A 115-million-year-old dinosaur bone may still hold its red blood cells

Soft tissue is not supposed to survive fossilisation — which is why what a team led by Kliti Grice of Curtin University in Australia found inside a dinosaur bone is so striking. The bone is part of a hind leg of Aratasaurus, a theropod that lived 115 million years ago, dug up in 2008 in northeastern Brazil, in rock famous for preserving remains unusually well. Inside the bone's tiny vessel channels, the researchers found masses of oval structures that look like red blood cells — and, using chemical analysis, traces of heme, the oxygen-carrying molecule in blood, detected within the structures themselves for the first time in a dinosaur fossil. The study, published Monday in the Proceedings of the National Academy of Sciences, has its sceptics, and the team is careful not to overclaim. But the methods themselves open a new door: other museum fossils may be quietly holding molecular traces of the living animals they once were.