Fossilized hind-limb bones of Aratasaurus museunasionali, a coelurosaurian theropod that lived in what is now northeastern Brazil about 115 million years ago during the Early Cretaceous, contain structures interpreted as calcified red blood cells. Chemical analyses detected heme-related molecules within the structures, suggesting that mineralization helped preserve molecular evidence of the dinosaur’s blood.
“Our findings challenge the long-held assumption that certain biomolecules, such as hemoglobin, cannot survive for long periods of time,” said Curtin University’s Professor Kriti Grice, the study’s lead author.
“This opens up exciting new avenues in molecular paleontology, allowing us to investigate the evolution of blood, metabolism, and even activity levels in ancient animals.”
Blood-cell-like structures in dinosaur bone
Grice and her colleagues examined hind-limb bones of Aratasaurus museunasionali. The fossil was excavated at the Mina Pedra Blanca site in Brazil’s Romualdo Formation, which is known for its large number of well-preserved specimens.
The researchers identified numerous small, oval structures inside the bone’s vascular canals—the channels through which blood vessels once passed. The structures measure approximately 23 micrometers in length and 20 micrometers in width.
Further imaging and spectroscopic analyses detected chemical signatures associated with heme B, the molecule central to hemoglobin’s oxygen-carrying function. The researchers also identified 3,8-diethylheme B, a chemically modified derivative of heme B.
These findings support the interpretation that the structures are mineralized remains of red blood cells rather than unrelated mineral formations.
Mineralization may have aided preservation
The scientists suggest that mineralization by manganese oxides, particularly the mineral hausmannite, helped protect the cell structures and their organic contents from deterioration.
However, the discovery does not mean that intact blood or hemoglobin proteins survived for more than 100 million years. Instead, the analyses detected heme-derived molecules and chemical signatures preserved within the mineralized structures.
“It’s amazing that we detected intact heme-derived molecules in 115-million-year-old red blood cells. This is a truly groundbreaking discovery,” Grice said.
“This not only expands the known blood fossil record, but also provides a direct molecular window into the physiology of long-extinct animals, potentially allowing us to better understand animals and the world they lived in.”
The study was published in Proceedings of the National Academy of Sciences.
Grice et al. 2026. “Heme signature of calcified red blood cells in blood vessels of a 115-million-year-old dinosaur bone.” PNAS 123 (46): e2614248123. doi:10.1073/pnas.2614248123.
Source: www.sci.news
