In a groundbreaking study published in the prestigious journal Science, researchers from the University of Chicago have unveiled a novel process, termed "clay templating," that explains the remarkable preservation of soft tissues in dinosaur mummies. This discovery, centered on the duck-billed dinosaur Edmontosaurus annectens, offers an unparalleled glimpse into the appearance and anatomy of these ancient creatures as they existed approximately 66 million years ago. The meticulous research has allowed scientists to reconstruct the dinosaur’s physical characteristics with an astonishing level of detail, painting a vivid picture of a creature long speculated about but never before documented with such precision.
The process of "clay templating" describes how the delicate outer layers of the dinosaur’s body were preserved as an ultra-thin clay coating that settled over the skeleton after burial. This coating, less than one-hundredth of an inch thick, acted as a natural mold, capturing ephemeral features of skin, scales, and even hooves. Using a sophisticated array of advanced imaging techniques, the scientific team has successfully recreated a lifelike representation of the Edmontosaurus, revealing previously unknown anatomical traits.
Rediscovering Wyoming’s Dinosaur "Mummy Zone"
The key to this remarkable discovery lies in a specific geological area in east-central Wyoming, a region affectionately dubbed a "mummy zone" by paleontologists. Senior author Paul Sereno, PhD, a Professor of Organismal Biology and Anatomy at the University of Chicago, explained the significance of this location. "The badlands in Wyoming where the finds were made is a unique ‘mummy zone’ that has more surprises in store from fossils collected over years of visits by teams of university undergrads," he stated.
Sereno and his colleagues embarked on a dedicated effort to retrace the locations where significant dinosaur mummy finds were first reported in the early 20th century. Utilizing old field photographs and diligent detective work, they meticulously mapped a concentrated "mummy zone" within rock layers that represent ancient river sands. This focused approach led to the excavation of two new Edmontosaurus mummies, one representing a younger individual and the other a more mature specimen. Both of these fossils preserved extensive, continuous patches of the dinosaur’s external skin surface, providing the crucial data needed to construct a comprehensive profile of the animal.
It is important to distinguish these natural dinosaur mummies from the human-created mummies found in Egyptian tombs. As Sereno emphasizes, "none of the original organic material is still present." In both the newly described specimens and earlier examples identified as mummies, the preserved skin, spikes, and hooves are not actual tissue but rather an incredibly thin clay imprint. This delicate coating formed on the exterior of the carcass shortly after its burial. "This is a mask, a template, a clay layer so thin you could blow it away," Sereno remarked. "It was attracted to the outside of the carcass in a fluke event of preservation."
The Science Behind Clay Templating: A 3D Impression
The formation of these extraordinary fossils is attributed to a specific sequence of environmental events. The researchers propose that after death, the Edmontosaurus carcasses would have dried in the sun before being rapidly buried by sudden flash floods. During this process, a microbial film on the carcass’s outer surface played a crucial role. This film attracted clay particles from the surrounding wet sediment through electrostatic forces, effectively creating a wafer-thin clay template. This template faithfully captured the animal’s three-dimensional shape. Over vast geological timescales, the soft tissues would have decayed, leaving behind the fossilized clay impression and the skeleton.
To meticulously investigate this process, the research team employed a comprehensive suite of advanced imaging and analytical techniques. This included hospital-grade and micro-CT scans, thin section analysis, X-ray spectroscopy, and detailed clay mineral analyses, all correlated with a thorough study of the sedimentary rock layers where the fossils were discovered. Each line of evidence converged to support a specific scenario that resulted in this rare form of preservation.
Reconstructing the Duckbill: A Digital Renaissance
The delicate nature of the paper-thin clay layer presented significant challenges during the preparation phase. Fossil Lab manager Tyler Keillor, a co-author of the study, spearheaded hours of painstaking work to expose these critical surfaces without causing irreparable damage.
Following the careful preparation, another team, led by postdoctoral scholar Evan Saitta, utilized advanced 3D surface imaging and CT scans. They meticulously traced the preserved soft anatomy, examined the sediments both inside and outside the mummy, and critically, matched the dinosaur’s fossilized hooves to previously discovered fossilized footprints from the same geological period. This comparative analysis was vital in confirming the locomotion and posture of the Edmontosaurus.
