An international team of researchers has discovered mineralized structures resembling red blood cells and chemical traces of heme — the key component of hemoglobin — in the bones of the dinosaur Aratasaurus museunacionali.
The remains belong to a small predatory theropod that lived in what is now northeastern Brazil about 115 million years ago, in the Early Cretaceous period. The hind-limb bones were found back in 2008 in a gypsum quarry.
Under the microscope, the scientists saw ellipsoidal formations measuring on average 23 by 20 micrometers inside the channels where blood vessels once ran. These structures were mineralized by manganese oxide, specifically the mineral hausmannite.
Chemical analysis confirmed the presence of the molecule heme B and its modified form 3,8-diethyl heme B. These compounds are directly linked to hemoglobin, which carries oxygen in the blood. Traces of collagen amino acids also point to the preservation of organic components.
The study was published in the Proceedings of the National Academy of Sciences. The work was led by Professor Kliti Grice of Curtin University in Australia. "To find intact heme derivatives in red blood cells 115 million years old is astonishing," she noted.
The authors emphasize that this does not mean whole blood or hemoglobin proteins have been preserved in the fossils. What is at issue are mineralized remains and molecular signals that provide an "echo" of ancient biology.
Previously, such finds raised doubts because of possible contamination or resemblance to minerals. Here the team conducted about 30 tests, including laser spectroscopy and X-ray analysis, and ruled out alternative explanations.
How could this have been preserved? The researchers suggest that the dinosaur was quickly buried under conditions of low oxygen content and a microbe-rich environment, and that mineralization acted as a natural time capsule.
The discovery calls into question previous ideas about how long biomolecules can persist in geological time. What new windows into the physiology of extinct animals will it open?
The work was carried out by an international team with the participation of scientists from Australia, Japan, Brazil and the United States. It may influence approaches to the search for ancient life not only on Earth but also beyond it.
