Overview
- Published October 23 in Science, the study re-dates the Naashoibito Member in New Mexico to about 66.4–66.0 million years ago, contemporaneous with the Hell Creek Formation.
- Researchers combined argon-isotope measurements of volcanic grains with paleomagnetic polarity data to constrain the site’s age within a few hundred thousand years of the asteroid strike.
- The fossils reveal a vibrant, regionally distinct southern community featuring giants like Alamosaurus and crested lambeosaurines, contrasting with northern faunas that lacked sauropods and had different duck-billed dinosaurs.
- The findings support a picture of diverse, functioning ecosystems up to the end of the Cretaceous, countering a simple narrative of a long-term continental decline before extinction.
- Independent paleontologists welcome the precise dates but note that a single well-dated locality cannot settle global diversity trends or clarify contributions from other late-Cretaceous stressors, underscoring the need for more sites.