Scientists from Stellenbosch University and elsewhere used advanced uranium-lead (U-Pb) dating and elemental mapping techniques to measure trace amounts of uranium and lead in the calcite of fossilized dinosaur eggshells found in the United States and Mongolia.
An artist's reconstruction of a newly hatched troodontid dinosaur among fragments of its eggshell. Image credit: Eva Utsukiyohei.
Many fossils around the world are only approximately dated.
Without accurate information about the geological age of fossils, paleontologists have difficulty understanding how different species and ecosystems are related in time and space.
They usually rely on dating minerals such as zircon or apatite found in fossils, but these minerals are not always present.
Attempts to date the fossils themselves, such as bones or teeth, have often yielded uncertain results.
Dr Ryan Tucker and his colleagues at the University of Stellenbosch took a different approach: they used advanced U-Pb dating and elemental mapping techniques to measure trace amounts of uranium and lead contained in the calcite of fossilized dinosaur egg shells.
These isotopes act as a natural clock, allowing scientists to determine when the eggs were buried.
Tests of dinosaur eggs from Utah in the United States and the Gobi Desert in Mongolia showed that eggshells recorded ages with an accuracy of about 5% relative to the exact dates of volcanic ash.
In Mongolia, researchers have for the first time determined the direct age – about 75 million years – of a historical site where dinosaur eggs and nests were preserved.
“Eggshell calcite is amazingly versatile,” Dr. Tucker said.
“This gives us a new way to date fossil sites where volcanic layers are missing, a problem that has limited paleontology for decades.”
By showing that dinosaur eggshells can reliably record the passage of geological time, the study links biology and earth science in new ways, offering researchers a powerful tool for dating fossil sites around the world.
“Direct dating of fossils is a paleontologist's dream,” said Dr. Lindsay Zanno, a paleontologist at North Carolina State University and the North Carolina Museum of Natural Sciences.
“Armed with this new technology, we can unravel mysteries of dinosaur evolution that were previously intractable.”
teams Job was published in the magazine Connection Earth and environment.
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RT Tucker etc.. 2025. U-Pb calcite dating of fossil eggshells as an accurate deep-time geochronometer. Commune Earth Environment 6, 872; doi: 10.1038/s43247-025-02895-w
