Dinosaur Fossil Yields Chemical Traces Linked to Blood

The fossilized hind leg belonged to Aratasaurus museunacionali, a predator that roamed during the Cretaceous Period. Researchers examined thin slices of the bone using imaging and chemical tests, finding elliptical structures inside its network of blood vessels.

The structures contained iron, carbon and nitrogen. Further analyses indicated porphyrins, compounds associated with blood and involved in forming heme, a component of hemoglobin. The researchers say the combined evidence points to preserved molecular remnants of ancient blood alongside mineralized shapes resembling red blood cells.

They also identified hausmannite, a manganese oxide mineral, within the structures. The team proposes it helped shield cellular forms and molecules from decay during fossilization. The researchers say the specimen may offer a way to seek similar traces in other fossils and museum collections.

The interpretation remains contested. Paleontologist Mary Schweitzer, who was not involved in the study, said the heme-related evidence was measured across the bone rather than specifically within the rounded structures. She also noted that the structures differ in size and shape from blood cells in living birds and reptiles.

Lead researcher Kliti Grice said the conclusion draws on several kinds of evidence, including the structures’ location and the chemical and mineral findings. The study did not identify liquid blood, intact hemoglobin or preserved DNA. The researchers propose examining other fossils with potentially favorable preservation using microscopy and chemical techniques.