The mass extinction event that wiped out the dinosaurs and other animals was just a blip in time for a family of beaver-resembling animals that not only survived the onslaught, but also thrived for several million years afterwards.
Paleontologists have just discovered the remains of one of these hardy, beaver-like animals. The furry, toothy mammal is called Kimbetopsalis simmonsae, a.k.a. "Primeval Beaver," and is described in the Zoological Journal of the Linnean Society.
"It is a new species of primitive beaver-like mammal from New Mexico that lived just a few hundred thousand years after the asteroid impact that killed off the dinosaurs," co-author Steve Brusatte of the University of Edinburgh's School of GeoSciences told Discovery News.
Photos: Living Fossils: Animals From Another Time
"Its ancestors made it through the firestorm and then began to evolve incredibly quickly, setting the stage for today's mammal-dominated world," he added.
Brusatte, lead author Thomas Williamson of the New Mexico Museum of Natural History and Science, and colleagues Ross Secord and Sarah Shelley analyzed the remains of Primeval Beaver, which were found in the Nacimiento Formation of the San Juan Basin of northwestern New Mexico.
Primeval Beaver was about the size of today's beavers and had large molars with several rows of cusps that it would have used to grind up even the toughest of plants. Its incisor teeth could cut through trunks, stems and more, the researchers believe.
"Plants definitely were affected by the extinction, but it's not like all plants died out," Brusatte said.
Toothy Mammal Named 'Luck' Coexisted with Dinosaurs
During the Dino Era, mammals, including the ancestors of Primeval Beaver, tended to be small. None has been found that was larger than a modern badger. This coexistence of dinosaurs and small mammals went on for over 100 million years.
Shortly after the dinos (aside from birds) were wiped off the face of the earth, mammals started to grow much larger. A close relative of Primeval Beaver was Taeniolabis, also known as "Ribbon Lips." According to Brusatte and his colleagues, Ribbon Lips weighed up to 220 pounds, and resembled an enormous beaver.
Both Primeval Beaver and Ribbon Lips were animals called multituberculates. This now-extinct group of mammals originated around 160 million years ago. It thrived for some 35 million years.
Primeval Beaver lived during the earliest Paleocene, which is one of the hottest times of the last 100 million years. During this period, there were several severe temperature spikes, called hyperthermals, which the mammals had to endure.
Primeval Beaver's environment, however, was full of rivers, swamps and lakes.
"It was an incredibly diverse habitat," Brusatte said. "Lots of turtles and alligators and birds. And also tons of other mammals. Within a few hundred thousand years after the dinosaur extinction, mammals were really prospering. Some of these were placental mammals, so early members of our group."
Eventually the multituberculates were superseded by rodents, which are placental mammals like us.
Secret to Surviving Extinction? Don't Be a Picky Eater
Brusatte explained, "Placentals generally have larger brains and grow faster than other types of mammals, like marsupials (such as kangaroos), monotremes (such as the platypus) and multituberculates."
In short, rodents had an edge on Primeval Beaver and its relatives because they were smarter, grew more quickly and reproduced faster.
Primeval Beaver and its kin, however, set the stage for the future success of beavers and other rodents.
"It's interesting that this odd, now extinct group was among the few to survive the mass extinction and thrive in the aftermath," Williamson said. "It may be because they were among the few mammals that were already well-suited to eating plants when the extinction came."
"This new species," he said, "helps to show just how fast they were evolving to take advantage of conditions in the post-extinction world."