An international team led by Curtin University found heme-derived molecules and mineralized red blood cell structures in the bones of Aratasaurus museunacionali, a 115-million-year-old theropod dinosaur from Brazil.
Scientists have found chemically confirmed traces of ancient blood inside 115-million-year-old dinosaur bones, according to research published in the Proceedings of the National Academy of Sciences.
An international team led by Curtin University examined the limb bones of Aratasaurus museunacionali, a meat-eating theropod dinosaur discovered in northeastern Brazil. The researchers identified numerous mineralized red blood cells inside vascular canals, the tiny passages that once contained blood vessels.
Chemical analysis revealed preserved heme molecules, which are components of hemoglobin, the protein that allows red blood cells to transport oxygen. The team also found amino acids associated with collagen, an important structural protein found in bones and other connective tissues.
"To detect intact heme-derived molecules in 115-million-year-old red blood cells is astonishing: this really is a landmark discovery," Professor Kliti Grice said.
The extraordinary preservation appears to be connected to a mineral called hausmannite. This mineral helped stabilize the fossilized blood cells and preserve their molecular components over an immense span of geological time.
Researchers believe the conditions surrounding the dinosaur's burial were also crucial. They suspect the animal was quickly covered by sediment in an environment with little oxygen and abundant microbial activity. These conditions may have helped preserve biological material that would ordinarily have broken down and disappeared.
The study's authors say the findings open new avenues for molecular-level paleontology. "It opens exciting new avenues for molecular-level palaeontology, allowing us to investigate the evolution of blood, metabolism and even activity levels in ancient animals," Professor Grice said.
However, not all experts are convinced the structures are blood cells. Mary Schweitzer, an emeritus professor at North Carolina State University, told ABC Australia she found the blood-cell evidence unconvincing. "I have no problem with the presence of heme and collagen in the bone matrix," she said, while praising the authors for using multiple methods. Her objection is size: one of the imaged structures measured roughly 15 microns, which she noted is smaller than nearly all red blood cells of non-mammals.
Mauricio Barbi of the University of Regina, also not involved in the work, called the evidence convincing for mineralized structures consistent with red blood cells. He added that identifying them still involves interpretation, since what survives are chemical remnants and mineral structures rather than intact cells or hemoglobin.
Earlier research has also reported blood-related chemistry in dinosaur fossils. A 1997 study reported evidence for heme-containing compounds or hemoglobin breakdown products in Tyrannosaurus rex bone extracts. A 2025 study used resonance Raman methods to investigate partial hemoglobin preservation in dinosaur remains.
The discovery demonstrates that some biological materials once thought too fragile to survive for millions of years can remain detectable under exceptional conditions. The research team included scientists from Curtin University'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. The study was supported by a 2021 Australian Research Council Laureate Fellowship awarded to Professor Grice.
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