115-Million-Year-Old Dinosaur Bone From Brazil Holds Traces of Blood Molecules

An international team says it has found chemical traces of blood inside a 115-million-year-old dinosaur bone from Brazil. The researchers report mineralized structures that look like red blood cells and molecules from hemoglobin, the oxygen-carrying protein in blood. If the interpretation holds, it suggests that fragile biological material can survive far longer than many scientists assumed.

The work, led by Curtin University, was published in the Proceedings of the National Academy of Sciences. According to the team, it is the first direct molecular evidence of blood-derived compounds preserved inside structures resembling red blood cells in a dinosaur fossil.

What the researchers found in the fossil

The specimen is a partial hind limb of Aratasaurus museunacionali, a small meat-eating theropod dinosaur from the Romualdo Formation in northeast Brazil. The formation is known for finely preserved fossils of fish, turtles, crocodile relatives and pterosaurs, according to EarthSky, which published an account written by the study's lead scientist, Kliti Grice of Curtin University.

Inside the limb bone, the team found numerous mineralized structures resembling red blood cells in vascular canals, the tiny channels that once held blood vessels. Chemical analysis detected heme molecules, a component of hemoglobin. The team also reported amino acids associated with collagen, a structural protein in bones and connective tissue.

The fossil is also notable for its history. It was part of Brazil's National Museum collection until a fire in 2018 destroyed much of the museum's holdings, though the building that held this fossil was not affected. The genus name combines Tupi and Greek words and, together with the species name, means “the dinosaur born from the National Museum fire,” Grice wrote.

How the team tested whether it is really blood

A central question was whether the structures were true biological remains or something that formed later as the bone turned to stone. Grice wrote that the structures appear only within the vascular canals, where red blood cells sit in living vertebrates. The surrounding sediment contained none of them, which makes outside contamination less likely, she said.

The chemistry also differed sharply. The sediment mostly held compounds from plants and bacteria, while the bone showed a distinct signature dominated by heme molecules. The team reported two chemical fingerprints of blood, and other techniques confirmed heme along with iron, carbon and nitrogen. Grice said evidence from microscopy, mineralogy, spectroscopy and molecular geochemistry all pointed the same way, and that the team ruled out several alternative explanations.

How blood might last 115 million years

The researchers suspect the dinosaur was buried quickly in an environment with little oxygen and abundant microbial activity, which slowed decay. Grice stressed that the blood did not stay fresh: the cells turned into minerals during fossilization.

A mineral called hausmannite may also have helped. The team says it can act somewhat like an antioxidant, stabilizing sensitive organic molecules and slowing their breakdown. ScienceDaily, which published Curtin's news release, described the mineral as a natural time capsule. These preservation factors are the team's proposed explanation rather than something proven.

An open question about cell shape

The fossil cell-like structures look somewhat larger and more rounded than red blood cells in modern birds and crocodilians. Grice wrote that this could be distortion during fossilization, or it could mean the red blood cells of dinosaurs not closely related to birds had a different shape. She said further research is needed to settle the question.

Why it matters beyond one dinosaur

The finding challenges a long-held view in paleontology that hemoglobin-derived molecules could not last across such spans of time. Grice called it a landmark discovery. She said it could open the way to studying the evolution of blood, metabolism and even activity levels in extinct animals, details that are hard to read from bones alone.

The researchers also say other fossils, including those already in museum collections, may hold molecular information that routine examination has missed. Martin Van Kranendonk, head of Curtin's School of Earth and Planetary Sciences, said the results are changing how scientists view the preservation of molecular structures over vast timescales.

The team also points to astrobiology, the study of possible life beyond Earth. If biological molecules can persist for more than 100 million years under the right conditions, scientists may need to rethink where and how they search for traces of ancient organisms, according to ScienceDaily. That is a possibility the researchers raise, not a demonstrated result.

Both accounts come from the study team and Curtin University, and this is a single study. Its conclusions rest on the team's interpretation of the evidence.

Researchers from Curtin, the Japan Agency for Marine-Earth Science and Technology, the Brazilian National Museum, the Regional University of Cariri and Johns Hopkins University took part.

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Around Prague, based on reporting by ScienceDaily, EarthSky