Recent research conducted in the Lance Formation of eastern Wyoming has uncovered new insights into the preservation of dinosaurs, specifically large duck-billed species. This area, known for its rich fossil deposits, has yielded several remarkably well-preserved specimens, leading scientists to label it “the mummy zone.” The study, led by Dr. Paul Sereno, aims to clarify the unique preservation processes of these fossils and redefine the concept of a dinosaur “mummy.”
In the early 1900s, fossil hunter Charles Sternberg discovered two specimens of Edmontosaurus annectens in this formation. These skeletons exhibited such remarkable preservation that both Sternberg and H.F. Osborn, a paleontologist from the American Museum of Natural History, noted the existence of skin-like impressions and a fleshy crest along the dinosaur”s neck. Dr. Sereno described the initial find as potentially “the greatest dinosaur mummy,” a title he humorously suggested might be challenged by a juvenile specimen his team discovered in 2000.
Now, almost a century later, Sereno and his colleagues have analyzed two additional mummies from the same area, a juvenile and a young adult, using advanced techniques such as CT scanning and electron microscopy. Despite thorough examinations, the team found no remnants of soft tissue. Instead, they discovered a thin layer of clay, measuring less than one-hundredth of an inch thick, that had formed over the dinosaurs” skin. This clay layer created an astonishingly realistic impression of the underlying features.
Sereno proposes that the term “rendering” is more appropriate than “impression” to describe this preservation phenomenon. The research outlines the conditions that likely led to this unique preservation. During the Late Cretaceous Period, when Edmontosaurus inhabited what is now the American West, the climate alternated between drought and heavy monsoon rains. It is believed that drought was a factor in the deaths of the original specimens discovered by Sternberg, as well as other nearby fossils. Following their deaths, the carcasses would have dried under the sun, only to be buried quickly by a flash flood.
As the carcasses decomposed, they would have been enveloped in a bacterial film that attracted clay particles from the surrounding sediment. This thin layer of clay remained intact long after the organic materials had decayed, effectively creating a detailed clay mask that preserved the morphology of the dinosaurs” skin. According to Dr. Anthony Martin, a professor at Emory University, clay minerals have a remarkable ability to adhere to biological surfaces, allowing for an accurate representation of soft tissues, such as skin.
Dr. Stephanie Drumheller-Horton, a vertebrate paleontologist at the University of Tennessee, emphasized the importance of understanding fossilization processes. While dinosaur mummies have been studied for over a century, much of the focus has been on their physical characteristics rather than the mechanisms of their preservation. Gaining insight into how these fossils form can help researchers locate new specimens in the future.
The two newly analyzed mummies permitted Sereno and his team to reconstruct a more detailed image of what Edmontosaurus might have looked like. Their findings suggest that this dinosaur, which could reach lengths exceeding 12 meters, possessed a fleshy crest along its neck and back, accompanied by spikes along its tail. The clay mask also revealed that this dinosaur had hooves, marking it as the oldest land animal confirmed to possess this trait and the first known example of a hooved reptile. Sereno humorously remarked, “Sorry, mammals, you didn”t invent it,” indicating that while footprints suggested the presence of hooves, seeing the evidence was a confirmation.
This groundbreaking research has been published in the journal Science, contributing significantly to the field of paleontology and our understanding of dinosaur preservation.
