Despite previous research, Earth's long-gone mega-reptiles probably weren't dying off before an impact winter did them in for good.

A new study challenges the long-held belief that dinosaurs were already declining before the asteroid impact 66 million years ago. University College London researchers suggest that the apparent decline of these dinosaurs before the impact might be an illusion created by a patchy fossil record.

Fossils from the late Cretaceous are less likely to be discovered, say researchers, primarily because of fewer locations with exposed and accessible rock.