Asteroid that Destroyed the Dinosaurs Nearly Caused Mammals to Become Extinct

The asteroid that caused the dinosaurs to become extinct may have also almost wiped out mammals. Scientists have found that 66 million years ago, many mammals died alongside the dinosaurs.

Metatherian mammals once thrived in the shadow of dinosaurs during the Cretaceous period. The now-extinct relatives of living marsupials, metatherians had a wide range of diversity. Yet that all changed when a 10-kilometer-wide asteroid struck what is now Mexico at the end of the Cretaceous.

In the devastation that followed, a staggering two-thirds of all metatherians living in North America became extinct. This included more than 90 percent of species living in the northern Great Plains of the U.S. After this cataclysmic event, metatherians never recovered their previous diversity, which explains why marsupial mammals are rare today.

Yet some mammals took advantage of the metatherian die-off. Placental mammals, which are species that give birth to well-developed young, began their spread.

"This is a new twist on a classic story," said Thomas Williamson, one of the researches, in a news release. "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."

The findings reveal what happened after this massive impact. While previous studies believed that the die-off of the dinosaurs allowed mammals to rise to dominance, it appears that there's a more complicated story. The die-off of certain mammals allowed others to eventually take over, showing a bit more about mammalian evolution.

The findings are published in the journal ZooKeys.

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