The discovery of traces of flesh in a 68-million-year-old Tyrannosaurus rex bone ties the King of the Dinosaurs to modern-day species and, scientists say, heralds a "milestone" shift in paleontology.

"Based on the small sample we've recovered, chickens may be the closest relatives (to T. rex)," says geneticist John Asara of Beth Israel Deaconess Medical Center in Boston, co-leader of a team reporting the discovery of faint traces of chicken-like bone lining preserved inside a dinosaur drumstick.

In studies reported in the journal Science, Asara and colleagues conclude that seven traces of proteins detected in purified T. rex bone most closely match those reported in chickens, followed by frogs and newts.

The astonishing find of barely detectable tissue from a creature tens of millions of years old, along with similar traces the team found in a mastodon bone at least 160,000 years old, upends the conventional view of fossils and may shift paleontologists' focus from bone hunting to biochemistry, say experts.

Until now, scientists thought fossilization replaced every last bit of living tissue with inert mineral.

"I'd call it a milestone," says paleontologist Hans Larsson of McGill University in Montreal, who was not part of the studies. "Dinosaurs will enter the field of molecular biology and really slingshot paleontology into the modern world."

In the two studies, led by Asara and Mary Schweitzer of North Carolina State University in Raleigh, the team unearthed a T. rex buried underneath 60 feet of cliffside rock in Hell Creek, Mont.

Keeping the dinosaur entombed in sandstone to prevent contamination, the scientists extracted a few grams of material from its thick thighbone, and forwarded the bone powder to Asara's lab. There it was ground down to about a billionth of a gram of material, suitable for inspection with a high-tech mass spectrometer generally used to precisely diagnose cancer genes inside tumors.

The team suspects the dry sandstone, combined with the thickness of the T. rex bone, allowed some faint measure of preservation, only about 1% of the purified sample's collagen, the ribbonlike tissue found in ligaments, tendons and bone lining inside the thighbone.

The protein traces are a far cry from the Jurassic Park vision of genes leading to a re-created dinosaur, Larsson notes. He voiced some caution about the results until independent researchers have ruled out the possibility of contamination in the bone samples.

"It wasn't terribly long ago we thought there was no preservation whatsoever in fossils," says paleontologist Thomas Holtz of the University of Maryland in College Park. "We have a lot more to learn about fossilization."

"Finding any soft tissues in dinosaur bones greatly surprised us," says Schweitzer, who led a 2005 study that found still-elastic blood vessel remains in a dinosaur bone. Her team plans to embark on a worldwide exploration of dinosaur sites in the next year, looking for more fossil bones to examine.

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