The fossilized remains belong to Aratasaurus museunacionali, a species of coelurosaurian theropod dinosaur that lived in what is now northeastern Brazil during the Early Cretaceous epoch, some 115 million years ago.
SEM images showing red blood cell-like structures in the bone of Aratasaurus museunacionali. Image credit: Grice et al., doi: 10.1073/pnas.2614248123.
“Our findings challenge longstanding assumptions that certain biomolecules such as hemoglobin cannot survive deep time,” said Curtin University’s Professor Kliti Grice, first author of the study.
“It opens exciting new avenues for molecular-level paleontology, allowing us to investigate the evolution of blood, metabolism and even activity levels in ancient animals.”
In the study, Professor Grice and colleagues examined Aratasaurus museunacionali’s hind-limb bones.
The fossils came from the Mina Pedra Branca site of the Romualdo Formation, which is known worldwide for the large number of well-preserved specimens.
The paleontologists identified numerous tiny, ellipsoidal structures inside the bones’ vascular canals, the channels that once carried blood vessels.
The structures average about 23 micrometers in length and 20 micrometers in width.
Life reconstruction of Aratasaurus museunacionali. Image credit: Maurilio Oliveira.
The researchers detected heme B, a molecule central to the oxygen-carrying function of hemoglobin, along with a chemically altered derivative known as 3,8-diethyl heme B.
Further imaging and spectroscopic analyses located heme-related chemical signatures within the same structures, strengthening the interpretation that they are mineralized remnants of red blood cells.
The scientists suggest that manganese oxide mineralization, particularly a mineral called hausmannite, helped protect the cellular structures and their organic contents from degradation.
The discovery does not mean that intact blood or hemoglobin proteins survived for more than 100 million years.
“To detect intact heme derived molecules in 115-million-year-old red blood cells is astonishing: this really is a landmark discovery,” Professor Grice said.
“It not only extends the known fossil record of blood, but also offers a direct molecular window into the physiology of long-extinct animals so we may better understand them and the world they lived in.”
A paper on the findings was published today in the Proceedings of the National Academy of Sciences.
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Kliti Grice et al. 2026. Heme signatures in mineralized red blood cells within vascular canals of a 115-million-year-old dinosaur bone. PNAS 123 (46): e2614248123; doi: 10.1073/pnas.2614248123
