Scientists have identified what may be the oldest known traces of dinosaur blood cells inside a 115-million-year-old fossil recovered from Brazil. Researchers at Curtin University in Australia found microscopic structures resembling red blood cells, along with blood-related chemical compounds. The findings could help explain how traces of ancient biological material survive for millions of years.
The fossil belonged to Aratasaurus museunacionali, a small meat-eating dinosaur that lived during the Early Cretaceous period. Brazil has yielded several important prehistoric discoveries, including a giant dinosaur whose fossils revealed ancient connections with Europe.
Chemical evidence supports possible dinosaur blood cell discovery
Researchers examined preserved blood vessel channels inside the dinosaur’s leg bone. They discovered numerous oval-shaped structures similar in size and appearance to red blood cells. However, their appearance alone could not establish their origin. Kliti Grice, an organic geochemist at Curtin University, explained that the team combined microscopic observations with chemical analysis to investigate the structures.
Scientists may have found traces of red blood cells in a dinosaur fossil that is 115 million years old
The discovery was made in Brazil, where researchers also detected chemical traces linked to hemoglobin. Some experts are still questioning whether the structures are really… pic.twitter.com/cXgJ5YNkOO
— Interesting AF (@interesting_aIl) November 3, 2026
Tests found no evidence of fungal growth or certain minerals that might resemble cells. Researchers also detected heme B, a compound associated with hemoglobin, which helps red blood cells carry oxygen. The surrounding rock showed different chemical signatures, strengthening evidence that the material inside the bone came from a distinct source. The findings build on earlier research into dinosaur soft tissues. Scientists previously reported preserved blood vessel structures in a T. rex fossil, raising questions about how biological traces survive fossilization.
How dinosaur blood cell traces survived 115 million years
Researchers believe the fossil’s burial environment helped preserve the delicate structures. The dinosaur’s remains settled in shallow water with extremely low oxygen levels, where microbial mats may have slowed decay. The team suggested that manganese minerals helped preserve the structures during fossilization. Rather than surviving as intact cells, the original biological material likely interacted with surrounding minerals, leaving behind microscopic traces of its shape.
The discovery remains preliminary. Researchers must examine additional fossils and independently confirm the findings before establishing whether the structures are preserved blood cells. Grice said museum collections could provide valuable opportunities for further research. Fossils collected decades ago may contain overlooked chemical evidence that modern techniques can now detect.
Other discoveries, including a 125-million-year-old dinosaur fossil with unusually preserved skin, have also revealed details of ancient dinosaur biology. The study was published in the journal Proceedings of the National Academy of Sciences.
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