Ancient beaver-like mammal survives dinosaur apocalypse, thrives

Recently, scientific news has been filled with renewed interest in the fate of the dinosaurs. The mass extinction that occurred approximately 66 million years ago has captured the imagination of generations. However, little attention is given to those that survived the prehistoric apocalypse.

Kimbetopsalis simmonsae, as known as the ‘Primeval Beaver’ was a small, furry creature related to the modern day beaver. Its Latin name literally means “Simmon’s cutting shears of Kimbeto Wash”. The name is a series of honors. The first part of the name is the place where the fossils were found (Kimbeto Wash); the second, psalis, comes from the Greek word meaning ‘cutting shears’ in reference to the creatures front teeth; and the last portion was given in recognition of the renowned mammal paleontologist Nancy Simmons for her work on similar species.

“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,” said co-author Steve Brusatte of the University of Edinburgh’s School of GeoSciences.

The Primeval Beaver would have been about three feet long and weighed about 22 pounds. This hardy critter not only managed to survive, it thrived.

This revelation of mammal superiority comes has a team of scientist from the University of Edinburgh and the New Mexico Museum of Natural History and Science unearthed fossilized remains of the Primeval Beaver in the Nacimiento Formation of the San Juan Basin in northwestern New Mexico.

“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,” said Brusatte.

“Its ancestors made it through the firestorm and then began to evolve incredibly quickly, setting the stage for today’s mammal-dominated world.”

The Primeval Beaver would have been roughly the same size as the modern beaver. It also had the beaver’s trademark large teeth. Additionally, the Primeval Beaver had several rows of cusps- perfect for grinding up tough plants.

Scientists believe that one of the reasons this creature was able to survive was that it could consume relatively unappetizing food that remained after the calamities. This would include bark, tree trunks, plant stems, and more.

“Plants definitely were affected by the extinction, but it’s not like all plants died out,” said Brusatte.

The days that the Primeval Beaver roamed the Earth were some of the hottest times in the last 100 million years. Known as the early Paleocene, this time period was marked by severe temperature spikes called hyperthermals.

Fortunately, the environment in which the Primeval Beaver lived was full of water to cool off in; there were plenty of rivers, lakes, and swamps.

“It was an incredibly diverse habitat,” said Brusatte. “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.”

Mammals existed alongside dinosaurs for at least 100 million years. In general, these ancient mammals tended to be small, no bigger than the modern badger. It was only after the dinosaurs were wiped out that the mammals began to grow larger.

One mammal that certainly seemed to thrive post-dinosaurs was the Primeval Beaver’s cousin Taeniolabis also known as ‘Ribbon Lips’. Ribbon Lips also resembled a beaver but was enormous. The New Mexico team estimates that they weighed around 220 pounds.

“They weren’t elephants, but for this early on, they were pretty big,” said Brusatte.

Both Primeval Beaver and Ribbon Lips are members of an animal family known as multituberculates. They are thought to have originated some 160 million years ago. These creatures are now extinct.

In time, rodents overtook the multituberculates. Rodents are placental animals like humans. They might have been able to outsmart the Primeval Beaver and others in competition for food and territory. They also grew and reproduced faster than the multituberculates, which would have offered another competitive edge.

“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,” said Brusatte.

“Whether the rodent outcompeted them or whether it was more a break for rodents that the multituberculates were already declining, it’s hard to say,” said Brusatte. “But the general gist of it is that the multituberculates went extinct about 35 million years ago or so, and they were superseded by rodents.”

“It’s interesting that this odd, now extinct group was among the few to survive the mass extinction and thrive in the aftermath,” said lead author Thomas Williamson of the New Mexico Museum of Natural History and Science. “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 helps to show just how fast they were evolving to take advantage of conditions in the post-extinction world.”

Much more evidence is needed to fully understand the ways of the Primeval Beaver and those who may have roamed the earth with him. The New Mexico discovery offers just a peak at the extraordinary history that ultimately led to life on earth as we now it today.

“It’s part of that picture that shows how quickly mammals started to blossom, and how quickly they started to evolve and create a whole new world really within thousands and thousands of years of the extinction,” said Brusatte.



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