For Immediate Release November 8, 1999 Contact: Pat Kremer (312) 665-7100 Science Backgrounder SUE: MORE THAN JUST A PRETTY FACE At The Field Museum, Scientists Study Sue Inside and Out Since 1900, when the first Tyrannosaurus rex fossil was unearthed, the menacing dinosaur with the powerful jaws has become one of the best known pop culture icons in history. From silent films to "Jurassic Park," in comic books and novels, at toy stores and theme parks, T. rex is king to dinosaur enthusiasts of all ages. So popular is the dinosaur that it’s easy to forget that T. rex is every bit as important to research scientists as it is to 7-year-olds. The acquisition of Sue, the world’s largest and most complete T. rex specimen, by Chicago’s Field Museum (with assistance from McDonald’s® Corporation and Walt Disney World Resort®) is exciting news to scientists. Here the fragile bones have been painstakingly cleaned and repaired in the McDonald’s Fossil Preparation Lab. And here she will be cared for by experts and studied by scientists from The Field Museum and institutions around the world. Already the Museum’s paleontologists are examining the skeleton with both traditional methods and cutting-edge technologies, extending the limits of what is known—and what can be discovered—about this incredible species. Adding pieces to the evolutionary puzzle Was T. rex a predator, a scavenger, or both? Was it warm-blooded like birds or cold-blooded like crocodiles? How did it grow? How did it stand, move, eat, live? What use were its relatively puny arms? How much did it rely on its eyesight, hearing, and sense of smell? What sorts of illnesses and injuries plagued it, and how did it recover? And most important of all, how is T. rex related to other dinosaurs of its time, and to species that lived before and after it? T. rex may be familiar to virtually everyone, but what we don’t know about the creature would fill volumes, according to paleontologist Chris Brochu, a research associate at The Field Museum and the lead researcher on Sue. "Look at the literature on ancient crocodiles," Brochu says. "It’s huge—it fills shelf after shelf after shelf. By comparison, the literature on tyrannosaurids—the dinosaur family Sue belongs to—makes a very small stack, maybe a couple of feet high." Brochu will add a major volume to that stack when he completes the monograph on Sue. The monograph is a full scientific description of this specimen, complete with detailed measurements and images of all her bones and anatomical structures. It will serve as a reference for all future work on T. rex. "You can’t do anything with a fossil till you know what’s there," Brochu explains. "Sue’s completeness will let us do that to a far greater extent—and with far greater confidence—than it’s ever been done." Only four other T. rex specimens are even as much as 60% complete; Sue, in contrast, is 90% complete and possesses one of only two existing T. rex forelimbs. Her completeness, combined with the exquisite preservation of the bones, makes Sue an invaluable resource for those studying this species. "Because we have all the important pieces from a single animal," says Brochu, "we’ll be able to start drawing conclusions about its motion, its growth, and the relationship of T. rex to other dinosaur species." Those relationships are especially important to Brochu. He calls himself a "tree hugger"—his special interest is phylogeny, the study of evolutionary family trees. By looking at key features an animal shares with other species—such as the shape of its foot bones or the holes in its skull—scientists like Brochu determine a creature’s place in the evolutionary tree. This, in turn, allows them to study and test theories about evolutionary processes, ancient ecosystems, even plate tectonics, the breakup and movement of continental plates. "This skeleton is just filled with information," adds Barbara Ceiga, senior exhibit developer. "With the right people looking at it in the right ways, the stories will come tumbling out." Sue, Her Life and Times Among the stories hidden in Sue’s massive bones are clues to what life is life at the extreme. At close to 45 feet long, Sue is one of the largest creatures ever to walk on two legs. Even as dinosaurs go, she is huge; scientists estimate that in life she weighed seven tons—14,000 pounds. How did she get that big? By surviving. Unlike mammals—but like most other reptiles—dinosaurs continued to grow even after reaching adulthood. The longer they lived, the bigger they grew. What happens to bones and muscles when something gets as big as Sue? How do the various systems function? Sue will add significantly