Scientists Find Potential Blood Cells and Heme in 115-Million-Year-Old Dinosaur Fossil

An international team of researchers has identified microscopic structures and chemical signatures resembling red blood cells inside a 115-million-year-old dinosaur fossil found in Brazil. The findings, published in the journal Proceedings of the National Academy of Sciences, offer potential insight into the physiology of extinct animals, challenging long-held assumptions about how long biological molecules can survive.

The fossil belongs to Aratasaurus museunacionali, a carnivorous theropod that grew up to three meters long and lived during the Early Cretaceous period. Paleontologists originally unearthed the rear limb bone in 2008 at the Mina Pedra Branca site in northeastern Brazil's Romualdo Formation, an area renowned for exceptionally well-preserved fossils due to low-oxygen stagnant waters that slowed down decomposition.

Using advanced microscopy and chemical analyses, including mass spectrometry and Raman spectroscopy, the scientists examined the vascular channels of the bone. They discovered numerous oval-shaped microstructures that bore a strong resemblance to red blood cells. Furthermore, the team detected chemical traces of heme, a vital molecule that forms part of hemoglobin, the protein responsible for transporting oxygen throughout the body.

Lead author Kliti Grice, an organic geochemist and distinguished professor at Curtin University in Australia, stated that this is the first time researchers have detected heme in situ within a dinosaur fossil. "We have not found a jar of dinosaur blood," Grice explained. "We have found an extraordinary mineral and molecular echo of its original biology."

The researchers believe that unique environmental conditions following the dinosaur's death contributed to the preservation. They suggest that the animal was covered by a microbial mat in a low-oxygen setting, while minerals such as hausmannita—a manganese oxide—acted as a natural time capsule, stabilizing the cellular structures and biomolecules over millions of years.

Despite the advanced analytical techniques used, the discovery has sparked debate within the scientific community. Mary Schweitzer, a professor emerita at North Carolina State University who did not participate in the study, expressed skepticism regarding whether the structures are genuine fossilized blood cells. She questioned if their size and shape match those of living dinosaur relatives and cast doubt on the role of hausmannita, noting that such manganese oxides are not found in living blood cells. Grice countered that the mineral formed during fossilization and helped preserve the organic material rather than being an original cellular component.

Other experts have also urged caution. Timothy Cleland, a physical scientist at the Smithsonian Institution's Museum Conservation Institute, noted that finding heme does not imply that ancient DNA has survived, as the two molecules fossilize differently. Consequently, this breakthrough does not bring science any closer to the cloning scenarios depicted in fiction like "Jurassic Park."

Nevertheless, researchers hope the new methodology can be applied to other specimens housed in museum collections worldwide. By pushing past the traditional belief that soft tissues and molecular signals cannot endure deep time, scientists may be able to unlock entirely new avenues of research into the metabolism, evolution, and diseases of prehistoric creatures.