Dinosaur extinction has been one of the world’s most dramatic mass extinctions. Though there have been many theories about their possible cause of extinction, it is still a matter of debate with no clear consensus. One of the theories says that about 66 million years ago, a massive meteorite event (referred to as the Chicxulub catastrophe) struck Earth at the Gulf of Mexico. This lead to cataclysmic climate changes, wiping off all the dinosaurs at once.
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This extinction at the Cretaceous–Paleogene (K-Pg) may be more than what meets the eye. A recent study published in the Proceedings of the National Academy of Sciences by Manabu Sakamoto (post doctoral fellow, University of Reading), Michael J. Bentonb (University of Bristol) and Chris Vendittia (University of Reading) challenges the existing theory. With their novel approach to statistically analyze speciation and extinction, the researchers resorted to Bayesian phylogenetic approach to study the dynamics of the three subclades of dinosaurs: Ornithischia (beaked herbivores), Sauropodomorpha (long-necked plant-eaters), and Theropoda (flesh-eaters).
It was found that the dinosaur population’s slow decline began about 24 million years before the Chicxulub event. This decline of the existing population was not replenished, making the species vulnerable to extinction. The Chicxulub event then became the final nail in the coffin, instead of the actual cause of extinction. It must be noted that the statistical violations which were previously ignored were also taken into account during the study.
The reason for the decline is suspected to be due to deadly tectonic shifts during the Cretaceous period (145.5 million-65.5 million years ago), although there is no concrete evidence to prove it.
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Drastic geological changes caused Earth’s two supercontinents to drift apart, temperatures to dip, sea levels to fluctuate and there was persistent volcanic activity. Simultaneously, India’s Deccan Traps saw eruption of megavolcanoes that might have driven the dinosaurs to extinction, as suggested by Gerta Keller (Professor of Geoscience, Princeton University). These events, consequently, lead to the attenuation of the dinosaurs’ habitat. According to Sakamoto and Venditti, “Any combination of these processes could have affected dinosaur speciation”. The authors believe that the dinosaurs were probably under stress for a prolonged period.
Disagreeing to this latest finding, Stephen Brusatte (Palaeontologist, University of Edinburgh) says that the decline was “very, very plausible” but that doesn’t mean dinosaurs were “wasting away” towards extinction, as reported by The Guardian. He believes, however, that they could have bounced back from the brink of extinction.
As said by Stephen, “It may be that the effects of the asteroid were a bit worse because you had dinosaurs that maybe weren’t as strong in an evolutionary sense as they once had been…But I think if there was no asteroid you would still have dinosaurs around today.”