She is 40.5 feet long and stands 13 feet tall when measured at her hip. And her fossil frame is almost complete.
Discovered and named after explorer and fossil collector by Sue Hendrickson in South Dakota in 1990, Sue is the largest, most extensive, and best preserved Tyrannosaurus rex specimens ever found. Before Sue’s discovery, palaeontologists had only ever discovered up to 60% complete fossils of T-rexes. The fact that 90% of Sue’s phenomenal fossil frame was found meant an incredible advancement in the understanding and study of this mighty species.
Sue is now a permanent feature at the Field Museum of Natural History in Chicago, Illinois, but it took a long way for her to end up there after her discovery.
In the summer of 1990, a team of paleontologist from the Black Hills Institute, located in Hill City, searched for fossils at the Cheyenne River Indian Reservation in western South Dakota. By the end of the summer, the group had discovered Edmontosaurus bones and was ready to leave.
When the group was about to depart, a flat tire was discovered on their truck so they decided to go to town the nearby town of Faith to have the truck repaired. One member, Sue Hendrickson, decided to stay though, with the aim 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. When she looked up to see where the bones had originated from, she saw larger bones protruding from the wall of the cliff. She returned to camp with two small pieces of bone and reported the discovery to Peter Larson, the president of the Black Hills Institute. By their distinctive contour and texture, Larson was able to establish that the bones were from a T. rex. Later, closer examination of the site showed many visible bones above the ground and some articulated vertebrae.
The scientists were also surprised by Sue’s large size and the excellent condition of her bones. The skull was 1,394 mm (54.9 in) long, and most of the teeth were still intact.
Although some of the crew had to depart, Hendrickson and a few other scientists began to uncover the bones. To the team’s great excitement, it turned out that much of the dinosaur had been preserved. Previously discovered T. rex skeletons were usually missing over half of their bones, but not this one.
It was later determined that Sue was a record 90 percent complete by bulk, and 73 percent complete if the elements are counted. Of the 360 known T. rex bones, around 250 have been recovered in the case speciment. The paleontologists believe that Sue was covered by water and mud soon after her death, preventing other animals from carrying away the bones. Additionally, the rushing water mixed the skeleton together, so most of the bones remained in one place. When the fossil was found, the hip bones were above the skull and the leg bones were intertwined with the ribs.
Soon after the fossils were found, a dispute arose over their legal ownership, and in 1992 the FBI and the South Dakota National Guard eventually raided the site where the scientists from Black Hills Institute had been cleaning the bones and seized the fossil.
After a lengthy civil case, the court decreed that Maurice Williams, the owner of the land who orginally sold the fossil to the director of the instutute, retained ownership. Williams then decided to auction the property, which made many people worried that the fossil would end up in a private collection where the public would not be able to observe it. Also concerned about this possibility, the Field Museum in Chicago and decided to attempt to purchase Sue. However, the organization realized that they might have had difficulty securing funding and requested that companies and private citizens provide financial support. With their financial support, the Field Museum finally managed to purchase the remains with the highest bid of US$7.6 million. The final cost was US$8,362,500, which was then the highest amount ever paid for a dinosaur fossil.
Close examination of the bones revealed that Sue was 28 years old at the time of death – the oldest T. rex known until Trix was found in 2013. During its long life, this carnivore received several injuries and suffered from numerous pathologies. She has a damaged shoulder blade, a torn tendon in the right arm due most likely from a struggle with prey, and three broken ribs. The left fibula is twice the diameter of the right one, likely the result of infection. Multiple holes in the front of the skull have been found to be areas of parasitic infection, possibly from an infestation of an ancestral form of Trichomonas gallinae, a protozoan parasite that infests birds and ultimately leads to death by starvation due to internal swelling of the neck. Some of the tail vertebrae are fused in a pattern typical of arthritis due to injury. The animal is also believed to have suffered from gout.
So we definitely know that the animal had a tough life. But we don’t know how it died. Scholars debate exactly how thgat happen, but the cause of death is ultimately unknown.
Sue has a length of 12.3–12.8 meters (40–42 ft), stands 4 meters (13 ft) tall at the hips, and has been estimated to weigh between 8.4–14 metric tons. Displayed separately from the whole body, the skull weighs 272 kg (600 lb).
In addition, the longest known gastralium (belly rib) among theropods, measuring about 90 centimeters (3.0 ft), is known from this specimen. Sue also has the longest known pubis currently measured among the Cretaceous theropods, measuring roughly 136 centimeters (4.46 ft).
Given that T-rexes lived about 68 to 66 million years ago, their bones are hardly ever found in such a good condition. Sue is a unique exception, but then, who knows what’s still there, under the ground?