Download dinosaur peak1/5/2024 ![]() ![]() ![]() And yet other groups of animals and plants survived through this singular, short-term crisis 26, 27. It has proved harder to posit a convincing killing model that explains exactly how the dinosaurs, as well as many other groups 24, 25, vanished. If extrinsic events had a role, the question is whether this driver was terrestrial or extra-terrestrial 21, 22, 23. Although evidence for an end-Cretaceous impact is indisputable 6, most scientific debate has focused on whether the extinction was geologically abrupt or gradual 7, 8, 9, 10, 11, whether it was caused by factors intrinsic to dinosaurs 12, 13, 14, 15 or by extrinsic physical drivers 16, 17, 18 or both acting in concert 19, 20. The best-supported extinction model is the impact of a large asteroid in the Yucatán Peninsula (Chicxulub, Mexico), which set off a global cataclysm and environmental upheaval 4, 5. The most famous mass extinction was the disappearance of non-avian dinosaurs at the end of the Cretaceous, 66 million years ago (Mya), after ruling the Earth for 170 million years 1, 2, 3. ![]() These results support an environmentally driven decline of non-avian dinosaurs well before the asteroid impact. ![]() We also estimate that extinction risk is related to species age during the decline, suggesting a lack of evolutionary novelty or adaptation to changing environments. The latter is likely due to hadrosaurs outcompeting other herbivores. We investigate the influence of ecological and physical factors, and find that the decline of dinosaurs was likely driven by global climate cooling and herbivorous diversity drop. We analyse the speciation-extinction dynamics for six key dinosaur families, and find a decline across dinosaurs, where diversification shifted to a declining-diversity pattern ~76 Ma. A sudden extinction caused by an asteroid is the most accepted hypothesis but it is debated whether dinosaurs were in decline or not before the impact. The question why non-avian dinosaurs went extinct 66 million years ago (Ma) remains unresolved because of the coarseness of the fossil record. ![]()
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