A groundbreaking discovery in Wyoming’s “mummy zone” has revolutionized our understanding of dinosaur appearance. Paleontologists from the University of Chicago have unveiled two remarkably preserved duck-billed dinosaur “mummies” that, through a process dubbed clay templating, showcase intricate details of scales, spikes, and even hooves, offering an unprecedented look at how these magnificent creatures truly appeared 66 million years ago.
For decades, our understanding of dinosaurs has been largely shaped by fossilized bones. While these skeletal remains provide incredible insights into size, structure, and locomotion, the intricate details of a dinosaur’s external appearance—its skin texture, crests, and unique features—have remained mostly a matter of educated guesswork. That era of speculation is now over, thanks to a remarkable discovery that is redefining paleontology. Experts from the University of Chicago have presented what they describe as the most complete “fleshed-out view” of a large dinosaur ever achieved, transforming our perception of the duck-billed dinosaur Edmontosaurus annectens.
The Breakthrough of Clay Templating
The secret to this unparalleled preservation lies in a unique process termed clay templating. While commonly referred to as “mummies,” these fossils are not akin to Egyptian mummies with preserved organic tissue. Instead, as explained by senior author Paul Sereno, professor of organismal biology and anatomy at UChicago, the preservation occurred through a “fluke event.” Approximately 66 million years ago, sun-dried dinosaur carcasses were suddenly buried in flash floods. A biofilm forming on the carcass surface then electrostatically attracted clay particles from the wet sediment, forming a wafer-thin mask—no more than 1/100th of an inch thick—that perfectly captured the dinosaur’s external features in three dimensions. Over longer timescales, the organic material decayed, and the skeleton below fossilized, leaving behind this incredibly detailed clay impression.
This intricate process required hours of careful work by the research team, led by fossil lab manager and co-author Tyler Keillor, to expose the paper-thin clay boundaries. Using an array of advanced imaging techniques, including hospital and micro-CT scans, thin sections, and X-ray spectroscopy, scientists were able to reconstruct the dinosaur’s true appearance in life. “This is a mask, a template, a clay layer so thin you could blow it away,” Sereno stated, emphasizing the delicate nature of this unique preservation method, as detailed in a paper published in the journal Science.
A Fleshed-Out Portrait: Crests, Spikes, and Scales
The paleontologists relocated historical sites in east-central Wyoming, where several famous dinosaur “mummies” were found in the early 20th century, mapping out a compact region now known as the “mummy zone.” Within this area, Sereno and his team excavated two new Edmontosaurus mummies—a late juvenile and an early adult—that offered large, continuous areas of preserved external skin surface. These two specimens beautifully complemented each other, allowing for the reconstruction of a complete, fleshy profile of Edmontosaurus annectens, a dinosaur that could grow to over 40 feet in length.
Key anatomical revelations include:
- A continuous midline feature that started as a fleshy crest along the neck and trunk.
- This crest transitioned into a single row of spikes running down the tail, with each spike precisely positioned over a single vertebra.
- The dinosaur’s skin was covered in surprisingly small, pebble-like scales, mostly 1-4 millimeters across, with larger polygonal scales on the lower body and tail.
- Wrinkles preserved over the rib cage suggest the skin was relatively thin.
The Shocking Discovery of Hooves
Perhaps the most astonishing detail revealed by these clay templates was the presence of hooves. The hind feet of the larger adult mummy showed that the tip of each of its three hind toes was encased in a wedge-shaped hoof with a flat bottom, much like those of a horse. This finding was cross-referenced with 3D images of the best-preserved duckbill footprints from the same geological period, confirming the hooved structure. Paul Sereno highlighted the significance of this discovery, stating, “There are so many amazing ‘firsts’ preserved in these duck-billed mummies—the earliest hooves documented in a land vertebrate, the first confirmed hooved reptile, and the first hooved four-legged animal with different forelimb and hindlimb posture.” This revelation overturns long-held assumptions about which animals developed hooves, demonstrating that mammals were not the first to evolve this trait.
Shaping the Future of Paleontological Research
Beyond the immediate anatomical breakthroughs, this research provides a comprehensive toolkit for future studies on dinosaur soft anatomy. This includes new preparation methods, a precise lexicon for describing soft structures and scales, an imaging workflow from fossil to flesh model, and a detailed “recipe” for understanding how dinosaur mummification via clay templating occurs. This new model for preservation opens doors for targeted searches for similarly preserved specimens in the same Wyoming strata and elsewhere, potentially leading to even more discoveries of dinosaur external features.
For the fan community and aspiring paleontologists, these findings are immensely exciting. Paul Sereno emphasized the importance of a collaborative approach, stating, “I believe it’s worth taking the time to assemble a dream team in order to generate science that can be appreciated by the general public.” The meticulous work by the UChicago Fossil Lab team, including digital artists who helped reconstruct the duckbill’s movement, brings these ancient creatures to life in a way never before possible. As more surprises are anticipated from the “mummy zone” and beyond, the full, fleshy profiles of dinosaurs are finally coming into view, thanks to these ancient clay masks.
For more detailed insights into this unique preservation and the findings, you can refer to the official University of Chicago Biological Sciences news release.
