Fossil, Mary Schweitzer | featured news

Twenty years ago, paleontologist Mary Schweitzer made an astonishing discovery. Peering through a microscope at a slice of dinosaur bone, she spotted what looked for all the world like red blood cells. It seemed utterly impossible—organic remains were not supposed to survive the fossilization process—but test after test indicated that the spherical structures were indeed red blood cells from a 67-million-year-old Tyrannosaurus rex. In the years that followed, she and her colleagues discovered other apparent soft tissues, including what seem to be blood vessels and feather fibers. But controversy accompanied their claims. Skeptics argued that the alleged organic tissues were instead biofilm—slime formed by microbes that invaded the fossilized bone.