Curtin team reports blood-cell traces in 115-million-year-old dinosaur bone

What the team reported

The paper reports mineralised red blood cell-like structures and heme biomolecules in the hind-limb bones of Aratasaurus museunacionali, a small theropod from northeastern Brazil. The animal was a juvenile, estimated at about 3.12 metres long and 34 kilograms, roughly four years old at death and possibly still growing. The fossil is about 115 million years old, from the Romualdo Formation in Ceará state.

The structures average about 23 micrometres long and 20 micrometres wide.

They sit inside vascular canals, the narrow channels that once carried blood vessels through the bone, and that location carries much of the argument: in living vertebrates, red blood cells occupy the same space. Chemical analysis found heme B, the iron-bearing part of haemoglobin, and a derivative called 3,8-diethyl heme B. The team combined microscopy, elemental mapping, spectroscopy and high-performance liquid chromatography-mass spectrometry, and reported iron, carbon and nitrogen associated with the structures. The authors describe the result as the first chemical proof of haemoglobin-derived molecules inside mineralised fossil cells.

The team included researchers from Curtin's School of Earth and Planetary Sciences, the Japan Agency for Marine-Earth Science and Technology, the Brazilian National Museum, the Regional University of Cariri and Johns Hopkins University.

Why it matters

The claim extends the known fossil record of blood to 115 million years.

If it holds, it gives researchers a molecular route into dinosaur physiology, including blood evolution, metabolism and activity levels. It does not deliver a vial of dinosaur blood. The team found no liquid blood, no intact haemoglobin protein and no DNA. The practical effect is narrower: knowing this preservation is possible tells other teams what to look for in unusually well-preserved bone, and how to test whether a cell-shaped blob really carries animal chemistry.

The animal lived during the Early Cretaceous. Curtin also points outward, arguing that if delicate biomolecules can fossilise over millions of years, similar traces of life might persist elsewhere in the universe.

How the traces survived

The team's explanation starts with burial: rapid sediment cover in a low-oxygen, microbially rich setting that would have slowed normal decay.

A manganese oxide mineral, hausmannite, mineralised the cell-like structures. Grice has described it as a natural time capsule that stabilised the structures and their contents before they could break down. The sediment around the bone told a different chemical story, mostly plant and bacterial compounds, which the authors say makes contamination from the rock less likely. The bone also yielded amino acids associated with collagen, the main structural protein in connective tissue.

The specimen has its own history. Workers found it in a gypsum mine in 2008, and it was later held at the National Museum of Brazil in Rio de Janeiro. A fire destroyed much of that museum's collection in September 2018, but the building holding this fossil was not affected.

Its genus name means "lizard born from fire", a reference to the museum fire the fossil survived.

The dispute and what remains open

Not everyone accepts the identification. Mary Schweitzer, a molecular palaeontologist at North Carolina State University, is not convinced the structures are red blood cells.

Her objection is morphological. Birds and reptiles keep the nuclei in their red blood cells, which usually gives the cell a bulge, and Schweitzer says the Aratasaurus structures are concave, show no such bulge and are smaller than most nonmammalian red blood cells. She was more persuaded by the heme and collagen amino acid results, and said there was much to learn from exceptionally well-preserved fossils. Schweitzer has studied soft tissues from the dinosaur age for years and agrees that molecules made inside an animal can persist over geological time.

Grice has said museum collections may hold overlooked chemical evidence that modern techniques can now detect.

What would settle it is replication: the same chemistry, found in situ, in another specimen.