Dinosaurs were victims of the cold wave before the coup of mercy | science | news | the sun

TheThe extraterrestrial responsibility for its disappearance has been a consensus within the scientific community since the discovery of the giant impact crater in 1980 in Mexico. The collision caused such a shock wave that the Earth was covered in a cloud of dust and gas, upsetting the climate and permanently wiping three-quarters of species, including non-avian dinosaurs, off the map. But paleontologists are arguing over whether this mass extinction occurred suddenly, or whether the meteorite just delivered the final blow to an already struggling group.

Biologist Fabian Condamine, author of the study published in Nature Connections. Because the data is not robust enough to validate one hypothesis rather than another: “The fossil record (dinosaur bones, editor’s note) is incomplete, in poor state of preservation, certain geographic regions such as the tropics are poorly represented, and time periods are better informed than others … ”, developed by the CNRS researcher at the Institute of Evolutionary Sciences in Montpellier.

1600 fossils

To correct these biases, the researcher and his French-Anglo-Canadian team used a new method of statistical modeling, called Bayesian, which calculates the probabilities of causes from observing known elements. They selected 1,600 fossils belonging to six families of dinosaurs, including the iconic tyrannosaurs, triceratops and hadrosaurs, once famous Jurassic Park.

Three families of herbivores, and three of carnivores, are rich in 247 species. Each fossil is assigned a code which makes it possible to trace the successive diagnoses that scientists have made since their discovery. Grâce à leur modèle, les chercheurs ont pu estimer un âge d’apparition et d’extinction pour chacune des espèces, sur une période allant de 145 millions d’années, à la fin du Crétacé’u an à né 66 millions d Disaster.

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As a result, “we see a peak in diversity 76 million years ago, with a high rate of formation of new species. Then there was a slow decline,” Fabian Condamine explains. Thus, over a colossal period of 10 million years, the number of dinosaur species declined, from about fifty to less than twenty 66 million years ago. The researchers compared these statistics with already known and indisputable environmental data (climatic, marine, geological, etc.).

drop from 7 to 8 degrees

The results showed a perfect correlation with the climatic curves: “The higher the rate of species disappearance, in the mirror, the lower the temperatures,” the expert on macroevolution explained. This significant cooling, which caused the Earth to lose 7-8 degrees, begins “right” at the same time as the dinosaurs’ decline.

“Back then, it was much warmer, and there were palm trees and mangrove forests in the Bering Strait” between Siberia and Alaska today, explains Fabian Kondamine. However, these giants are unable to produce their own body heat, as humans do. They depended too heavily on their environment for food, movement, reproduction…so their metabolism was not able to adapt to the change.

Another key variable: the first disappearances affected herbivores, about two million years before the carnivores. The study suggests that the dearth of herbivores, the prey of carnivores, may have unbalanced ecosystems and lead to successive extinctions among other dinosaur families.

In this context, a meteorite with a diameter of 12 km hit the Earth. Already weakened, the rule of giants could not recover from this catastrophe, unlike some small mammals.

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