Overview

• Using calcite from two eggshell fragments in a clutch of 28 at the Qinglongshan reserve, researchers calculated an age of about 85.9 million years with roughly ±1.7 million years uncertainty.
• The in situ carbonate U–Pb technique fires a micro-laser at eggshell carbonate to create aerosol measured by mass spectrometry to determine uranium–lead ratios.
• The Qinglongshan site in China’s Yunyang Basin preserves more than 3,000 eggs, mostly attributed to Placoolithus tumiaolingensis (Dendroolithidae) with unusually porous shells.
• Pinning the clutch to the Late Cretaceous enables tests of links between eggshell porosity and regional cooling that followed mid‑Cretaceous warmth.
• Independent paleontologists urge checks for diagenetic alteration, and the study team plans expanded sampling across rock layers and neighboring basins to verify results and build a regional chronology.