UChicago paleontologists unveil duck-billed dinosaur ‘mummies’.

Paleontologists at the University of Chicago have revealed remarkably preserved fossils of the duck-billed dinosaur Edmontosaurus annectens, nicknamed “mummies,” from Wyoming’s badlands. These 66-million-year-old fossils aren’t organic mummies like humans, but were preserved via a paper-thin clay layer that captured the dinosaur’s external skin, scales, spikes, and surprisingly, hoofed toes—the earliest hooves ever documented in a land vertebrate.

Using CT scans, micro-imaging, and 3D reconstruction, researchers created a detailed life-like profile of the dinosaur: a tall crest along the neck and trunk, a row of spikes along the tail, and hind feet with hooves fitted to fossilized footprints. The discovery not only illuminates the appearance and movement of Edmontosaurus, but also establishes a new model of dinosaur “mummification” via clay templating.

This breakthrough opens doors for future studies of dinosaur soft anatomy, biomechanical models, and targeted searches for similarly preserved specimens.

A Dinosaur Frozen in Time

Paleontologists at the University of Chicago have revealed extraordinary fossils of Edmontosaurus annectens, a duck-billed dinosaur from Wyoming’s badlands, preserved in stunning detail. Unlike human mummies, these 66-million-year-old specimens were preserved through a phenomenon called clay templating, where a wafer-thin layer of clay—less than 1/100th of an inch thick—formed over the carcass, capturing skin, scales, and even soft tissue shapes. This preservation provides an unprecedented view of the dinosaur’s external anatomy, offering insights into how these creatures really looked and moved.

From Field to Lab: Reconstructing Life

The team excavated two mummies—a juvenile and an adult—mapping a “mummy zone” where historical specimens had been found. Using CT scans, micro-imaging, and sediment analysis, they reconstructed the dinosaurs’ fleshed-out appearance. A tall crest ran along the neck and trunk, a row of spikes ran down the tail, and the skin displayed tiny pebble-like scales and larger polygonal scales on the lower body. This detailed reconstruction marks the first time scientists can visualize a complete profile rather than scattered patches of skin.

A Surprising Discovery: Hooves

The most astonishing find was the hind feet. Each of the three toes was encased in a wedge-shaped hoof, making Edmontosaurus the earliest known hooved land vertebrate. By comparing CT scans of the mummies’ feet with fossilized footprints, researchers accurately reconstructed the posture and movement of the dinosaur, revealing a fleshy heel pad behind the hooves and highlighting differences between forelimb and hindlimb structure. This discovery redefines our understanding of dinosaur anatomy and locomotion.

A New Model for Dinosaur Soft-Tissue Research

Beyond anatomical insights, the study provides a blueprint for future research. The team developed preparation methods, a lexicon for describing soft structures and scales, and a 3D imaging workflow from fossil to fleshed-out model. Clay templating emerges as a valuable method for preserving and analyzing soft tissue in other fossils. Researchers plan to apply these techniques to locate more mummies in Wyoming and beyond, and to refine biomechanical models based on reliable external anatomy.

A Tour de Force in Paleontology

Senior author Paul Sereno describes the study as a landmark achievement. From fieldwork to lab analysis to digital reconstruction, the research provides a coherent story of how these fossils formed and what they reveal about dinosaur biology. It combines careful scientific rigor with visually compelling reconstructions, offering the public a rare glimpse of a fully realized prehistoric reptile.