Researchers report preserved red blood cells and heme in 115-million-year-old dinosaur bone

A dinosaur bone with cell-like traces

Researchers led by Kliti Grice of Curtin University in Perth, Australia, describe red blood cell shapes inside bones of Aratasaurus museunacionali, a meat-eating, two-legged dinosaur about 3.1 metres long. The fossils are about 115 million years old and come from northeastern Brazil. The study was published in Proceedings of the National Academy of Sciences (PNAS). The bone that yielded the cells came from a young animal, estimated at about four years old when it died. The cells were found in the channels through which blood vessels once ran.

Chemical signals of blood

Alongside the cell-like shapes, the team reports chemical signals of heme, an iron-containing molecule that binds to haemoglobin, the protein that gives blood its red colour. One account says the team found intact heme-related molecules inside the cells, and the study is described as the first to confirm chemically that haemoglobin-derived molecules survive inside such cells. Grice told Reuters that the team had not found anything resembling a vial of dinosaur blood. She described the results as a mineral and molecular imprint of ancient biology. The researchers also say the work does not document dinosaur DNA.

Why preservation is rare

Soft tissues rarely fossilise, and cells found in bodily fluids such as blood are rarer still, according to the sources. The team attributes the exceptional preservation to rapid burial after death in a low-oxygen setting rich in microorganisms. Since the late 1990s, at least 153 studies have attempted to describe red blood cells in dinosaur bones or other very old fossils. That body of work has long been divided over whether such material can survive.

Scepticism and reactions

Independent researchers who commented in Science did not challenge the study's methodology, but they expressed reservations. They noted that the traces are longer and wider than red blood cells of crocodiles and birds, the closest living relatives of dinosaurs. Martin Van Kranendonk, head of the School of Earth and Planetary Sciences at Curtin, said the findings could change how molecular structures are preserved over long periods or in harsh conditions. Grice said the discovery offers a direct molecular window into the physiology of long-extinct animals and the environments they lived in.