Scientists examining a 115-million-year-old dinosaur fossil from Brazil have discovered microscopic structures resembling red blood cells, along with chemical evidence associated with ancient blood. The findings suggest that traces of delicate biological material may survive far longer than previously expected, although researchers disagree about whether the structures are definitively fossilized blood cells.
The discovery was made in the leg bones of Aratasaurus museunacionali, a meat-eating dinosaur that lived in northeastern Brazil during the Early Cretaceous period. An international research team led by Professor Kliti Grice of Curtin University in Western Australia published the findings on November 2, 2026, in the journal Proceedings of the National Academy of Sciences.
Using advanced imaging and chemical analysis, the scientists identified cell-like structures inside tiny channels that once carried blood through the dinosaur's bones. They also detected evidence of heme, an iron-containing molecule associated with hemoglobin, the protein responsible for transporting oxygen in red blood cells.
The combination of microscopic structures and chemical evidence makes the discovery especially significant. However, the researchers emphasize that they have not recovered fresh dinosaur blood, usable DNA or complete ancient blood cells.
A Dinosaur Fossil From Brazil Reveals New Evidence
The fossil belonged to a juvenile or young adult Aratasaurus museunacionali estimated to have been approximately four years old when it died. The animal measured about 10 feet long and weighed roughly 75 pounds.
Unlike the giant predators often associated with dinosaurs, Aratasaurus was a relatively small theropod. It walked on two legs and belonged to a broader group of meat-eating dinosaurs that includes the evolutionary lineage leading to modern birds.
The fossil was discovered in 2008 at a gypsum mine in Ceará state, northeastern Brazil. Its preserved remains include portions of the right femur, tibia and foot.
Researchers formally described the dinosaur species in 2020. The discovery helped improve scientific understanding of theropod diversity in South America during the Early Cretaceous.
The fossil became particularly valuable when scientists began examining its internal structure rather than focusing only on its external anatomy. Thin sections and microscopic analysis revealed details that would not have been visible through ordinary examination.
Within the bone, researchers discovered numerous rounded and elongated structures resembling ancient blood cells. Their location inside vascular canals was important because those channels supplied living bone tissue with blood.
Finding the structures in such locations strengthens the possibility that they originated from the dinosaur's biology rather than from unrelated minerals or organisms.
Chemical Tests Reveal Evidence of Heme
The researchers used several analytical techniques to examine the material, including electron microscopy and mass spectrometry. These methods allowed them to study both the physical appearance of the structures and their chemical composition.
One of the strongest findings involved heme, a molecule containing iron that forms an essential component of hemoglobin. In living vertebrates, hemoglobin allows red blood cells to transport oxygen from the lungs to body tissues.
The team detected heme-related chemical signals associated with the microscopic structures. They also identified molecular evidence that they interpreted as surviving heme components.
According to Reuters, Grice described the material as a mineral and molecular record of ancient biology rather than a sample of preserved blood. That distinction matters because fossilization can dramatically change the original composition of biological tissues.
The research also identified amino acids associated with collagen, a structural protein found in bones and connective tissue. These chemical traces offer additional evidence that some components of the original biological material may have persisted.
However, detecting collagen-related amino acids is not equivalent to recovering a complete collagen protein. Similarly, finding heme-related molecules does not mean intact hemoglobin has survived for 115 million years.
The scientists believe the strongest evidence comes from several findings considered together: the shape of the structures, their location within bone channels and the associated chemical signatures.
A Manganese Mineral May Explain the Preservation
One of the study's central questions concerns how fragile biological material could survive for such an enormous period. Ordinarily, cells and proteins begin breaking down soon after an animal dies.
The researchers identified a manganese oxide mineral called hausmannite surrounding or replacing some of the structures. They propose that this mineral helped preserve their shapes while stabilizing certain chemical remnants.
Hausmannite may have acted as a protective mineral framework during fossilization. Instead of allowing every trace of the original cells to disappear, the mineralization process could have preserved features of their structure.
