Scientists find traces of red blood cells in a dinosaur fossil

Traces of prehistoric blood could reveal unprecedented clues about dinosaur biology, but they’ve been notoriously difficult to confirm. Now, researchers studying a 115 million-year-old dinosaur bone say they’ve found the strongest evidence yet of red blood cells in a fossil. Tissues, cells and other soft biological samples rarely ever survive the fossilization process and thus make for controversial discoveries. A few previous studies, dating back to the late 1990s, have reported structures resembling red blood cells in dinosaur and other reptile fossils, but researchers have fiercely debated their legitimacy. The new study, published Monday in the journal Proceedings of the National Academy of Sciences, used a combination of new microscopic imaging and chemical analyses to find not only microscopic structures resembling red blood cells preserved within the dinosaur bone, but also chemical evidence of heme — a molecule in hemoglobin, the protein in red blood cells that carries oxygen.