Paleontologists have recovered what appear to be soft tissues from the thighbone of a 70 million-year-old Tyrannosaurus rex, potentially enabling dinosaur research to make a leap into studying the animals' physiology and perhaps even their cell biology, the research team said yesterday.
Working with the remains of a T. rex unearthed in northeastern Montana's celebrated Hell Creek formation, the paleontologists spied the soft tissue when they were forced to break the thighbone into pieces to fit it aboard a helicopter.
The 67 million-year-old skeleton known as Sue, which was discovered in 1990 near Faith, S.D., is the largest, most complete and best-preserved Tyrannosaurus rex.
(Mark Wilson -- Getty Images)
Once in the lab, the team systematically removed mineralized deposits from the bone, exposing blood vessels, bone cells and possibly intact blood cells with their nuclei. "The tissues are still soft, transparent and flexible, and we can manipulate the vessels with our probe," said team leader Mary H. Schweitzer of North Carolina State University.
News of the discovery, reported in this week's edition of the journal Science, amazed many scientists. "It's a tremendous thing," Ohio University paleontologist Lawrence M. Witmer said. "It's the first time for anything this old, and if we can start getting the biomolecules of these animals, that will take us to a place we have never been."
Schweitzer said the team is conducting further chemical analysis to determine whether individual proteins could be isolated from the specimen. She said she did not know whether it would be possible to recover DNA from the thighbone.
But "there's no 'Jurassic Park' scenario," said paleontologist Hans-Dieter Sues, associate director of research and collections at the National Museum of Natural History, adding that the bone is so old that DNA fragments are probably the best that could be hoped for.
Still, he added, the ability to isolate soft tissues, by itself, opened up research horizons never before imagined. "We would have insights into all kinds of things -- diet, sexual maturity, whether the specimen is the male or female," Sues said. "There's a lot of biological information locked up in this material."
Scientists have frequently found indirect evidence of soft tissues in fossils, with the outlines of bird and, increasingly, dinosaur feathers, fish fins or leaf outlines appearing in ancient sedimentary beds.
Fossilized trees also appear as mineralized "petrified wood," and insects and lizards have been found in amber -- fossilized tree sap. Also, large, partly fossilized mammoths and other animals, and even ancient humans, have been found virtually intact in bogs or frozen in ice, but those beasts and humans lived long after the dinosaurs disappeared.
Research team member John R. Horner of Montana State University's Museum of the Rockies said the skeleton of a smallish but mature T. rex, about 18 years old, was found beneath 1,000 cubic yards of sandstone at the base of the Hell Creek formation along the Missouri River in northeastern Montana.
Hell Creek has produced fossils of hundreds of animal species that lived between 70 million and 65 million years ago, including ancient clams, sharks, sturgeon, turtles, lizards, crocodiles, small mammals and about two dozen species of dinosaurs.
Horner, speaking with Schweitzer during a telephone news conference, described the T. rex discovery as "a fantastic specimen" that took three years to excavate. The site is so remote that pieces of the skeleton had to be transported by helicopter to the Museum of the Rockies.
"We have a laboratory where we do cellular and molecular paleontology, so we do cut into bones," Horner acknowledged. Still, he added, the discovery of what appeared to be soft tissues in the matrix of the fossilized femur was "serendipitous" because the team broke the femur simply because it would not otherwise fit in the helicopter.
The lab work was supervised by Schweitzer, a paleontologist with experience in forensic analysis of modern biological samples, an advantage in a profession in which backgrounds in geology or other earth sciences are more common.
Schweitzer explained that bone requires a good blood supply and is "infiltrated" with many blood vessels, which bring in "bone-specific" cells known as osteocytes and follow with the calcium that makes the hard tissue.
"What we did was try to work backwards," Schweitzer said, using modern methods to remove the mineralized calcium until they exposed the blood vessels and osteocytes, along with a fibrous matrix, probably composed mostly of collagen, a common protein in animals.
The team also found small reddish-brown "dots" inside the vessels that Schweitzer said could be the nuclei of cells that line the vessel walls or the nuclei of blood cells themselves. Making that determination, however, is "very far down the road," she said.
Horner said the team was lucky that water appeared not to have penetrated the femur, leaving it hollow. Water is the usual way that mineralizing compounds creep into ancient skeletons and fossilize them, replacing the biological material and essentially turning it into rock.
Horner said T. rex thighbones are particularly dense because they supported the entire weight of very large two-legged carnivores, while plant eaters were mostly four-legged. Because of this, he said, the new T. rex was probably "not really unique." He suggested that other researchers would find more soft tissues if they overcome their reluctance to cut up their exhibits.
"Oh, that's right, for sure," said Ohio University's Witmer. "Until now, we never thought we could find something like this, so we never looked. A big part of research is not only knowing what to look for, but also knowing it's there."