The age of the dinosaurs ended in disaster on a spring day 66 million years ago, when a 12 km wide asteroid struck Mexico’s Yucatan peninsula, driving the extinction of these gigantic creatures along with about three quarters of the species on earth.
But were dinosaurs already on the verge of extinction, with faltering diversity and poor rates of evolution, according to the perceptions of some scientists? The answer is an emphatic “no,” according to a new study that has been modeling food webs and ecological habitats in North America, the region best presented in the world’s fossil record for that era.
The researchers studied 18 million years before the asteroid impact that ended the Cretaceous period and four million years later at the beginning of the Paleogene period, when mammals asserted their dominance after the disappearance of the dinosaurs, regardless of lineages of birds that belonged to this extinct giant lineage.
Drawing on more than 1,600 fossils, the researchers reconstructed the food webs and habitat preferences of terrestrial and freshwater vertebrates. This included the likes of the giant carnivorous tyrannosaurus, the three horned dinosaur (Triceratops), ankylosaurus, crocodiles, turtles, frogs, fish and many small mammals that lived under the feet of the dinosaurs.
The researchers found that the dinosaurs were holed up in a stable, supportive environment that they adapted well to.
“In other words, dinosaurs were wiped out at the height of their prosperity,” said Jorge Garcia-Girón, an ecologist at the universities of Oulu in Finland and Leon in Spain and senior author of the study published in the journal Science Advances.
García-Giron added that mammals have begun to lay the foundations for their subsequent evolution, diversifying their ecological habitats and developing more diverse and climate-adapted diets and behaviors.
The study concluded that dinosaurs continued to evolve and adapt throughout their existence, with new species emerging and old ones disappearing. Some of the major plant eaters, such as the horned and duck-billed dinosaurs, were replaced by a larger group of mesophytic herbivores.
Some previous research has indicated that dinosaur biodiversity declined long before the asteroid impact, based on the fossil record of several dinosaur families.
Steve Brusatte, paleontologist at the University of Edinburgh and co-author of the study, said: ‘There was this nagging thought that maybe the dinosaurs were going extinct anyway, in the midst of a long decline, when the asteroid knocked them out of their power. misery.
“We can now confidently state that the dinosaurs were getting stronger, with stable ecosystems, until an asteroid suddenly killed them.”
Perhaps the good adaptation of dinosaurs to their climate and environment was the reason for their extinction.
“When the asteroid hit, it threw everything into chaos and the dinosaurs weren’t able to handle the sudden change to a world they were so used to,” Brusatte said.
And after the mass extinction, new mammals appeared.
“Mammals and dinosaurs have the same origin story. Both originated and started diversifying in the Triassic period, about 230 million years ago, on the supercontinent Pangea,” Brusatte said.
He added: ‘And from there, they each split apart, as dinosaurs made their way to the largest sizes and mammals to the smallest sizes in the shadows… But their fates will remain interconnected forever. The mammals were were present when the asteroid hit. They survived. We had ancestors who survived the asteroid.”