Fossils discovered by scientists in New Mexico belong to a previously identified type of small, furry mammal resembling modern-day rodents that were scrappy enough to thrive after the dinosaurs died out.
Originally discovered in 2014, researchers from the University of Edinburgh, the University of Nebraska, and the New Mexico Museum of Natural History and Science reported in the latest edition of the Zoological Journal of the Linnean Society that the creatures had strange, complex teeth, including sharp incisors and pointed molars well-suited for eating leaves and plants.
This type of mammal, known as a multituberculate, first arose roughly 100 million years prior to the extinction of the dinosaurs, and somehow managed to survive the events which killed off the once dominant creatures. These mammals ultimately spread through much of what is now North America and Asia, and studying them may shed new light on mass extinctions.
Despite appearances, this guy was not closely related to beavers
The fossil was discovered by a University of Nebraska student named Carissa Raymond during an annual expedition to northwestern New Mexico, which Dr. Stephen Brusatte from the University of Edinburgh School of GeoSciences called “one of the best places in the world” to find remains from these mammals.
The new species, which has been named Kimbetopsalis simmonsae, lived no more than a few hundred thousand years after the extinction of the dinosaurs, Dr. Brusatte told redOrbit via email. In a statement, he referred to the creature as a “primeval beaver” of sorts, and when asked to elaborate, he explained that it “would have looked and behaved quite a bit like a beaver. It was about the same size, had big incisor teeth at the front of its snout, and ate plants.”
Despite appearances, however, it was not a particularly close relative of beavers. It was a member of the multituberculate group of mammals, a group which eventually grew to be quite large (perhaps up to 100 kilograms in size) before ultimately going extinct when they were superseded by modern rodents approximately 35 million years ago.
Their story is our story
The discovery of the Kimbetopsalis simmonsae has helped scientists update the family tree of these mammals, the researchers said in a statement. This work reveals that the new fossil dates back to approximately 500,000 years after the mass extinction, and that this so-called “primeval beaver” was likely a forebear to the largest multituberculates.
“This gives us a glimpse of how these big multituberculates got started after the dinosaurs went extinct: they rapidly evolved right after the asteroid hit,” Dr. Brusatte told redOrbit, adding that it reveals much about the extinction event at the end of the Cretaceous and the subsequent recovery from what he calls “one of the worst mass extinctions in earth history.”
“An asteroid fell out of the sky one day and the world changed in an instant,” he said. “Dinosaurs had been dominant for over 100 million years and they quickly disappeared. Mammals – which had been living in the shadows of the dinosaurs for many tens of millions of years – made it through the extinction and suddenly had the opportunity to diversify in the brave new world. And they did this quickly, very quickly.”
“This new species lived only a few hundred thousand years after the dinosaur extinction. It ate plants and was the size of a beaver,” Dr. Brusatte added. “There weren’t any mammals like this that lived with the dinosaurs… so it looks like mammals rapidly began to get bigger, evolve new diets, and colonize new environments very, very soon after the dinosaurs bit the dust. That’s a neat story, because that is the story of how we got here. That explosive diversification of mammals led to primates, which led to us.”
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Feature Image: Sarah Shelley, University of Edinburgh
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