Scientists have reported the discovery of fossilised red blood cells and heme molecules in the hind leg bones of a 115-million-year-old dinosaur from Brazil, representing a potential first in the field of palaeontology.
The remains, belonging to a small meat-eating dinosaur identified as Aratasaurus museunacionali, were discovered in a mine in 2008 and have been curated at the National Museum of Brazil. In a study published in the Proceedings of the National Academy of Sciences, an international team led by Prof Kliti Grice at Curtin University analysed the hind leg bones using electron microscopy and chemical testing.
Electron microscope images revealed small, round structures in fine channels where blood vessels once ran, which the researchers say resemble red blood cells. Chemical analysis identified the presence of heme, the organic compound that allows haemoglobin to carry oxygen around the body. The team also detected traces of hydroxyproline, an amino acid associated with collagen.
The discovery is significant because biological tissues and molecules are expected to break down quickly, leaving little or no trace in ancient fossils. If confirmed, the findings would open new avenues for scientists to investigate dinosaur blood, metabolism and activity levels.
However, the claims have drawn scepticism from the scientific community. Prof Mary Schweitzer at North Carolina State University noted that the dinosaur's red blood cells should have a "nuclear bulge" making them appear dome-like on both sides, whereas the structures found are concave, suggesting they might be something else. The study acknowledges that heme-producing microbes cannot be completely ruled out as a source of the detected compounds.
The researchers proposed that a manganese compound called hausmannite, which formed in and around the blood cells, may have helped stabilise the biological material prior to fossilisation. The same process might have helped preserve the amino acids, the team added.
The fossilised remnants of Aratasaurus offer, the researchers say, a rare glimpse into deep-time biology. "We are seeing a mineral and molecular echo of the dinosaur's original biology," said Prof Grice. "Fossilised red blood cells with distinct chemistry related to heme have never been found in situ in any fossil, let alone a dinosaur. This is a world first." The work continues to provoke debate about the limits of biological preservation and the potential for molecular information to survive across millions of years.
