Badlands Mummification
Horseshoe Canyon cuts through layers of rock from the Late Cretaceous period, exposing the 74 to 67-million-year-old Horseshoe Canyon Formation. This geological unit contains many dinosaur fossils, including those of the large, plant-eating hadrosaur, Edmontosaurus regalis. In rare cases, the conditions here led to the formation of "dinosaur mummies." These are not mummies in the Egyptian sense, with preserved organic material. Instead, they are exceptionally detailed fossils where impressions of skin and other soft tissues are preserved in the surrounding rock.
This remarkable preservation happens when a dinosaur's body is buried rapidly in fine-grained sediment, like silt or mud from an overflowing river. The rapid burial protects the carcass from scavengers and the elements. Before the skin and other tissues could completely decompose, minerals in the sediment created a natural cast, preserving the texture and shape of the animal's exterior. Sometimes, a thin film of clay, attracted to the decaying body by microbial action, would form a precise template of the skin's surface.
Reading the Skin
Finds in and around Horseshoe Canyon have given paleontologists a clear picture of hadrosaur skin. Unlike modern lizards, the skin of Edmontosaurus was not covered in large, overlapping scales. Instead, it was a mosaic of non-overlapping bumps called tubercles or scales, which varied in size from 1 to 5 millimeters in diameter. These pebbly skin textures show that hadrosaurs were complex in their appearance compared to the smooth-skinned animals of early reconstructions.
While the most famous dinosaur mummies with stomach contents, like the nodosaur Borealopelta and the hadrosaur "Dakota," were found in other parts of Alberta and North America, they show the scientific importance of such preservation. These specimens show details about dinosaur diets. For example, the stomach contents of Borealopelta showed it was a selective feeder, primarily eating specific types of ferns. In a juvenile Gorgosaurus (a tyrannosaur) found in nearby Dinosaur Provincial Park, the remains of two small, bird-like dinosaurs were found in its stomach cavity, revealing the diet of young predators. Discoveries of hadrosaur remains are common in Horseshoe Canyon, with ongoing excavations regularly uncovering new skeletons. Each find may reveal more details about the lives of these Cretaceous animals.