During the Cretaceous period, Earth experienced intense volcanic eruptions, widespread depletion of oxygen in the oceans, and multiple mass extinction events. Fossils from this time have been preserved and still provide scientists with valuable insights into what the climate may have been like in different parts of the world.

A group of researchers in China has now analyzed a remarkable set of these fossils: dinosaur eggs discovered at the Qinglongshan site in the Yunyang Basin in central China. For the first time, scientists successfully applied carbonate uranium-lead (U-Pb) dating to determine the age of dinosaur eggs. Their findings were recently published in Frontiers in Earth Science.

“We show that these dinosaur eggs were deposited roughly 85 million years ago, in the Late Cretaceous period,” said corresponding author Dr Bi Zhao, a researcher at the Hubei Institute of Geosciences. “We provide the first robust chronological constraints for these fossils, resolving long-standing uncertainties about their age.”