Molecules never before observed survived 68 million years in that goo, Harvard University scientists revealed Thursday. The discovery of protein fragments breaks open a new way to research extinct animals and fill in blanks on the tree of life.

Already, the breakthrough has yielded a payoff. Schweitzer and the Harvard scientists found molecular similarities between the Tyrannosaurus rex and modern chickens. They say the finding strengthens a growing case that birds are living relatives of dinosaurs.

More tests are needed to see whether the bits of dinosaur proteins match those in other living creatures -- including alligators and crocodiles, which, by outward appearances, seem closely related to the ancient species. Molecular maps of proteins in those reptiles are not yet available.

"Potential studies include verifying and clarifying relationships between extinct and living organisms and between extinct and extinct," Schweitzer said. "That's just for starters."

Using an ultrasensitive instrument, Harvard chemist John Asara identified seven protein fragments from what Schweitzer thinks is collagen tissue she found in the T. rex. Now Asara is preparing to look for proteins in the T. rex remains that resemble blood vessels and blood cells, he said.

Stunning preservation

The very existence of the molecular relics had been unimaginable. Until now, scientists thought such soft stuff survived no more than a million years in animal remains. Usually, tissue degrades and bone gets replaced by mineral, yielding fossils molded precisely like the originals. Although the fossils enable scientists to piece together a skeletal sketch of ancient life forms, they tell only so much.

The discovery of the protein fragments, detailed in the journal Science today, suggests that new molecular clues may be buried in other well-preserved fossils around the world. And those clues could help explain the biology of dinosaurs and other extinct animals.

The newly discovered microscopic fragments are not DNA -- the inherited code stored in billions of cells that defines every living creature. As a result, no one should expect any Jurassic Park-like replicas of dinosaurs to result from Schweitzer's finding.

But researchers are close. Proteins, direct products of DNA, perform countless tasks in cells. Scientists increasingly study differences in the components of proteins to discern differences between whole organisms.

Jack Horner, a prominent Montana paleontologist and Schweitzer's mentor, predicted that the success of the T. rex discovery will encourage scientists to look for better-preserved fossils in more remote regions.

"One of the most important things to come out of all this is how it's going to change the way that people like myself go out and collect data," Horner said. "To get specimens like that requires excavating enormous amounts of materials first."

A mentor's gift

In 2002, Horner dug the T. rex out of a remote cliff face in the Hell Creek formation that covers parts of Montana and Wyoming. He gave the femur bone to Schweitzer, a former student, because of her expertise in looking for molecular remains in fossils.

This summer, with private funding, Horner is dispatching teams to look for similar opportunities -- fossils buried deeper than most but exposed on cliff sides -- in Wyoming, China and elsewhere.

Them bones

There is no guarantee that these expeditions will succeed, said paleontologist Hans-Dieter Sues, research and collections associate director at the National Museum of Natural History. But there is new reason to look.

"This is another fascinating discovery by Mary Schweitzer, who has become a veritable pioneer in the area of molecular paleontology. It remains to be seen whether there are other fossil occurrences that have this remarkable kind of molecular preservation."

Schweitzer, a paleontology curator at the N.C. Museum of Natural Sciences, rocked her field of study twice in 2005. First she found the soft tissue in the T. rex bone.

Then she identified a thin layer of bone tissue in the fossil.

It resembles the coating that primitive birds produce as a calcium source before they lay eggs.

Schweitzer said not all paleontologists will want to put their fossils in her hands, even if they discover a promising one. To look for what she studies, she said, she needs to damage fossils to look for tissue remains.

"Most curators don't like me," Schweitzer said. "This is a destructive approach to research. But with the amount of information we gain, it's probably worth it."