Study shows dinosaurs were ‘hit in their prime’ by an asteroid

WASHINGTON (Reuters) – The age of the dinosaurs ended in disaster one spring day 66 million years ago when a 12-kilometre-wide asteroid slammed into Mexico’s Yucatan peninsula, wiping out the magnificent beasts and nearly three-quarters of the planet. Ocean.

But were dinosaurs really on their way out, with diversification faltering and rates of evolution fading, as some scientists have suggested? The answer is an emphatic “no,” according to a new study that modeled food chains and ecological habitats in North America, the part of the world best represented in the fossil record from that time.

The researchers studied 18 million years before the asteroid impact that ended the Cretaceous period and 4 million years after that at the beginning of the Paleogene, when mammals asserted their dominance after the demise of the dinosaurs–regardless of the lineage of birds.

Based on more than 1,600 fossils, the researchers reconstructed the food chains and habitat preferences of terrestrial and freshwater vertebrates. This included the likes of the giant meat-eating Triceratops, the three-horned Triceratops, the tank-like Ankylosaurus, crocodiles, turtles, frogs, fish, and the many small mammals that lived under the feet of the dinosaurs.

The researchers found that the dinosaurs were entrenched in stable ecological niches to which they adapted well.

“In other words, dinosaurs were wiped out in their prime,” said ecologist Jorge García-Girón of the University of Oulu in Finland and the University of León in Spain, lead author of the research published in the journal Science Advances.

Mammals began to lay the foundation for their later rise, García-Girón added, diversifying their ecological niches and evolving more diverse diets, behaviors, and climate tolerances.

The study found that dinosaurs continued to evolve and adapt during their reign, with new species emerging and old ones disappearing. Some major plant eaters such as the horned and duck-billed dinosaurs have been replaced by a larger group of medium-sized herbivores.

Some previous research has suggested that dinosaur biodiversity declined long before the asteroid impact, based on the fossil record of different dinosaur families.

“There was this nagging thought that perhaps dinosaurs were on their way out anyway, in the midst of a protracted decline, when the asteroid put them out of their misery,” said University of Edinburgh paleontologist and study co-author Steve. Brosat. “We can now say with conviction: the dinosaurs were strong, with stable ecosystems, until suddenly an asteroid killed them.”

Perhaps the fact that dinosaurs were so well adapted to their climate and environment is the reason for their decline.

“When the asteroid hit, it threw everything into disarray and the dinosaurs couldn’t handle the sudden change of a world they were so used to,” Brusatte said.

said paleontologist and study co-author Alfeo Alessandro Chiarenza of the University of Vigo in Spain.

Pre-asteroid mammals included a now-extinct rodent-like group called the multituberculate, as well as relatives of today’s marsupials called metatherians and relatives of today’s placentals called eutherians.

After the mass extinction, new mammals emerged, including many true placentals—the group that gives birth to well-developed young, and includes most mammals today from whales to bats and porpoises to humans. Post-apocalyptic mammals rapidly expanded in body size and ecological diversity.

“Mammals and dinosaurs have the same origin story — they both originated and began diversifying in the Triassic period, about 230 million years ago, on the supercontinent Pangaea,” Brusatte said.

“From there, they went their separate ways, with dinosaurs edging toward greatness and mammals down to small sizes in shadow,” Brusatte added. “But their fates will be forever intertwined. Mammals were there when the asteroid hit. They made it through. We had ancestors who stared at the asteroid.”

(Reporting by Will Dunham in Washington; Editing by Rosalba O’Brien)

Our Standards: The Thomson Reuters Trust Principles.

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