Creationists were fascinated, and evolutionists mostly skeptical, when evolutionist Dr Mary Schweitzer claimed in the 1990s that an unfossilized piece of T. rex bone contained red blood cells. Further, that there was immunological and spectroscopic evidence of the presence of hemoglobin, the oxygen-carrying protein that gives red blood cells their colour.
Then in 2005, Schweitzer announced a further sensational discovery in a different T.rex bone. After the mineral matrix was dissolved, what remained were structures with all the appearance of soft tissue, still soft and stretchy. Some of these appeared to be transparent branching blood vessels, with a substance inside them containing further structures looking just like nucleated red blood cells, and able to be squeezed out of the vessels like toothpaste.