Edmontosaurus “Mummy” Fossils Reveal Real Skin, Fleshy Crest, Hooves and Strange Spikes After 66 Million Years

Paleontologists have unveiled two extraordinary “mummy” specimens of the duck-billed dinosaur Edmontosaurus annectens, preserving the most complete external profile of any dinosaur ever reconstructed. These fossils, dating to approximately 66 million years ago, showcase authentic skin impressions, a prominent fleshy midline crest, a row of interlocking spikes along the tail, and the first known hooves in any dinosaur.

Discovered in Wyoming’s Lance Formation within a remarkable “mummy zone” of stacked river sands, the specimens include a late juvenile and an early adult. Published October 23, 2025, in Science by Paul C. Sereno and colleagues from the University of Chicago, the study details how a sub-millimeter clay film—formed through “clay templating” during early decay—captured every contour of the dinosaur’s body before soft tissues vanished. No original organic material survives; instead, the clay mask faithfully records pebble-like scales, wrinkled skin, and three-dimensional soft-tissue structures.

Most strikingly, a continuous fleshy crest runs from the neck over the trunk, transitioning at the hips into a single row of interdigitating spikes that extends to the tail tip. The hind feet reveal wedge-shaped hooves capping each toe—making Edmontosaurus the only dinosaur known to possess true hooves, likely aiding traction on floodplains. These features transform our image of hadrosaurs from plain duckbills into ornate, hoofed herbivores with dynamic midline ornamentation.

Housed at the University of Chicago and collaborating insтιтutions, the mummies offer an unprecedented window into Late Cretaceous life just before the asteroid impact. This discovery proves that even after 66 million years, exceptional preservation can still rewrite dinosaur appearance and ecology.