During the summer of 1990, a group of workers from the Black Hills Institute, located in Hill City, searched for fossils at the Cheyenne River Indian Reservation in Western South Dakota near the city of Faith. By the end of the summer, the group had discovered Edmontosaurus bones and was ready to leave. However, a flat tire was discovered on their truck before the group could depart on August 12. While the rest of the group went into town to repair the truck, Sue Hendrickson decided to explore the nearby cliffs that the group had not checked. As she was walking along the base of a cliff, she discovered some small pieces of bone. She looked above her to see where the bones had originated, and observed larger bones protruding from the wall of the cliff. She returned to camp with two small pieces of the bones and reported the discovery to the president of the Black Hills Institute, Peter Larson. He determined that the bones were from a T-Rex by their distinctive contour and texture. Later, closer examination of the site showed many visible bones above the ground and some articulated vertebrae. The crew ordered extra plaster and, although some of the crew had to depart, Hendrickson and a few other workers began to uncover the bones. The group was excited, as it was evident that much of the dinosaur had been preserved. Previously discovered-Rex skeletons were usually missing over half of their bones. It was later ascertained that Sue was a record 80 percent complete. Scientists believe that this specimen was covered by water and mud soon after its death which prevented other animals from carrying away the bones. Additionally, the rushing water mixed the skeleton together. When the fossil was found the hip bones were above the skull and the leg bones were intertwined with the ribs. The large size and the excellent condition of the bones were also surprising. The skull was nearly five feet long and most of the teeth were still intact. After the group completed excavating the bones, each vertebra was covered in burlap and coated in plaster, followed by a transfer to the offices of The Black Hills Institute where preparations began to clean the bones.
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