Dinosaur "Mummies" Reveal Hooves and Crests, Redefining Edmontosaurus Appearance

Paleontologists from the University of Chicago have unveiled groundbreaking insights into the duck-billed dinosaur Edmontosaurus annectens, thanks to exceptionally preserved "mummies" discovered in Wyoming. This research, published recently in the journal Science, provides an unprecedentedly clear picture of the dinosaur's external appearance and locomotion, challenging long-held assumptions about its features.

The remarkable fossils, unearthed in a region dubbed the "mummy zone" in east-central Wyoming, reveal intricate details including scales, hooves, and a fleshy crest. According to CBS News on October 27, 2025, these specimens were preserved through a unique process called "clay templating," where a thin clay mask molded the dinosaur's external fleshy surface.

This innovative research, led by renowned University of Chicago paleontologist Professor Paul Sereno, has fundamentally reshaped our understanding of hadrosaurs. Sereno emphasized in a UChicago news release that the "mummies" are not preserved organic tissue but rather delicate clay molds, offering a three-dimensional template of the dinosaur's form.

Among the most surprising revelations, as reported by iflscience on October 24, 2025, is the discovery of hooves on the dinosaur's feet, making Edmontosaurus the first confirmed hooved reptile. This finding, along with evidence of a continuous midline feature including a fleshy crest and spikes, provides a complete, fleshed-out view of the large dinosaur.

The team utilized advanced imaging techniques, including hospital and micro-CT scans, to reconstruct the dinosaur's anatomy with extraordinary precision. sci.news reported on October 23, 2025, that these methods allowed scientists to visualize features that were previously only speculated, offering a robust foundation for future paleontological studies.

This discovery not only illuminates the physical characteristics of Edmontosaurus annectens but also sheds light on the rare taphonomic conditions required for such preservation. The University of Chicago stated that the process involved a rapid burial by flash floods, followed by a biofilm attracting clay minerals to form the protective mask.

• Unusual Preservation Mechanism: "Clay Templating" The exceptional preservation of these Edmontosaurus annectens specimens is attributed to a rare process termed "clay templating." Unlike typical fossilization that occurs in oxygen-poor environments, these dinosaur mummies were found in coarse, oxygenated river deposits in Wyoming, as noted by Mirage News on October 23, 2025. After the dinosaur's death, its carcass likely desiccated in the sun before being rapidly buried by a flash flood. A thin biofilm then formed on the decaying surface, electrostatically attracting clay minerals from the wet sediment to create a wafer-thin, sub-millimeter clay mask that captured the external features before the organic material decayed.

• First Confirmed Hooved Reptile and Earliest Land Vertebrate Hooves One of the most astonishing findings from this research is the presence of hooves on Edmontosaurus annectens. According to cbc on October 27, 2025, CT scans revealed wedge-shaped hooves with flat bottoms encasing the dinosaur's toes. This discovery marks the first time hooves have been found on a dinosaur and, indeed, on any reptile, making Edmontosaurus the earliest known hooved reptile and the bearer of the earliest hooves documented in a land vertebrate. Professor Paul Sereno highlighted the significance of this, stating it was a major surprise.

• Detailed External Anatomy: Crests, Spikes, and Scales The "mummies" provided an unprecedented level of detail regarding the dinosaur's external anatomy. Researchers reconstructed a continuous midline feature, beginning as a fleshy crest along the neck and trunk, transitioning into a row of spikes over the hips and tail, with each spike positioned precisely over a vertebra, CBS News reported on October 27, 2025. The skin was covered in intricate polygonal scales, surprisingly small (1-4 millimeters) for a dinosaur that could grow up to 40 feet. These features offer a comprehensive and confident reconstruction of the dinosaur's appearance.

• The "Mummy Zone" and New Discoveries The research team, led by Professor Paul Sereno, revisited the historical sites in east-central Wyoming where similar dinosaur mummies were found in the early 20th century, mapping out a specific "mummy zone." In this zone, they excavated two new Edmontosaurus mummies: a late juvenile and an early adult. The juvenile specimen is particularly significant as the first subadult dinosaur mummy and the first large-bodied dinosaur with a fully preserved fleshy outline, including a neck and trunk crest, as reported by Mirage News on October 23, 2025.

• Implications for Dinosaur Biology and Paleontology These findings have profound implications for our understanding of dinosaur biology and the field of paleontology. The detailed external features, particularly the hooves, suggest new insights into the locomotion and adaptations of hadrosaurs, which were common plant-eating dinosaurs during the Late Cretaceous period. The study also provides a new model for dinosaur mummification, offering a toolkit for future research on dinosaur soft anatomy and challenging previous assumptions about how such fossils were formed and preserved, according to geneonline News on October 27, 2025.

• Advanced Imaging and Collaborative Research The University of Chicago team employed a suite of advanced imaging tools, including hospital and micro-CT scans, thin sections, and X-ray spectroscopy, to analyze the delicate clay templates. This multidisciplinary approach allowed them to reconstruct the dinosaur's fleshy appearance and movement. Professor Sereno emphasized the importance of assembling a "dream team," including digital artists like Tyler Keillor, to generate science that is both accurate and accessible to the general public, as stated by CBS News on October 27, 2025.