Are they red blood cells that scientists found inside the bones of this dinosaur?

Dinosaur fossils may hold unprecedented evidence about their biology, but finding traces of their blood has remained extremely difficult. However, researchers say that they have found in a dinosaur bone dating back 115 million years, the strongest evidence yet of the presence of red blood cells preserved inside a fossil.

Tissues, cells and other soft biological materials rarely survive the fossilization process, making their discovery a matter of scientific controversy. Although studies since the late 1990s have observed structures resembling red blood cells in fossils of dinosaurs and other reptiles, the validity of these results has remained a matter of controversy among researchers.

In the new study, published in the Proceedings of the National Academy of Sciences on Monday, researchers combined microscopic imaging techniques and chemical analysis, and observed oval microscopic structures resembling red blood cells, along with chemical evidence of the presence of heme, a molecule involved in the formation of hemoglobin, the protein responsible for transporting oxygen in red blood cells. According to the study's authors, this is the first time that heme has been observed within the same structures in a dinosaur fossil.

The lead author of the study, Keleti Grace, an organic geochemist and distinguished professor at Curtin University in Perth, Australia, told Ofoq News that the well-preserved bone dating back to the Early Cretaceous period, along with the research method used, enhances the possibility of the survival of biological structures and molecules within ancient fossils. She added: "The importance of the discovery is not limited only to what we found inside this dinosaur, but also that we now have methods that can be applied to other fossils to determine how much original biological information may still be preserved within them."

However, this discovery does not meet the consensus of experts, as some of them still doubt whether the discovered structures are actually red blood cells. Grace believes that finding similar evidence in other fossils may allow researchers to ask “much more advanced questions about the physiology of extinct animals.”

Evidence inside a dinosaur bone The fossil belongs to part of the hind limb of Aratasaurus museunacionali, a theropod dinosaur that lived during the Early Cretaceous period. Paleontologists extracted the tibia in 2008 from the Mina Pedra Branca site in northeastern Brazil, within the Romualdo geological formation known for its exceptionally preserved fossils.

Scientists believe that stagnant water in the area limited the availability of oxygen and slowed the decomposition of the remains buried there. Within the vascular canals of the bone, which are microscopic tubes that contain blood vessels and nerve fibers, researchers found large numbers of oval-shaped structures that resemble red blood cells.

They then used imaging techniques and chemical analysis to verify their properties. Grace explains that previous studies examined, separately, structures similar to red blood cells and possible chemical traces of blood components in dinosaur fossils, but the new study gathered multiple pieces of evidence, including: The researchers suggest that low oxygen levels in the burial environment limited the decomposition of organic materials, which helped the survival of these structures.

They also detected traces of manganese oxides inside the bone, and they believe that these minerals may have contributed to its stabilization and preservation. “Bones provide extraordinary information about anatomy, growth, movement and development,” Grace said.

“But preserving cells and molecules gives us access to a different level of biological information, about the chemistry and tissues of the organism when it was alive.” However, she stressed that it is too early to draw conclusions about the physiology of Aratasaurus based on a single specimen.

She added: "One of the first questions we need to answer is whether this discovery is very rare, or whether similar cases have simply not been observed in other fossils. There may be fossils preserved in museums around the world that contain molecular and cellular information that has not previously been examined."

New horizons, disputed evidence Grace and her team intend to expand their research to include fossils of different species, dating back to multiple geological periods and found in diverse environments, to find out how widespread this type of preserved molecular evidence is. These discoveries may help in the future to understand how dinosaurs transported oxygen within their bodies, how their tissues worked, and how their biology differed from animals living today.

But will finding dinosaur red blood cells bring scientists closer to recreating its DNA, as in books and movies like “Jurassic Park”? Not necessarily, says Timothy Kland, a physicist at the Smithsonian's Collections Conservation Institute who was not involved in the study.

Kland explained that heme and DNA are two different molecules, and each fossilizes differently inside bones, so finding evidence that one survived does not necessarily mean that the other survived as well. “This study opens new research horizons to explore how heme B remains inside bones, especially in exceptional sites like this one,” Kland noted.

Heme B is the most common form of heme. He added that the study raises the question of whether similar evidence can be found in other species within the Romualdo Formation, or in other sites characterized by exceptional preservation conditions.

On the other hand, the study authors pointed out that the discovered structures differ in size and shape from the red blood cells of modern birds and crocodiles. But they cautioned that these species may not be the most appropriate reference for comparing them to non-avian dinosaurs, as well as the possibility that the cells may have lost their original shape after the animal's death.

Kland believes that future research may help understand the changes that occur in red blood cells after death, which may explain the unusual shapes of the structures discovered in the fossil. But another possibility remains, which is that these structures are not the remains of red blood cells at all.

Mary Schweitzer, professor emeritus of the Department of Biological Sciences at North Carolina State University, who was not involved in the study, said that the results do not meet the approved scientific standards for identifying fossilized blood cells. Schweitzer wondered whether the shape and size of the structures were sufficiently consistent with the red blood cells of organisms close to dinosaurs. She also questioned the significance of the presence of hausmanite, a type of manganese oxide that researchers found mainly in the sample, noting that this substance is not found in the red blood cells of living organisms.

But Grace explained that her team does not consider hausmanite to be an original component of the cells, but rather that it was formed during the fossilization process, and may have helped preserve the structures and associated molecular evidence. Despite her reservations about the results, Schweitzer praised the researchers' use of multiple analytical techniques, considering this an important advance in this field.

She added that she hopes that some molecules belonging to the dinosaur itself are still preserved inside the bone. She said: “Scientists have only recently begun to explore the possibility of making use of molecules preserved in fossils over long geological eras, as this type of preservation was traditionally believed to be impossible.

“The more we study very old fossils, the more we learn about the interaction between the burial environment and the organism as it decomposes.” In the future, this research may help answer broader questions about what ancient molecules reveal about diseases and biological processes, and how these molecules evolved over time.