to our understanding of the biomechanics of T. rex, as scientists study how her huge head, her massive legs and tiny forelimbs, and her long tail and powerful jaws all worked together, allowing her to stand and move, to catch prey and eat enough to support her tremendous bulk. Of major importance in such studies are the astonishing quality of preservation and the expert preparation of Sue’s bones. Sixty-seven million years after her death, it’s still possible to see fine surface details showing where muscles, tendons, and other soft tissues attached to the bone. These details allow scientists like Field Museum Research Associate Matt Carrano to reconstruct what Sue might have looked like in life, her range of motion, and how she moved or rested. The conclusions Carrano has drawn form the scientific basis for the pose of Sue’s skeleton in the exhibition. Some details of Sue’s skeleton may reveal more extraordinary events in her life. A number of her bones show pathologies; there are holes, scars, masses, and even two misshapen teeth. A number of the wounds were at first thought to be bite marks and battle scars. But Chris Brochu, consulting with a paleopathologist (a scientist who studies disease and injury in fossils and other remains), now thinks most of the lesions were probably caused by infections. "What’s interesting," Brochu points out, "is that Sue didn’t die from any of these wounds. They all show extensive healing, a sign of good health. At this point it looks like Sue lived a good, long life—and then she just died." Brochu is also interested in other ways in which Sue interacted with the world—especially through her senses. Because soft tissues don’t fossilize, it’s difficult to say just how a prehistoric animal saw or heard, smelled or tasted. "We do know that Sue could see and hear, because we can tell from the bone structure and the nerve openings that these systems are well built," Brochu says. But even more impressive are her enormous olfactory bulbs, twin structures located at the front end of the brain, devoted to detecting smells. They’re nearly as large as the brain itself—an indication that the sense of smell played a very significant role in the life of T. rex. "When Sue explored the world," says Brochu, "it was nose-first." The Age of Dinosaurs Meets the Age of Computers The spaces that held Sue’s olfactory bulbs—as well as openings for nerves and blood vessels, bony structures surrounding the delicate semicircular canals of her inner ear, and other hidden features of her skull—were revealed by CT scanning technology. That extraordinary procedure was a breakthrough in its own right. In August, 1998, Sue’s 5-foot-long skull was carefully wrapped and crated, flown to the Boeing Company’s Rocketdyne lab in Ventura County, California, hoisted up by crane and bolted to an industrial-strength computerized tomographic scanner normally used for examining jet engines. There it underwent more than 500 hours of x-ray scanning, subjecting it, according to the tongue-in-cheek calculation of one Boeing technician, to "more radiation than Godzilla received when the French A-bomb was detonated in Polynesia." "This was the first time industrial, rather than medical, CT technology has been used to examine a T. rex," says Chris Brochu. "It’s allowed us to go where no paleontologist has gone before—inside Sue’s head. It’s the first time anyone has been able to look inside a T. rex skull without breaking or destroying any part of it." The 748 CT images—each an x-ray "slice" of the skull—fill eight CDs. They can be viewed individually or stacked to create a 3-dimensional image of Sue’s skull and snout. With the help of a computer program, it’s now possible to take a virtual journey through a real T. rex head—travel through narrow passages, look behind bony walls, pan around in every direction, even slip inside the bone itself. Much of this is uncharted territory, and it’s opening up entire new areas of study for scientists, as well as new possibilities for examining other fossils. The CT pictures also helped enormously in the work of preparing and preserving Sue. "Fossil preparation is expert work," explains Barbara Ceiga. "Preparators use tiny dental tools, miniature ‘sand blasters’ (they actually use baking soda), and meticulous techniques to clear away the matrix [the rock in which the fossil is embedded] and reveal the tiniest surface details. They make delicate, invisible repairs and fit together broken fragments with special glues. "It’s slow, painstaking work—and it’s extremely important. Because our job is not just to prepare Sue for research. It’s to keep her safe forever."