LAUSR

Significance We collected over 1,000 dinosaur eggshell samples from an ∼150-m-thick stratigraphically continuous fossil-rich sequence in the Shanyang Basin of central China, which is one of the most abundant dinosaur records from a Late Cretaceous sequence. We use biostratigraphy of dinosaurs and Bemalambda, magnetostratigraphy, and cyclostratigraphy from orbital cycles to establish a geochronological framework of the dinosaur fossils with a high resolution of 100,000 y. Our results demonstrate low dinosaur biodiversity during the last 2 million y of the Cretaceous, and those data indicate a decline in dinosaur biodiversity millions of years before the Cretaceous/Paleogene boundary. The end-Cretaceous catastrophic events, such as the Deccan Traps and bolide impact, probably acted on an already vulnerable ecosystem and led to nonavian dinosaur extinction.