Examining the stony material with computerized imaging technology, scientists came upon an even bigger surprise, one that could profoundly change theories of dinosaur physiology and the place of at least some of these creatures in the evolutionary history of life. Visible traces of the heart's internal structure revealed, the discoverers said, that the organ was more like the heart of a bird or mammal than any known reptile.
''It's truly amazing that this animal seems to have had such a highly evolved heart,'' Dr. Dale A. Russell of the North Carolina Museum of Natural Sciences in Raleigh said in announcing the discovery. ''The implications completely floored me.''