Dinosaur eggshells become timing clues for ancient fossils
Scientists dated dinosaur eggshells using uranium–lead radiometric dating to determine when the eggs formed and thus when the surrounding rocks were deposited, finding about 95 million years old for Utah eggshells and about 99 million years for Mongolian eggshells, with bedrock ages matching the shell ages; the shells’ microstructure records diagenetic changes, making them a promising geochronometer for Mesozoic sedimentary basins.