Dinosaur Death Impact May Have Killed More Mammals Than Thought

It is thought that about 66 million years ago, a massive impact led to the full extinction of the dinosaurs (potentially with the help of volcanoes and disease), and a significant portion of prehistoric sea life. Now researchers have found evidence that even the great majority of mammals at this time did not escape destruction.

A study recently published in the journal ZooKeys details how Metatherian mammals - the long-dead relatives of modern pouched marsupials - may have suffered near-extinction right alongside the dinosaurs at the end of the Cretaceous period, resulting in mass die-offs of countless species.

Extensively reviewed fossil records have revealed that prior to the Great Impact that wiped out the dinosaurs, the globe's metatherian mammal population was stunningly diverse. However, according to this latest study, when a 10-km wide asteroid struck what is now Mexico at the end of the Cretaceous period, a whopping two-thirds of these mammals perished - resulting in the extinction of more than 90 percent of mammalian species that had made the prehistoric Great Plains their home.

Thankfully, unlike the large and perpetually hungry dinosaurs, most prehistoric mammals were small, allowing them to survive off what sparse resources were left following the Great Impact. Some shrew-like ancestors even simply went underground and slept straight through it.

However, according to the ZooKeys study, fewer mammals than we thought had that option, especially in the case of marsupials.

"This is a new twist on a classic story," study lead Thomas Williamson, of the New Mexico Museum of Natural History and Science, said in a statement. "It wasn't only that dinosaurs died out, providing an opportunity for mammals to reign, but that many types of mammals, such as most metatherians, died out too - this allowed advanced placental mammals to rise to dominance."

"Our study shows that many mammals came perilously close to extinction," added researcher Steve Brusatte of the University of Edinburgh. "If a few lucky species didn't make it through, then mammals may have gone the way of the dinosaurs and we wouldn't be here."

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