Alive as dinosaurs may seem to children, knowledge of them as living creatures is limited almost entirely to what can be learned from bones that have long since turned to stony fossils. Their soft tissues, when rarely recovered, have lost their original revealing form. A 70-million-year-old Tyrannosaurus rex recently discovered in Montana, scientists reported today, has apparently yielded the improbable: soft tissues, including blood vessels and possibly cells, that "retain some of their original flexibility, elasticity and resilience." In a paper being published on Friday in the journal Science, the discovery team said that the remarkable preservation of the tissue...