had the largest polygonal scales, although most were tiny pebble-like scales, only 1–4 mm across, surprisingly small for a dinosaur that grew to over 12 m (40 ft) in length.
Wrinkles preserved on the chest suggest that the skin of this platypus was thin.
The hind legs of the larger “mummy” contained the biggest surprise: hooves.
The tips of each of the three hind toes were enclosed in a wedge-shaped hoof with a flat bottom, like a horse's.
The researchers used CT scans of the individual's feet and 3D images of the best-preserved duckbill print from the same time period, combining the former with the latter.
Using information from both sources, they accurately reconstructed the appearance of the hindfoot.
Unlike the forefoot, which only touches the ground with the hooves, the hind feet have a fleshy heel pad behind the hooves.
“These duck-billed 'mummies' preserve so many amazing 'firsts' – the earliest hooves recorded in a land vertebrate, the first confirmed ungulate reptile, and the first ungulate quadruped with different positions of the forelimbs and hindlimbs,” Professor Sereno said.
teams paper was published today in the magazine Science.
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Paul S. Sereno etc.. 2025. The fleshy midline and hooves of a duck-billed dinosaur demonstrate the “mummification” of an terrestrial clay template. Sciencepublished online October 23, 2025; doi: 10.1126/science.adw3536
