WASHINGTON - Researchers have decoded proteins from a 68 million-year-old Tyrannosaurus rex, the oldest such material ever found. The unprecedented step, once thought impossible, adds new weight to the idea that today's birds are descendants of the mighty dinosaurs. "The door just opens up to a whole avenue of research that involves anything extinct," said Matthew T. Carrano, curator of dinosaurs at the Smithsonian's National Museum of Natural History. While dinosaur bones have long been studied, "it's always been assumed that preservation does not extend to the cellular or molecular level," said Mary Higby Schweitzer of North Carolina State University....