Fossilized Red Blood Cells Found in 115-Million-Year-Old Dinosaur Bone

Scientists have found what they consider the strongest evidence yet of red blood cells in a dinosaur fossil, discovered in the right leg bone of a medium-sized dinosaur that lived in Brazil about 115 million years ago during the Cretaceous period. Researchers identified microscopic structures in the fossil of the dinosaur species Aratasaurus museunacionali that appear to be fossilized red blood cells, along with chemical evidence of heme, an iron-containing molecule linked to hemoglobin that gives blood its red color. The cells and heme were found in vascular canals of a young dinosaur estimated to be about four years old at death, measuring roughly 3.1 meters long. The study, published Monday in the journal Proceedings of the National Academy of Sciences, was led by geochemist Cleide Grace of Curtin University in Australia, who noted the findings represent "a metallic and molecular echo of ancient biology" rather than preserved dinosaur blood. The researchers also found amino acids linked to collagen but emphasized the discovery does not document dinosaur DNA or intact ancient proteins, with co-author Alexander Kellner of the Brazilian National Museum noting the fossil was found in a gypsum mine in Ceará state.