In the ancient landscape that is now New Mexico, a small beaver-like mammal managed to do what the dinosaurs could not, namely survive the apocalyptic events that wiped out not only the dinosaurs but masses of other species as well.
While an asteroid impact, earthquakes and volcanoes wiped out much of life on earth, one survivor apparently emerged, a furry, buck-toothed creature science has dubbed Kimbetopsalis simmonsae.
Identified from fossils, the new species was a member of a group of mammals known as multituberculates, named for the many cusps, or tubercles, found on their teeth.
The rodent-like animals lived alongside the dinosaurs, but unlike the doomed reptilian giants, they managed to live for another 30 million years after the asteroid that pushed the dinosaurs off the evolutionary stage.
What was bad for the dinosaurs proved a boon to Kimbetopsalis, researchers explain.
After the asteroid impact pushed many species to extinction, "all this ecological space became available and the mammals went a bit nuts," says University of Edinburgh paleontologist Sarah Shelley, co-author of a published study on the discovery.
That was particularly true of Kimbetopsalis, which evolved from a tiny creature to the size of a very large beaver in just 500,000 years, an evolutionary blink of an eye.
"This was a pretty big [multituberculate] and one that clearly ate plants, [which we can tell] because of the complexity of its teeth," says study co-researcher Steve Brusatte, also at the University of Edinburgh.
The fossil that led to the identification of Kimbetopsalis was initially discovered in 2014 in northwestern New Mexico by University of Nebraska-Lincoln undergraduate Carissa Raymond.
"I knew it was cool — but not this cool," Raymond says of her discovery.
Although New Mexico today is mostly dry, arid desert, at the time Kimbetopsalis lived, the region would have been semitropical forest, a lush environment perfect for herbivore mammals.
The fossil has been dated to between 66 million and 65.5 million years ago, just after the asteroid impact and the exit of the dinosaurs.
During most of the era of the dinosaurs, mammals were very small, no bigger than rats, which makes the discovery of Kimbetopsalis significant, the researchers say.
"It lived only a couple hundred thousand years after the extinction, so it's kind of neat to find a fairly large [mammal] — we're talking beaver size," Brusatte says.
Although it resembled modern-day rodents, Kimbetopsalis has no living descendants, the researchers note.