The dinosaur's burial environment may also have contributed to preservation. Researchers believe the remains were rapidly buried in conditions involving limited oxygen and substantial microbial activity.
Microbial mats, which are communities of microorganisms living together in layered structures, may have influenced the chemical processes surrounding the bones. Their activity could have helped create conditions favorable to mineral preservation.
The proposed process does not mean the original blood cells remained unchanged. Fossilization involves chemical transformation, and the surviving material may be substantially different from the tissue present when the dinosaur was alive.
Understanding that transformation is essential to determining what biological information can reliably be recovered.
Scientists Disagree About Whether the Structures Are Blood Cells
Although the study presents several lines of evidence, not every paleontologist is convinced that the microscopic objects are fossilized red blood cells.
Professor Mary Schweitzer, a paleontologist at North Carolina State University known for studying dinosaur soft tissues, questioned whether the structures have the expected characteristics of blood cells.
Unlike mature human red blood cells, those of birds and other nonmammalian vertebrates contain nuclei. Schweitzer noted that the proposed fossil cells do not clearly show the nuclear features expected from such cells.
She also raised questions about their dimensions. Some of the structures appear smaller than typical red blood cells found in living nonmammalian animals.
Nevertheless, Schweitzer considered the chemical evidence for heme and collagen-related material more persuasive. Her assessment demonstrates why scientists distinguish between evidence of biological molecules and definitive identification of preserved cells.
Mauricio Barbi of the University of Regina, who was not involved in the research, similarly emphasized that identifying the structures requires interpretation. He described the combination of mineralized shapes and chemical remnants as promising while cautioning against treating them as intact blood cells.
These disagreements are an important part of evaluating the findings. The research provides evidence worth investigating without settling every question about the material's original identity.
What the Discovery Could Reveal About Dinosaurs
Most dinosaur fossils preserve hard tissues such as bones and teeth, allowing paleontologists to reconstruct anatomy, estimate growth and study evolutionary relationships.
Chemical information offers a different kind of evidence. Molecular remnants may eventually help scientists investigate how extinct animals developed, maintained their tissues and adapted to ancient environments.
Red blood cells are especially interesting because of their role in carrying oxygen. Their size, structure and chemistry are connected to the respiratory and circulatory systems of living animals.
However, the new study does not provide enough information to calculate the metabolism, oxygen requirements or behavior of Aratasaurus. Those possibilities would require further research and comparisons with other fossils.
The discovery also contributes to a broader scientific debate about the survival of ancient biomolecules. Earlier studies have reported possible blood-cell structures, collagen remnants and other organic material in dinosaur and marine reptile fossils.
Modern analytical techniques increasingly allow researchers to examine specimens at microscopic and molecular levels. Findings that were previously overlooked may become detectable as those methods improve.
Dinosaur DNA Remains Beyond the Evidence
The discovery does not bring scientists closer to cloning a dinosaur using preserved blood. Researchers found no evidence of surviving dinosaur DNA in the fossil.
DNA is chemically different from heme and many smaller molecular remnants. It generally breaks down over time, making its survival across 115 million years extraordinarily unlikely under known preservation conditions.
Grice cautioned against assuming that the presence of cell-like structures establishes the survival of complete proteins or genetic material. The study concerns mineralized structures and chemical evidence, not living cells or recoverable genomes.
The findings may nevertheless have wider implications for research into ancient life. Scientists studying fossil preservation, including those interested in astrobiology, could use similar methods to investigate whether biological chemical signatures can persist in difficult environments.
For paleontologists, one immediate opportunity lies in existing museum collections. Fossils collected decades ago may contain chemical information that earlier researchers lacked the technology to detect.
The next challenge is to determine whether the proposed blood-cell structures can be confirmed through additional testing and comparisons with other ancient specimens. That work could establish how much of an extinct animal's original biology can survive within mineralized bones for more than 100 million years.