Overview
- An international team’s Science paper published October 23 re-dates New Mexico’s Naashoibito Member after more than a decade of fieldwork by researchers from NMSU, Baylor, the Smithsonian and partners on BLM-managed lands.
- The fossils are dated to roughly 66.4–66.0 million years ago, placing them within about 300,000 years of the impact and contemporaneous with the Hell Creek dinosaurs in the northern Great Plains.
- Researchers combined magnetostratigraphy with detrital sanidine 40Ar/39Ar geochronology to tightly constrain the age of the fossil-bearing rocks.
- The assemblage records robust diversity, including Tyrannosaurus rex, Alamosaurus, Ojoceratops and Ojoraptorosaurus, and ecological modeling identifies temperature-driven north–south bioprovinces across western North America.
- The results bolster an abrupt, impact-driven extinction scenario for western North America while highlighting the need for additional well-dated sites to assess continent-wide or global patterns.