In bone blasted from Montana sandstone, fossil hunters for the first time have discovered the microscopic soft tissue of a Tyrannosaurus rex, preserved almost unaltered inside a bone since the dinosaur died 70 million years ago, scientists announced Thursday.
Scientists at North Carolina State University and at Montana State University's Museum of the Rockies in Bozeman found brownish oblong cells, elastic threads of veins and pliable dabs of red bone marrow in the core of a stout hind leg, the researchers reported in the journal Science.
The translucent vessels were so elastic that when one was stretched out and then released, it snapped back like a rubber band.
"To my knowledge, preservation to this extent has not been noted in dinosaurs before," said Mary H. Schweitzer, a paleontologist at North Carolina State University in Raleigh.
"The tissues are still soft," said Schweitzer, who led the research team. "The microstructures that look like cells are preserved in every way."
Under a scanning electron microscope, these dinosaur tissues -- minute remains of the mightiest of Earth's ancient carnivores -- were "virtually identical" to those of a modern ostrich.
The scientists have not completed their laboratory tests, so they would not say whether they had found any intact genetic material or had isolated individual proteins.
In the unlikely event that researchers could identify the actual genes of a Tyrannosaurus rex, it might help settle debates about the kinship of dinosaurs and birds, or even prompt efforts to clone Tyrannosaurus rex.
Far from a freakish accident of preservation, fragile fresh tissue inside dinosaur bones may turn out to be common, the researchers said. Indeed, a quick examination of three other dinosaur specimens revealed similar microscopic tissues inside the bones, they said.
The scientists' discovery began with happenstance: Fieldworkers had to break the massive thighbone to load it onto a helicopter. Normally, "people tend not to want their dinosaurs broken, or to have holes cut into the bone, or to cut them in half," said John R. Horner, a Montana State paleontologist and a co-author of the study.
"It may be that this isn't a unique specimen," said Horner, who has pioneered the use of molecular and cellular techniques to study the growth and behavior of dinosaurs.
If confirmed by other researchers, the find could force scientists to reconsider how all fossils are formed.
Until now, scientists have believed that bones fossilized when minerals gradually replaced organic material. Under current theories, organic molecules should not last more than 100,000 years.
"Our theories don't allow for this," Schweitzer said.
Other researchers were fascinated, but cautious about the announcement.
The field of dinosaur studies is an academic netherworld where paleontologists must compete for specimens with rockhounds and private collectors. It is no stranger to outlandish technical claims, black- market hyperbole and fraud.
Time and again, however, the truth of the vanished reptilian denizens as revealed by reliable fossils -- creatures that flew on four wings, snake-necked vegetarians larger than locomotives, and giant fanged predators cloaked in feathers -- has proved far stranger than fiction.
Philip Currie, curator of dinosaurs at the Royal Tyrrell Museum in British Columbia, considered the latest discovery plausible and called it "great news."
"Under the right circumstances, incredible things can be preserved in these fossils," Currie said.
But he added: "It is out on the fringes and consequently you have to be doubly careful."
In the curio cabinet of time, researchers have discovered a surprising array of primeval remains preserved mostly as life left them, including a 40-million-year-old bumblebee captured in amber, a 40,000-year-old woolly mammoth calf preserved in permafrost and an 8,000-year-old human brain buried in a bog.
In recent years, dinosaur diggers also have uncovered detailed impressions in layered sediments of feathers, embryos, skin and internal organs from the era of dinosaurs 65 million to 250 million years ago. In those fossils, the delicate pliable tissues survive only as a memory in stone.
Microscopic traces of soft tissues may have eluded detection until now, the scientists said, because paleontologists were too squeamish to break open their irreplaceable dinosaur specimens to dissolve the mineral matrix inside the bones.
Horner called the discovery a combination of adept laboratory analysis and an accident of fieldwork.
The tissue specimen was extracted from a fossil femur chiseled from 1,000 cubic yards of rock in the Hell Creek Formation at the Charles M. Russell National Wildlife Refuge in Montana. The bones belonged to a fairly complete skeleton of a 40-foot-tall Tyrannosaurus rex that died when it was about 18 years old.
It took field researchers three years to dig out all the bones. So remote was the site that the fossils could only be removed by helicopter.
The remains of the dinosaur were encased in thick jackets of plaster and were so heavy that fieldworkers had to break the thighbone in two places to load it aboard the aircraft. They also did not treat it with the customary chemical preservatives.
"On that particular specimen, it was serendipitous because we did have to break it to get it out by helicopter," Horner said.
The broken thighbone was delivered to the Raleigh lab of Schweitzer, who noticed what appeared to be unusual tissue fragments lining the narrow cavity at the core of the bone.
It took seven days to dissolve the surrounding minerals without contaminating the specimen. For weeks more, the samples were washed in chemical baths, incubated and purified.
In the process, Schweitzer essentially distilled the remains of a 5-ton predator whose step once made the earth tremble to a few milliliters of cloudy solution under a Zeiss dissecting microscope.
Magnifying the purified remains by 63 times, Schweitzer could see branching red and brown structures that looked very much like vessels in bones from the largest of modern flightless birds. She also identified what seemed to be three different sorts of cell.
"Ostriches that died six months ago are producing structures that are similar to dinosaurs that died 70 million years ago," she said.