Researchers affiliated with Stellenbosch University, alongside other institutions, have employed sophisticated uranium-lead (U-Pb) dating methodologies and detailed elemental mapping. This advanced approach allowed them to quantify minuscule quantities of uranium and lead embedded within the calcite structures of fossilized dinosaur eggshells unearthed in both the United States and Mongolia.
An artist’s reconstruction of a newly-hatched troodontid-like dinosaur among fragments of its eggshell. Image credit: Eva Utsukiyouhei.
A significant number of paleontological discovery sites globally are currently characterized by imprecise temporal estimations.
The absence of accurate chronological data pertaining to fossils presents a considerable impediment for paleontologists seeking to elucidate the evolutionary relationships and geographical distribution of various species and ancient ecosystems over vast timescales.
Conventional practices often involve the radiometric dating of minerals such as zircon or apatite that are found in proximity to fossils. However, the consistent presence of these datable minerals cannot always be assured.
Attempts to directly date the fossilized remains themselves, including bones or teeth, have frequently yielded ambiguous or unreliable outcomes.
Dr. Ryan Tucker from Stellenbosch University, along with his collaborators, embarked on an alternative investigative path. Their methodology involved the application of advanced U-Pb dating techniques and elemental mapping to meticulously measure the trace concentrations of uranium and lead contained within the calcite matrix of fossilized dinosaur eggshells.
These particular isotopes function as a natural chronometer, thereby furnishing scientists with the capability to ascertain the temporal period during which the eggs were entombed within geological strata.
Empirical findings derived from examinations of dinosaur eggs recovered from sites in Utah, United States, and the Gobi Desert in Mongolia demonstrated that the eggshells can effectively record ages with an impressive degree of precision, achieving approximately 5% accuracy when benchmarked against established dates derived from volcanic ash layers.
In the Mongolian region, the research team successfully established the inaugural direct age determination—estimated at roughly 75 million years old—for a historically significant locality that has yielded dinosaur eggs and nests.
“The calcite found within eggshells exhibits remarkable adaptability,” stated Dr. Tucker.
“It provides us with an innovative avenue for dating fossiliferous deposits where the absence of volcanic strata has historically posed a formidable challenge, one that has constrained advancements in paleontology for several decades.”
By substantiating the capacity of dinosaur eggshells to faithfully preserve a record of geological time, this research establishes a novel nexus between the disciplines of biology and Earth science, equipping researchers with a potent instrument for chronologically contextualizing fossil sites across the planet.
“The ability to directly date fossils represents a long-held aspiration within the field of paleontology,” commented Dr. Lindsay Zanno, a renowned paleontologist at North Carolina State University and the North Carolina Museum of Natural Sciences.
“Equipped with this groundbreaking methodology, we are poised to unravel profound enigmas concerning dinosaur evolution that were previously considered insurmountable obstacles.”
The collective findings of this research endeavor have been formally disseminated through publication in the esteemed scientific journal Communications Earth & Environment, accessible via the following link: work.
_____
R.T. Tucker et al. 2025. U-Pb calcite age dating of fossil eggshell as an accurate deep time geochronometer. Commun Earth Environ 6, 872; doi: 10.1038/s43247-025-02895-w
