Possible red blood cells found in bone of 115-million-year-old dinosaur from Brazil

A team led by Prof Kliti Grice of Curtin University in Western Australia says it has found structures resembling red blood cells, along with traces of heme, in the bones of Aratasaurus, a small meat-eating dinosaur that lived 115 million years ago. Heme is the organic compound that lets haemoglobin in blood carry oxygen. The study appears in Proceedings of the National Academy of Sciences. If confirmed, the finding could open new ways to study dinosaur blood, metabolism and even activity levels.

What was found

The animal lived and died in what is now north-eastern Brazil. Its remains were found in a mine in 2008 and are held at the National Museum of Brazil, where researchers are still studying them. While examining the hind leg bones, Grice noticed small, round structures in fine channels where blood vessels once ran. Electron microscope images showed that they resemble red blood cells.

Chemical tests came back positive for heme and its breakdown products. They also detected amino acids that serve as building blocks of collagen, a key protein in connective and other tissues.

According to Grice, a manganese compound called hausmannite, which formed in and around the cells, may have stabilised them before fossilisation. The same process might have helped preserve the amino acids. She says that fossilised red blood cells with heme-related chemistry have never before been found in situ in any fossil.

Doubts and caution

Such claims are controversial because biological tissues and molecules break down quickly and often leave little trace in ancient fossils. Prof Mary Schweitzer of North Carolina State University in the US, who has herself found remnants of blood vessels and soft tissue in dinosaur fossils, is not convinced these are red blood cells. She says the dinosaur's cells should have a nuclear bulge, making them dome-like on both sides, whereas the structures found are concave. She found the heme and collagen amino acid results more persuasive.

Grice urges caution and says the work does not imply that large biological molecules such as proteins or DNA survive in ancient fossils. In her words, the aim is to determine how much genuine molecular information deep time can preserve. She suggests that significant molecular information may already be sitting in museum collections, waiting for new questions.