New Mexico Fossils Challenge Pre-Impact Dinosaur Decline Theory Within Final 380,000 Years
Updated
Updated · spacedaily.com · Jul 5
New Mexico Fossils Challenge Pre-Impact Dinosaur Decline Theory Within Final 380,000 Years
2 articles · Updated · spacedaily.com · Jul 5
Summary
A 2025 Science study says dinosaurs in northwestern New Mexico were still thriving within roughly 380,000 years of the asteroid impact, challenging the long-held view that they were already in decline.
Andrew Flynn's team dated the Naashoibito Member using magnetic reversals and radiometric analysis, giving rare, reliable ages for fossils found so close to the end of the Cretaceous.
The site preserved a diverse ecosystem including Tyrannosaurus, Torosaurus, duck-billed dinosaurs and Alamosaurus — a 30-metre, 30-tonne sauropod that suggests giant long-necked dinosaurs had not vanished.
The authors argue the apparent decline seen in places like Hell Creek may reflect gaps in where late fossils have been found, not a continent-wide biological collapse.
Critics say one basin cannot settle the debate, noting the paper still shows western North American dinosaur species falling from about 43 to 30 over the last several million years before extinction.
Were thriving dinosaurs wiped out by history's worst case of bad luck?
Did a warm southern paradise hide the truth about the dinosaurs' decline?
Dinosaurs Thrived Until the Asteroid: New Mexico Fossils Reveal Sudden, Not Gradual, End 66 Million Years Ago
Overview
Recent research using advanced dating techniques on fossils from the Naashoibito Member in New Mexico has transformed our understanding of dinosaur extinction. Scientists found that nonavian dinosaurs were thriving in diverse and regionally unique communities right up until the asteroid impact 66 million years ago. This evidence challenges the old idea that dinosaurs were already in slow decline before the catastrophe. Instead, the findings show that the extinction was a sudden event that abruptly ended a flourishing world, highlighting the importance of precise regional studies in revealing the true story of the dinosaurs’ final days.