May 25 - September 8, 2013
The Tyrannosaurus rex has long commanded respect and sparked curiosity
in the mind of the public, and Sue is the most famous T. rex of all. At
42 feet (12.8 m) long and 12 feet (3.66 m) tall at the hips, her
skeleton inspires as much awe today as she did 67 million years ago.
by Chicago’s Field Museum, A T. rex Named Sue explores how this
remarkable creature interacted with its world and what we can learn from
studying its bones. Revel in the sheer size of a fully articulated,
life-sized skeleton cast, look a cast of Sue’s skull in the eye, and
experience Sue’s movement, vision, and sense of smell for yourself.
Touch casts of Sue’s bones and diagnose pathologies that left their mark
in Sue’s leg, jaw, and tail. Follow Sue’s sensational journey from the
Cretaceous to the rock of South Dakota to the U.S. courts, and
finally to the world. Learn about the technology used to prepare and
study this very special fossil.
Background History on Sue
was a Tyrannosaurus rex that roamed North America about 67 million years
ago. It was one of the last dinosaur species and one of the largest
flesh-eaters to have ever inhabited the Earth. The “Tyrant Lizard King,”
with its extraordinarily powerful jaws and massive serrated steak-knife
teeth, still dominates popular perceptions of the Age of Dinosaurs. The
T. rex is named for Sue Hendrickson, who discovered the dinosaur near
Faith, South Dakota, in the United States, during the summer of 1990 on a
commercial fossil hunting trip.
As the most complete T. rex
specimen ever discovered, Sue has tremendous value for scientists and
the general public. Previously, only a handful of partial T. rex
specimens had been found, none more than 60% complete. At 90% complete
and exquisitely preserved, Sue is the most celebrated member of its
species, permitting more detailed studies of the biology,growth, and
behavior of T. rex than had previously been possible.
Sue is the largest, most complete, best preserved Tyrannosaurus rex in the world. But exactly what does that mean?
Size: Sue's bones are bigger and more robust than any T. rex
specimen yet discovered. She sets the record for overall length (40.5
feet) and skeletal weight (3,922 pounds). Out of the more than 30 T. rex skeletons discovered so far, Sue's beefy bones beat them all.
Preservation: Virtually all parts of Sue's
skeleton are preserved in great detail—even the surface of her bones.
Scientists can actually see where muscles, tendons, and ligaments once
attached. And not only are most of the bones undistorted from
fossilization, but cross-sections of the bones show that even the
cellular structure inside remains intact.
Completion: Sue is more than 90% complete by bulk, meaning scientists have recovered more of each bone than for any other T. rex. Sue's bone count totals 224 of the 321 known bones, including many “firsts” found for T. rex, such as the furcula (wishbone), stapes (an ear bone), and almost all the gastralia (belly ribs).
Finding so many well-preserved bones for a single individual gives
scientists a rare chance to learn more about tyrannosaur anatomy and
Sue has helped us make important discoveries about T. rex:
Ear Bone. Sue is the first T. rex ever
found with a tiny ear bone called a stapes. The more than six-inch-long,
pencil-thin ear bone transmits sound vibrations from the eardrum to the
inner ear. This delicate ear bone is almost never preserved in dinosaur
fossils and promises to give scientists a better understanding of the
evolution of ear bones and hearing in dinosaurs and birds. The shape,
size and orientation of the external ear hole also may be a feature
unique to the tyrannosaurid family, including T. rex.
Wishbone. Sue’s skeleton includes the first furcula, or wishbone, ever found in a T. rex.
Present in bird skeletons, the wishbone provides evidence for
interpreting the relationship of advanced theropods (a group of
two-legged, meat-eating dinosaurs) to birds, the descendants of
dinosaurs. The furcula has also helped scientists investigate the
function of wishbones in dinosaurs.
Birdlike Leg Muscles. Soft tissues are almost never preserved in
dinosaurs, but Sue’s beautifully preserved bones reveal detailed
evidence of the attachments and orientations of the dinosaur’s limb
muscles. This has allowed scientists to reconstruct the most accurate
picture ever, from hip to foot, of the birdlike hind limb muscles in Tyrannosaurus.
Tail Muscles. A mass of gnarled, bony
overgrowths fusing two of Sue’s vertebrae together also preserves a
remarkable anatomical feature rarely seen in fossil dinosaurs: detailed,
natural mold impressions of tail muscles.
A Fast-Walking Dinosaur. Based on an analysis of Sue’s
well-preserved foot bones, Field Museum scientists have concluded that
Sue’s top speed was probably a fast walk of about 15 miles per hour,
about the maximum speed of an elephant. While this may seem slow for a T. rex, most of Sue’s dinosaur contemporaries would not have been nearly as swift.
The Neck Bone’s Connected to the Skull Bone.
