Demineralized fragments of tissues line the marrow cavity of a Tyrannosaurus rex femur. Regions of demineralized bone show a fibrous character (indicated by the arrows) that is not normally seen in fossil bone.
A dinosaur bone recently discovered in Montana appears to contain some of the animal's blood vessels and other soft tissues. The bone came from a T. Rex that died some 70 million years ago, and its tissues should be long gone by now. The technique used in this discovery might help find more ancient tissue from long-extinct animals.