New Evidence Debunks the Theory That Dinosaurs Were Declining Before the Asteroid

New research suggests the theory that dinosaurs were declining before Chicxulub is the result of a poor (and misleading) fossil record.

By Rosie McCall
Apr 8, 2025 8:30 PMApr 8, 2025 8:35 PM
late cretaceous floodplain
Reconstruction of a late Maastrichtian (~66 million years ago) palaeoenvironment in North America, where a floodplain is roamed by dinosaurs like Tyrannosaurus rex, Edmontosaurus annectens and Triceratops prorsus. (Image Credit: Davide Bonadonna (www.davidebonadonna.it).

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Dinosaurs were living their best life, so legend goes, until the unwelcome arrival of a killer asteroid — Chicxulub — triggered an extinction-level event 66 million years ago. That was until more recent research suggested dinosaurs were already in a state of decline and the asteroid was just the final nail in the coffin. 

Now, new findings turn this theory on its head once again, arguing that the dinosaurs’ supposed decline may, in fact, be the result of a poor fossil record.

“It’s been a subject of debate for more than 30 years. Were dinosaurs doomed and already on their way out before the asteroid hit?” lead author Chris Dean, Research Fellow in Paleontology at University College London (UCL), in the U.K., said in a press release.

According to research published in Current Biology, probably not.

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