Round structures in bone channels

In a study published in Proceedings of the National Academy of Sciences, scientists examining ancient dinosaur bones report what appear to be fossilised red blood cells, with the evidence drawn from the hind leg bones of an Aratasaurus dinosaur.

• •Electron microscope images showed small, round structures resembling red blood cells sitting in fine channels where blood vessels once ran
• •Chemical tests identified the presence of heme, the organic compound that lets haemoglobin carry oxygen around the body
• •Tests also detected traces of the amino acid building blocks for collagen, a key protein in connective and other tissues

A world first, with doubts

Prof Kliti Grice of Curtin University in Western Australia, who led the research team, said fossilised red blood cells with distinct chemistry related to heme had never before been found in situ in any fossil. "We are seeing a mineral and molecular echo of the dinosaur's original biology", she said, calling the find a world first.

Such claims meet scepticism: biological tissues and molecules can break down fast, leaving little or no trace in ancient fossils. Prof Mary Schweitzer of North Carolina State University doubts the structures are red blood cells: dinosaur red blood cells should have a "nuclear bulge" making them dome-like on both sides, whereas the structures found are concave. She was more persuaded by the discovery of heme and collagen amino acids, and said the conventional wisdom that endogenous organics disappear in a million years or less is being routinely challenged.

From a Brazilian mine to the museum shelf

The Aratasaurus lived and died 115 million years ago in what is now north-eastern Brazil. The fossil was discovered in a mine in 2008 and has since been held in the National Museum of Brazil.

What may have preserved the cells

Grice suggested a manganese compound called hausmannite, formed in and around the blood cells, may have lent a helping hand by stabilising them before fossilisation, possibly also preserving the amino acids. She cautioned that the work does not imply that large biological molecules such as proteins or DNA live on in ancient fossils. "Any extraordinary claim needs extraordinary analytical evidence", she said, adding that the aim is not Jurassic Park DNA but determining how much genuine molecular information deep time can preserve.

If the find is confirmed, Grice said, it would open new avenues to investigate dinosaur blood, metabolism and even their activity levels - and extraordinary molecular information may already be sitting in museum collections around the world, awaiting new questions of old fossils.