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

“Extraordinary claims require extraordinary evidence, and that does require state-of-the-art technology.”

According to sciencenews.org, scientists shared on November 2 in the Proceedings of the National Academy of Sciences that minuscule microstructures discovered inside the limb bones of a 115-million-year-old fossilized specimen represent the leftover traces of red blood cells. The team behind the work states these are both the oldest red blood cell structures yet identified and the first to be chemically proven, though outside researchers have raised questions about the conclusions.

Key Clinical Takeaways:

• Researchers identified ellipse-shaped microstructures inside the fossilized limb bones of Aratasaurus museunacionali, a small feathered theropod dinosaur from 115 million years ago.
• Chemical and imaging analyses revealed that the ellipsoids contained iron, carbon, and nitrogen—components of the biomolecule heme.
• A manganese oxide mineral called hausmannite within the ellipsoid structures may have acted as a natural preservative, entombing the biological material over millions of years.

Analysis of the Mina Pedra Branca Specimen

The fossilized limb bone originated from a site in northeastern Brazil called Mina Pedra Branca and belonged to Aratasaurus museunacionali, a small feathered theropod dinosaur that lived during the Cretaceous Period. Kliti Grice, a paleontologist at Curtin University in Bentley, Australia, and her colleagues used focused electron beams to image thin cross-sectional slices of bone. This revealed ellipse-shaped microstructures nestled within the fossilized network of blood vessels. A chemical composition map showed that these ellipsoids contained iron, carbon, and nitrogen—the core building blocks of heme.

The Preservative Role of Hausmannite

Because blood cells typically decompose within days of an organism’s death, researchers investigated the unusual environmental conditions required to arrest decay during fossilization. In this specific specimen, the team identified a manganese oxide mineral known as hausmannite located directly inside the ellipsoid structures. Grice proposes that hausmannite functioned as a biological time capsule, stabilizing and protecting cellular structures and collagen amino acids from degradation.

This mechanism differs markedly from standard fossilization where mineral-rich fluids simply replace biological tissue after it decays. A notable precedent occurred in a 1997 study when two paleontologists examined tiny spheres inside a pterosaur fossil, initially suspecting ancient blood cells. Those researchers ultimately determined the spheres were pyrite—an iron mineral deposited after death—which established strict criteria for identifying genuine blood cell origins, including shape comparisons with living relatives and biomarker detection.

Experts Question Reliability of Detected Heme Biomarkers

Despite the analytical steps taken by the Curtin University team, other experts remain doubtful. Mary Schweitzer, a paleontologist based at North Carolina State University in Raleigh who did not participate in the recent study, contends that the current data fails to meet established validation standards. Domainfork.com reported that Schweitzer noted the detected heme biomarkers appeared to come from the analysis of the entire bone rather than localizing exclusively to the round structures, as would be expected in authentic fossilized cells. She pointed out that the proposed red blood cells differ in both size and shape from those found in modern birds and reptiles.

Schweitzer’s caution is informed by her own landmark 2005 research, which reported the recovery of flexible, soft-tissue blood vessels from a 68-million-year-old Tyrannosaurus rex leg bone. That discovery ignited long-standing debates regarding the mechanisms of soft-tissue preservation over deep time. In response to these critiques, Grice maintains that her team’s interpretation relies on a robust convergence of anatomy, morphology, mineralogy, elemental analysis, and molecular chemistry, noting that such combined methodology remains essential for evaluating disputed ancient tissues.

Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.