Sue’s skeleton contains a pair of tiny bones that lie between the first
neck vertebra and the back of the skull. Called proatlas bones, these
are rarely seen in dinosaur fossils and are the first ever found in a T. rex.
Birds do not have proatlas bones. Their presence in both an advanced
theropod, such as T. rex, and in the ancient theropod Herrerasaurus may
help scientists tease apart anatomical transformations and evolutionary
relationships in the transition from advanced theropods to birds.
3-D Picture of the Skull. The
Field Museum’s research on Sue marked the first time that a
high-resolution, industrial x-ray scanner was used to create a detailed,
3-D image of the inside of a T. rex skull. (One famous early
study involved cutting a T. rex skull in half, altering the fossil
forever.) These CT images, interpreted by Field Museum paleontologists
and published in the Journal of Vertebrate
Paleontology, showed very large olfactory bulbs—indicating that Sue had a
keen sense of smell. Also discovered in the skull was a new air sinus
never seen before in a T. rex. Detailed analyses of the nerve passages in Sue’s braincase revealed new evidence from T. rex that birds are flying theropod (two-legged, meat-eating) dinosaurs.
A Sensitive Snout. An extensive series of holes in the upper jawbone of Sue’s skull appear to be aligned in a pattern. This observation, new to T. rex, suggests that the dinosaur’s snout was highly sensitive to touch.
New Clues to Evolutionary Relationships of Dinosaurs and Birds. Unusually well preserved fossils like Sue are invaluable for resolving debates about evolution. Field Museum researchers studying the 90-percent complete T. rex
skeleton and skull have discovered important new evidence supporting
the theory that birds are descended from theropod dinosaurs. Findings
include the wishbone, the birdlike limb muscles, birdlike air sacs
(pneumatization) throughout the skeleton and skull, and several features
in Sue’s braincase—revealed for the first time through high-resolution
x-ray (CT) images of the skull.
Living Fast. In a study featured on the cover of the journal Nature, scientists determined that T. rex
reached its massive adult size due to an extraordinary growth spurt
that stretched from about 14 to 18 years of age. Scientists studied the
bones of Sue and other T. rex specimens to find that, during the peak in its growth spurt, T. rex
gained 2.1 kilograms (4.6 pounds) per day, developing into a more than
5,000-kilogram (11,000-pound) giant, one of the largest terrestrial
carnivorous animals ever. T. rex grew faster but had a shorter lifespan than an African elephant, the only living land animal of a comparable size.
Dying Young. In the same study, scientists
discovered that Sue was 28 years old at the time of death. By counting
lines in tyrannosaurid bones that correspond to annual growth cycles,
researchers found that T. rex could live for about 30 years,
one-third of which would have been spent at adult size. Judging by
evidence of disease, arthritis, and broken bones, scientists believe
that Sue was a “train wreck” at death and probably died of natural
Tough Life of a Tyrannosaur. Sue’s bones
display several abnormalities, from a deformed right arm to jaws riddled
with holes. Initially, scientists assumed that these oddities were
battle wounds from clashes with other dinosaurs. Now scientists believe
most of Sue’s bone abnormalities are just
healed-over evidence of injuries, infections, and diseases—the normal
wear-and-tear of life in the Cretaceous.
Male or Female? Before Sue was found, body size and anatomical differences were used to speculate whether a T. rex was
male or female. One important clue was believed to be the location of a
v-shaped tail bone called a chevron. It had been suggested that Sue was
a female, based on the assumption that the first chevron was positioned
far from the pelvis in female crocodiles. But
after piecing together the skeleton, scientists discovered that Sue’s
first chevron was actually closer to the pelvis, more like that of males
in some living reptiles. After surveying living reptiles and other
theropod dinosaur specimens, Field Museum scientists concluded that the
position of the chevron varies too widely to make it a good indicator of
gender, even in modern reptiles. The bottom line is we may never know if Sue was male or female.
Was T. rex Warm-Blooded? More and more evidence
points to the fact that some dinosaurs were fast-moving, and perhaps
warm-blooded animals. Living warm-blooded birds and mammals (like
humans) have a series of bones in their nasal passages, called
turbinates, that help to warm and humidify air before it enters their
lungs. The x-ray scans of Sue’s skull allowed Field Museum scientists to
look for this warm-blooded feature for the first time in T. rex.
While thin bony structures were found in Sue’s nose, it was concluded
that they were not turbinates. This does not necessarily prove that T.
rex was not warm-blooded; it may mean that turbinates evolved later on
in the theropod-bird lineage, and that these dinosaurs had some other
mechanism for warming the air they breathed.
This exhibition was created by The Field Museum, Chicago, and made possible through the generosity of McDonald’s Corporation.
It is sponsored locally by First National Bank, the Douglas County
Commissioners, Valmont Industries, Inc., HDR, Inc., the Durham Society,
and the Peter Kiewit Foundation. Media support provided by WOWT.
Excavation Station sponsored by Thrasher Basement Systems, Inc.