Protein scraps help fill in dino family tree

WASHINGTON (Reuters) - Scraps of protein from the bones of a 68 million-year-old dinosaur and a mastodon carcass confirm their places in the family tree of life on Earth, researchers reported on Thursday.

The same team that established Tyrannosaurus rex is a distant relative of chickens filled in more gaps, showing that the dinosaur was far more closely related to living birds than to alligators.

And a 500,000-year-old mastodon is clearly a close relative of elephants, John Asara and colleagues at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston reported.

They said their analysis of the ancient preserved proteins can be used to fill in all sorts of gaps in the tree of evolution. But it also shows that classical methods, based on studying an animal's bones and other physical structures, are accurate.

"If you ... just use molecular data, you can come to the same conclusion," Asara said in a telephone interview.

Asara's team used collagen taken from a remarkable find -- the leg bone of a T. rex sealed in stone and broken when researchers had no other way of removing it.

Mary Schweitzer of North Carolina State University was able to get soft tissue and then protein out of the bone in 2005 -- something previously considered impossible. She also got protein out of the much younger mastodon bone.

Asara's team looked at the protein on a molecular level and designed a computer program to analyze it. A year ago, they established that the Tyrannosaurus was related to modern chickens and ostriches and that the mastodon was related to living mammals.

T. REX AND BIRDS

Now, reporting in the journal Science, they said they have established that the dinosaur is more similar to birds than to alligators or other reptiles such as anole lizards.

"Last year we just made a very loose connection based on (protein) sequence identification and we had no reptiles," Asara said. "And now with very high probability we can make the connection of T. rex to birds."

The mastodon "groups very nicely with elephants," he said. "We can get a very nice tree."

Some of the computer programs take days to run, Asara noted. But they will keep seeking fresh samples from paleontologists.

"You can't just grab things from museums," Asara said, because the protein in them will have degraded.

Last September, a researcher at Pennsylvania State University reported his team had pulled DNA from the hair shafts of Siberian woolly mammoths that were 50,000 years old.

Separately on Thursday, scientists at the University of California, Berkeley said they had used new rock dating methods to pinpoint the extinction of the dinosaurs more precisely than ever before.

Their improved argon-argon dating method places the Cretaceous-Tertiary, or K/T, boundary at 65.95 million years ago, give or take 40,000 years. Earlier estimates had put it at 65.5 million years ago, with a 300,000-year margin of error.

(Editing by Xavier Briand)