In 2005 the unexpected occurred; researchers reported what appeared to be preserved soft tissues inside the femur of a Tyrannosaurus rex excavated from the Hell Creek Formation. Structures that looked like blood vessels and blood cells were seen under the microscope, and although it is still unknown whether this is original organic material or material that has somehow been preserved the structures provided some tantalizing clues. What the researchers have been more confident about, however, is that they were able to detect the presence of preserved collagen proteins in the material. (Indeed, research carried out in 1999 on the remnants of feathers of Shuvuuviathe remnants of feathers of Shuvuuvia illustrated that proteins have the potential to survive over