A research team led by Professor Kliti Grice at Curtin University in Western Australia says it has found small, round structures resembling red blood cells inside microscopic channels where blood vessels once ran, while analyzing the hind-leg bone of the dinosaur Aratasaurus — a small predator that lived and died in what is now northeastern Brazil 115 million years ago.
Images under an electron microscope revealed the structures, while chemical tests confirmed the presence of heme, the organic compound that allows hemoglobin in blood to carry oxygen around the body. The tests also found traces of the amino acids that make up collagen, a key protein in connective and other tissues.
“We are seeing the mineral and molecular traces of primitive biology in dinosaurs,” Grice said. “Fossilized red blood cells with their own distinct chemistry linked to heme have never been found in place in any fossil, let alone a dinosaur. This is a world first.”
The Aratasaurus fossil was discovered at a mine in 2008 and is now held at Brazil’s National Museum, where researchers continue to analyze it. While studying the hind-leg bone, Grice noticed the red-blood-cell-like structures. Her suspicion was strengthened when chemical tests came back positive for heme and its breakdown products.
According to Grice, a manganese compound called hausmannite that formed in and around the blood cells may have helped stabilize them before fossilization, while also preserving the amino acids. The study was published in the Proceedings of the National Academy of Sciences.
The finding, however, is disputed. Professor Mary Schweitzer at North Carolina State University in the United States, who has previously found traces of blood vessels and soft tissue in dinosaur fossils, does not believe Grice’s team found red blood cells. One reason is that dinosaur red blood cells should have a “nuclear bulge” that makes them look domed on both sides, whereas the structures Grice found are concave, suggesting they may be something else.
Schweitzer was more convinced by the discovery of heme and collagen amino acids in the bone, and said there is still much to learn from exceptionally well-preserved fossils. “The traditional view in paleontology that all endogenous organic material disappears within a million years or less is being challenged regularly, and will continue to be as technological methods are applied more widely to paleontological samples,” she said.
The research also raises questions about what other biological materials may be hiding in fossil collections around the world. On that point, Grice urged extreme caution, stressing that her work does not imply that large biomolecules such as proteins or DNA survive in ancient fossils. “Any extraordinary claim requires extraordinary analytical evidence,” she said. “The goal is not to find Jurassic Park DNA, but to determine how much authentic molecular information deep time can preserve.”
According to Grice, the truly exciting implication is that extraordinary molecular information may already be sitting in museum collections around the world, waiting for us to ask new questions of old fossils.
