An international team led by Curtin University has reported the first unequivocal evidence of fossilized red blood cells and intact heme biomolecules inside the limb bones of a 115-million-year-old theropod dinosaur, *Aratasaurus museunacionali*, recovered in Brazil.

The study, published in Proceedings of the National Academy of Sciences, is described by lead author Kliti Grice as a landmark discovery: while earlier studies suggested possible blood-cell structures in fossils, this is the first to chemically prove hemoglobin-derived molecules inside the cells.

The preserved heme, the oxygen-carrying component of hemoglobin, effectively confirms the remains are fossilized blood.

Paleontologists have long assumed that delicate biomolecules such as hemoglobin could not survive across tens of millions of years, with bones, teeth and eggs carrying nearly all recoverable biological information. The discovery challenges that assumption directly.

According to Discover Magazine, soft tissues like skin, organs and bodily fluids decompose rapidly and rarely preserve, so their loss has long constrained what we can learn about extinct animals.

Finding intact blood-related molecules inside mineralized cells shows that molecular-level preservation can extend far deeper into time than previously believed, opening a direct molecular window onto the physiology of creatures whose skeletons alone tell only part of the story.

The evidence sits in the vascular canals of the fossil bones, where researchers located tiny structures resembling red blood cells alongside heme B and its chemical breakdown products.

phys.org reports that the cells were mineralized with hausmannite, a manganese oxide mineral that acted like a natural time capsule, stabilizing cellular structures and preserving biomolecular components including amino acids of collagen.

Distinguishing genuine biological material from contamination is notoriously difficult, and Discover Magazine notes the team combined imaging and chemical analysis: the blood-cell-like structures were consistently associated with hausmannite, and their molecular signatures differed from the surrounding microbial mat, supporting an origin within the dinosaur's bones.

According to Popular Science, the fossils suggest the juvenile dinosaur measured over ten feet long and weighed about 75 pounds.

The preservation scenario matters as much as the find itself.

The research team, which included scientists from Curtin's School of Earth and Planetary Sciences, the Japan Agency for Marine-Earth Science and Technology, the Brazilian National Museum, the Regional University of Cariri and Johns Hopkins University, believes the exceptional preservation resulted from rapid burial shortly after death in an environment that was simultaneously low in oxygen and rich in microbes.

Those conditions, combined with the mineralizing hausmannite, allowed structures that normally decay within days to persist across geological eras.

The implications stretch beyond paleontology. Grice says the discovery opens new avenues for molecular-level paleontology, allowing researchers to investigate the evolution of blood, dinosaur metabolism and even the activity levels of ancient animals rather than relying solely on skeletons.

According to Martin Van Kranendonk, head of Curtin's School of Earth and Planetary Sciences, the research redefines how molecular structures can survive over long time frames in hostile conditions, with potential implications for astrobiology and the search for ancient life beyond Earth: if such delicate biomolecules can fossilize over millions of years in harsh environments, similar traces of life may linger elsewhere in the universe.

Further study of blood evolution and ancient animal physiology now becomes a concrete research frontier.