Giving flight to dinosaur-bird links

Study offers new proof, redraws major family tree

A Harvard study offers new evidence that the awe-inspiring Tyrannosaurus Rex, catching a youngster's eye at an Earth Day event in Idaho, has relatives among the flocks of modern birds. (Barry Kough/ASSOCIATED PRESS)

NEW YORK - In the first analysis of proteins extracted from dinosaur bones, Harvard-affiliated scientists say they have established more firmly than ever that the closest living relatives of the mighty predator Tyrannosaurus rex are modern birds.

The research, being published today in the journal Science, yielded the first molecular data confirming the widely held hypothesis of a close dinosaur-bird ancestry, the research team reported. The link was previously suggested by anatomical similarities.

The scientists said they found T. rex shared more of its genetic makeup with ostriches and chickens than with living reptiles, like alligators. On this basis, the team has redrawn the family tree of major vertebrate groups, assigning the dinosaur a new place in evolutionary relationships.

"Our results at the genetic level basically agree with what has been seen in skeletal data," John Asara of Harvard said in a phone interview. "There is more than a 90 percent probability that the grouping of T. rex with living birds is real."

Asara and Lewis Cantley, both of Beth Israel Deaconess Medical Center in Boston and Harvard Medical School, processed the proteins from tissue recovered deep in bones of a 68 million-year-old T. rex excavated in 2003 by John Horner of Montana State University. Mary Schweitzer of North Carolina State University discovered the preserved soft tissues.

For the molecular study, Asara and Chris Organ, a researcher in evolutionary biology at Harvard and the report's lead author, compared the dinosaur protein with similar protein from several dozen species of modern birds, reptiles, and other animals. The researchers said they planned to study more species of birds, reptiles, and other dinosaurs.

Paleontologists were not surprised by the findings. An accumulation of fossil evidence in recent years had increased their confidence that birds descended from certain dinosaurs - or, as they sometimes put it, that birds are living dinosaurs.