Rare look at the last days of the dinosaurs shows they were thriving, scientists say

An artist's impression of the last dinosaurs from southern North America features a long-necked Alamosaurus. Natalia Jagielska

A site in the San Juan Basin of northwestern New Mexico is providing a rare glimpse into the last days of the dinosaurs.

Rocks and fossils at the Naashoibito Member site show an ecosystem that was filled with a diverse population of dinosaurs just before they disappeared from Earth.

Paleontologists have long debated if the dinosaurs suddenly went extinct when a 6.2-mile-wide (10-kilometer-wide) asteroid crashed into Mexico’s Yucatán Peninsula 66 million years ago at the end of the Cretaceous Period, or if they were in a gradual decline and living in weakened ecosystems ahead of the catastrophic event.

Answering that question requires finding fossils and dat