In the first analysis of proteins extracted from dinosaur bones, 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 Friday in the journal Science, yielded the first molecular data confirming the widely held hypothesis of a close dinosaur-bird ancestry, the American scientific team reported. The link was previously suggested by anatomical similarities.

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

Similar molecular tests on tissues from the extinct mastodon confirmed its close genetic link to the elephant, as had been suspected from skeletal affinities.