The culmination of this detailed analysis involved digital artists working in close collaboration with the scientists. This interdisciplinary effort resulted in lifelike reconstructions that vividly illustrate how the Edmontosaurus would have appeared and moved as it traversed the muddy landscapes near the close of the dinosaur era. "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," Sereno commented, highlighting the broad appeal of their findings. "We’ve never been able to look at the appearance of a large prehistoric reptile like this – and just in time for Halloween."
Unveiling the Edmontosaurus: Crest, Spikes, Scales, and Thin Skin
Working with the two newly described mummies, the researchers were able to assemble a remarkably complete and fleshed-out outline of Edmontosaurus annectens. "The two specimens complemented each other beautifully," Sereno noted. "For the first time, we could see the whole profile rather than scattered patches."
One of the most significant revelations was the discovery of a continuous anatomical feature running along the center of the dinosaur’s back. This structure began as a fleshy crest over the neck and torso and transitioned into a single row of distinct spikes along the tail, with each spike precisely aligned above a vertebra and fitting snugly with its neighbors.
The study also provided unprecedented detail on the dinosaur’s scale patterns. The largest, polygonal scales were observed along the lower body and tail. The majority of the animal’s body, however, was covered in remarkably small, pebble-like scales, measuring only 1 to 4 millimeters across. This finding is particularly surprising given that Edmontosaurus could reach lengths exceeding 40 feet. Furthermore, fine wrinkles preserved over the ribcage suggest that the skin of this duck-billed dinosaur was relatively thin, a detail previously unconfirmed.
The Shocking Discovery: Hooves and Heel Pads on a "Hoofed" Dinosaur
Perhaps the most unexpected and groundbreaking discovery emerged from the hind feet of the larger mummy: this dinosaur possessed hooves. The tips of each of the three hind toes were encased in wedge-shaped hooves with flat undersides, strikingly similar in form to those of modern horses.
To gain a definitive understanding of these feet in life, the researchers integrated CT scans of the mummified feet with high-resolution 3D images of the most well-preserved duckbill footprint discovered from the same geological period. By meticulously aligning the skeletal structures and soft-tissue impressions, they generated a detailed reconstruction of the hind foot. A notable distinction from the forefoot, which only contacted the ground via its hooves, is that the hind feet also featured a fleshy heel pad located behind the hooves.
"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," Sereno stated, underscoring the profound implications of these findings. These discoveries challenge previous assumptions about dinosaur anatomy and evolution, particularly regarding the development of specialized foot structures.
A New Toolkit for Soft Tissue Paleontology
Beyond the exciting anatomical revelations, this research provides a robust and practical framework for future investigations into dinosaur soft tissue. The authors have outlined innovative preparation techniques, established a clear set of terminology for describing soft structures and scale types, and detailed a systematic imaging pathway from fossil specimen to lifelike reconstruction. Crucially, they have provided a scientifically grounded model for how dinosaur mummies can form under natural conditions.
Their work offers more than just a collection of isolated findings; it proposes a generalized model for dinosaur mummification based on the "clay templating" process. This model is now available for testing on other fossil specimens that may have formed under similar environmental circumstances, opening up new avenues of research across the paleontological community.
The research team has already identified several next steps for future investigations. These include focused searches for additional specimens exhibiting this exceptional preservation in the same Wyoming rock layers, as well as in other regions globally. Furthermore, they plan to conduct biomechanical studies that can now benefit from accurate external body outlines, and complementary analyses designed to elucidate the specific environmental conditions and locations where clay templating is most likely to occur.
Reflecting on the comprehensive nature of the study, Sereno concluded, "This may be the single best paper I’ve released. From field to lab to 3D reconstructions along with a suite of useful terms defined, it’s a tour de force, and it tells a coherent story about how these remarkable fossils come to be and what we can learn from them." This multidisciplinary approach, combining rigorous scientific analysis with artistic interpretation, has not only advanced our understanding of dinosaur biology but has also set a new standard for paleontological research. The implications of "clay templating" are far-reaching, promising to unlock further secrets about the ancient world and the creatures that inhabited it.
