Scientists have discovered fossilized red blood cells inside a dinosaur bone dating back approximately 115 million years. This discovery, made in Brazil, could provide a rare opportunity to study soft tissue traces in ancient animals.
A research team led by scientists from Curtin University in Australia studied a leg bone belonging to Aratasaurus museunacionali, a small theropod that lived approximately 115 million years ago, according to Science Alert.
The fossil was discovered in a Brazilian mine in 2008. Within the tiny channels through which blood once flowed, the researchers observed numerous small oval structures resembling cells.
Similar claims have been made before: researchers have reported finding proteins or cell-like material in dinosaur fossils. However, such findings were often difficult to reproduce, and it wasn't always possible to rule out the possibility of contamination entering the bones after the animals' death.
This time, the team combined microscopic observations with several types of chemical analysis. "What looks like a blood cell under the microscope is interesting, but morphology alone isn't enough to establish its biological origin," noted Clytie Grice, an organic geochemist at Curtin University. She explained that the researchers also looked for chemical evidence associated with these structures.
Photo: Scientists combined microscopic observations with several types of chemical analysis
The team considered the possibility that the findings were the result of fungi or microorganisms growing on the bones before they fossilized. Such organisms typically leave traces such as filaments, spores, or biofilms, but the researchers found no evidence of their presence. The analysis also revealed no pyrite or sediment grains that could be mistaken for cells.
At the same time, chemical analysis revealed heme B, a molecule associated with blood and essential for oxygen transport in blood. The substance found in the bone had a different chemical composition than the surrounding rock.
Elemental analysis provided another clue: the cellular structures contained iron, carbon, and nitrogen—elements that can be found in heme. Other parts of the bone had a different composition, specifically phosphorus, calcium, and fluorine.
If confirmed, these structures would be the oldest known dinosaur blood cells. Previously described samples were dated to no more than approximately 80 million years old.
Researchers believe the unusual conditions under which the animal was buried explain how such fragile traces were preserved. The bone was preserved in a microbial mat in shallow water, where oxygen was virtually absent.
Photo: The unusual conditions under which the animal was buried explain how such fragile traces were preserved
Grice noted that manganese minerals likely helped stabilize or restore the contours of the original structures during fossilization. This does not mean that the unaltered blood cells remained intact for 115 million years. Instead, the minerals and the surrounding environment likely preserved the chemical and structural information of tissue, which typically decomposes quickly.
The team emphasized that further research is needed. "The top priority is replicating the results," Grice explained. The researchers will test other fossils from different geological environments and different dinosaur groups using independent methods. Replicating the results will help establish whether the chemical signatures truly indicate ancient blood-related material.
This discovery may encourage museums and universities to reexamine fossils already in their collections. Grice noted that samples collected decades ago may contain microscopic, chemical, or mineral evidence that researchers did not have the opportunity or reason to study at the time.
