Researchers examining a fossilised hind-leg bone from the Brazilian theropod Aratasaurus museunacionali report finding microscopic structures that resemble red blood cells, along with heme, a molecule associated with hemoglobin. The findings, published in PNAS, suggest biological traces may survive in fossils for far longer than previously thought, but do not mean that intact dinosaur blood has been found.
The team, led by paleontologists at Curtin University in Australia, studied an Aratasaurus that lived around 115 million years ago. The bone, excavated in 2008, contained blood-vessel channels filled with tiny elliptical structures. Researchers investigated whether these might have come from fungi or other microorganisms that colonised the bone after the animal died, but reported no evidence such as filaments, spores or bacterial biofilms.
Chemical testing detected heme within the structures. Heme is the oxygen-carrying component of hemoglobin, and the researchers identified it using advanced methods, including high-performance liquid chromatography coupled with mass spectrometry. They argue that the molecule likely came from the dinosaur because its composition differed from material in the surrounding rock and it was not mixed with the plant or bacterial products found in a microbial layer near the fossil.
The researchers suggest that hausmannite, a manganese oxide mineral, helped preserve traces of blood components as well as amino acids from bone collagen. The conditions where the dinosaur was buried may also have aided preservation: it lay in shallow water within a microbial mat in an environment with very little oxygen.
The team cautions that the structures should be understood as mineralised traces shaped by their geochemical surroundings, not as biological cells preserved unchanged for 115 million years. They also say the result needs to be reproduced in other fossils, geological settings and dinosaur groups before similar findings can be confirmed more broadly.
Sources: Focus.it.