Dinosaur Eggs Help Date Climate Change Adaptations A group of 28 fossilized dinosaur eggs discovered in China's Qinglongshan fossil reserve have been dated to approximately 86 million years ago. Scientists used a precise technique known as “uranium-lead dating” to determine their age. This research may help explain how dinosaurs in the Yunyang Basin responded to changing environmental conditions during Earth's cooling period. The method used is formally called carbonate uranium-lead