Hell Creek Formation Precisely Dated to 66.895 Million Years – Pinpointing the Exact Moment the Dueling Dinosaurs Lived

A groundbreaking 2026 PLOS ONE study has delivered the most precise age ever ᴀssigned to any dinosaur locality in the Hell Creek Formation: 66.897 +0.023/−0.028 million years ago for the Dueling Dinosaurs site in Montana. Using high-precision CA-ID-TIMS U-Pb zircon dating of bentonite layers immediately above and below the fossils, researchers led by Eric Roberts have anchored the famous Triceratops–Nanotyrannus pair to within ~50,000 years of the K-Pg boundary.

This level of chronological control is unprecedented for terrestrial dinosaur sites. Previous estimates placed the formation broadly between 68–66 Ma; the new dates reveal that the Dueling Dinosaurs lived just 50,000–100,000 years before the Chicxulub impact. The Bayesian age-stratigraphic model also revises the base of the Hell Creek Formation upward, shortening its total duration and тιԍнтening correlations across the Western Interior.

The implications are profound. With such тιԍнт temporal brackets, paleontologists can now link the Dueling Dinosaurs directly to the final pulses of Deccan volcanism and the environmental stress that preceded the asteroid strike. The precise age confirms that Nanotyrannus lancensis (“Bloody Mary”) and its Triceratops adversary coexisted during the very latest Maastrichtian—ruling out any possibility they represent earlier, pre-extinction faunas.

“This is the gold standard,” Roberts stated. “We now know exactly when these two dinosaurs fought and died, right at the edge of the Cretaceous.” The study also dates the Ingomar bentonite and other key marker beds, providing a new regional framework for the entire Hell Creek ecosystem.

After two decades of uncertainty, the Dueling Dinosaurs finally have a birth certificate accurate to the nearest 50,000 years—placing their final battle squarely in the last chapter of the Age of Dinosaurs.