In an extraordinary advancement in paleontology, researchers at the University of Chicago have unveiled a comprehensive reconstruction of the iconic duck-billed dinosaur Edmontosaurus annectens, offering an unprecedented glimpse into its soft tissue anatomy and external morphology through a novel preservation phenomenon termed “clay templating.” This innovative study, published in Science, sheds new light on the preservation processes that transformed carcasses into detailed dinosaur “mummies,” enabling visualization of scales, hooves, and distinctive crests with remarkable clarity.
The research centers on fossils unearthed from a concentrated “mummy zone” within the badlands of east-central Wyoming. This area has yielded multiple exquisitely preserved Edmontosaurus specimens over the past century, but only recently have advanced imaging technologies allowed scientists to decode the almost imperceptible sub-millimeter clay films that encapsulate these fossils’ surface details. Unlike traditional forms of fossilization that primarily conserve bone, the clay templating process created a delicate, exact mold of the dinosaur’s external flesh surface, capturing anatomical features otherwise lost to time.
Through meticulous fieldwork that included relocating historic excavation sites, the team recovered two new Edmontosaurus mummies—a late juvenile and an early adult—with large, contiguous regions of preserved skin. These specimens revealed that immediately after death, the carcasses underwent sun-drying before rapid burial by floodwaters, during which an electrostatically attracted clay film enveloped the exposed soft tissues. This clay mask, only a fraction of a millimeter thick, faithfully replicated the three-dimensional surface structure in extraordinary detail, effectively “mummifying” the dinosaurs without preserving organic tissue.
A suite of advanced analytical tools was employed to probe the fossils’ complex layering and chemical composition. High-resolution micro-CT scans unveiled the precise morphology of scales and skin textures, while X-ray spectroscopy and clay mineralogy analyses corroborated the presence of a thin, consistent clay layer that acted as a preservation template. These interdisciplinary methods collectively reconstructed the dinosaur’s soft anatomy with scientific assurance, transcending the fragmentary evidence traditionally available for such creatures.
One of the most striking revelations from these mummies is the presence of a continuous midline structure starting from a fleshy crest that extended along the neck and torso, morphing into a series of spikes running down the tail vertebrae. This anatomical feature had been hypothesized but never directly observed in such completeness, now providing invaluable insight into the integumentary adaptations of this species. Furthermore, the evidence suggests the skin was relatively thin and covered with a mix of large polygonal scales near the lower body and tail, while the rest of the body was adorned with tiny pebble-like scales mere millimeters in diameter.
Perhaps the most groundbreaking discovery pertains to the hind feet of Edmontosaurus. The research team found the toes sheathed in true hoof-like structures, similar in shape to horse hooves, a landmark identification constituting the earliest known instance of hooves in a terrestrial vertebrate. Combining CT scan data with footprints preserved in contemporaneous sediment, the team demonstrated that these hooves bore flat undersides and were complemented posteriorly by fleshy heel pads, indicating a distinctive locomotion style differing markedly from other dinosaurs and reptiles.
These exceptional findings redefine the morphological classification of Edmontosaurus, positioning it as the first confirmed hooved reptile with differentiated limb postures between fore and hind limbs. Such anatomical detail illuminates new ecological and behavioral considerations, painting a vivid portrait of a large herbivore navigating soft coastal mudflats during the final days of the dinosaur era. This knowledge enhances biomechanical modeling of dinosaur movement and footprint formation with precise, empirically based anatomical parameters.
Beyond providing an enhanced understanding of this species, the study lays a robust foundation for paleontological methods going forward. The research team articulates a detailed preparation protocol for revealing submillimeter clay masks, a refined lexicon for describing fossilized skin and soft tissue features, and an integrated imaging workflow that transitions seamlessly from fossil recovery to digital reconstruction. The clay templating model represents a paradigm shift in interpreting soft tissue fossilization, inviting targeted explorations for similar preservation in other strata globally.
The implications for paleobiology are profound, as the technique offers a powerful new lens through which to examine dinosaur skin, musculature, and integumentary structures that were previously known only from speculative assumptions or incomplete data. It opens avenues for multidisciplinary collaborations involving geochemistry, materials science, and digital animation to bring prehistoric life to vivid, scientific life. The detailed reconstructions not only further academic research but also enhance public engagement with dynamic visualizations of extinct creatures.
Senior author Professor Paul Sereno emphasized the rarity and importance of the discovery, describing it as the most complete fleshed-out view of a large dinosaur to date. The research’s timing, coinciding with Halloween, is serendipitous, allowing the public a thrilling and scientifically grounded experience of encountering a prehistoric giant as it would have appeared in its environment. The utilization of historical data, advanced imaging, and creative digital artistry embodies a truly holistic approach to paleontology.
The integration of fossil footprints alongside the mummified bodies provides a compelling narrative linking anatomical form to ecological function. This synergy underscores the value of preserving different fossil record elements from the same geological context to build a multi-faceted understanding. Postdoctoral researcher Evan Saitta’s contribution using 3D surface imaging was crucial in aligning skeletal structures with footprint evidence, solidifying interpretations of Edmontosaurus’ movement and gait mechanics.
As the team continues to investigate the Wyoming mummy zone and expand searches to equivalent deposits worldwide, the scientific community anticipates uncovering additional specimens displaying varying stages and modes of clay templating. Such future discoveries promise to refine evolutionary biology models and broaden knowledge of dinosaur diversity, physiology, and behaviors. The researchers envision these insights stimulating advancements in soft-tissue fossilization theories and paleontological digitization techniques.
Ultimately, this landmark study marks a transformative milestone in our quest to understand dinosaur biology through extraordinary preservation and interdisciplinary innovation. By unveiling the literal skin and hooves of Edmontosaurus annectens, it bridges millions of years to deliver a vivid glimpse of a dinosaur uniquely frozen in time—resurrected through the unprecedented clarity of its clay-cast exterior.
Subject of Research: Dinosaur fossil preservation and soft tissue reconstruction in Edmontosaurus annectens through clay templating
Article Title: [Not explicitly stated in the text]
News Publication Date: 23-Oct-2025
Web References: http://dx.doi.org/10.1126/science.adw3536
Image Credits: Artwork by Dani Navarro; storyboard by Jonathan Metzker; animation by Davide la Torre
Keywords: Dinosaur fossils, Paleontology
