Scientists working in Wyoming's badlands have uncovered two rare fossilized "mummies" of hoofed Edmontosaurus, a large duckbilled dinosaur. The finds preserve the animals' bodies with exceptional detail and reveal an unexpected feature: hooves. No dinosaur has ever been shown to possess hooves before.
Researchers examined the preserved skin and limb structure and found that Edmontosaurus had hoof-like coverings on its toes. This suggests the dinosaur was adapted for efficient movement over solid ground, perhaps even capable of running. The discovery rewrites a major part of dinosaur anatomy and locomotion.
The fossils date to about 66 million years ago, near the end of the Cretaceous Period. One individual was a young adult about 40 feet long. The second was a two-year-old juvenile around half that size. Their outer shapes survived thanks to a thin coating of clay that molded to the skin after death, capturing the animal's natural form.
University of Chicago paleontologist Paul Sereno said the fossils show the full outline of the dinosaur in life -- a rare achievement in paleontology. He explained that these "mummies" are not like Egyptian ones. No DNA or internal tissues remain. The clay simply formed a natural casing over the bodies, preserving the outer surface like a mask.
Edmontosaurus lived alongside Tyrannosaurus, Triceratops, and Ankylosaurus in western North America. Sereno described it as the most abundant dinosaur in its environment, filling a role similar to modern grazing animals. Bite marks on other remains show it was likely a frequent meal for T. rex.
Hooves evolved in mammals such as horses millions of years later. Edmontosaurus is now the earliest known land vertebrate to evolve them. The trait demonstrates convergent evolution -- unrelated animals developing similar features to survive in similar habitats.
The dinosaurs had a fleshy midline crest that turned into a row of tail spikes. Their skin bore fine pebble-like scales like those of a lizard. Scientists think both animals died in a drought. A sudden flash flood later buried them under clay, preserving their bodies with extraordinary clarity.
Researchers relocated the early 20th-century "mummy zone" using historical photos. New digs there uncovered more fossils, including Tyrannosaurus and Triceratops. One Tyrannosaurus fossil showed a skin surface without scales, suggesting it may have been feathered.