Discovery of Mammals that Survived Dinosaur Extinction

When we think of dinosaurs, we often conjure up images of these huge beasts, bigger than houses, strong and capable of withstanding anything - except for an extinction-causing asteroid smashing into the planet. Those dinosaurs didn't stand a chance, so it's hard to imagine that much else would have. But according to a paper published on Monday in the Zoological Journal of the Linnean Society, there was an ancient species of mammal that managed to survive that extinction level event. Not only that, but it would go on to thrive for a further 100 million years until rodents took their place about 35 million years. After the dinosaurs had died out, mammals appeared to take over, and the remains of a newly discovered creature could give us clues as to how this happened. The fossil of this now extinct animal was discovered by Carissa Raymond, a student of Edinburgh University's Dr Steve Brusatte. Dr Brusatte was lead researcher for the paper, but you might already have heard of him from his work on the BBC's Walking with Dinosaurs. Dr Brusatte said that it soon became apparent that the fossil belonged to a new type of mammal that no one had seen before. The animal's teeth, in particular, were specialised for chewing on plants, making it clear that this new-but-ancient mammal was a herbivore. At the back of its mouth sat complicated rows of cusps (the cutting edges of teeth) and in the front were incisors for gnawing. Raymond found the fossil on site in Kimbeto Wash, a badland area of New Mexico in the US. This location lent its name to the creature, Kimbetopsalis simmonsae. The second part of its name, "psalis", is in reference to its teeth and means "cutting shears". After intense study of the remains, the team determined that the Kimbetopsalis was a plant-eating mammal that resembled a beaver or large rodent, although it wouldn't have been closely related to either of these. The scientists were also able to gauge an approximate weight of 40kg (88lb) from the fossils and estimated the creature to be just under 0.5 metres long (1.6 feet). Further examination led to the team to confirm their belief that Kimbetopaslis belonged to a now-extinct group of animals called multituberculates, so named because of their vast number of teeth. Multituberculates actually originated alongside the dinosaurs of the Jurassic period. And with the dinosaurs no longer around, these creatures started taking over the world, increasing in both size and number. It is thought that this is why there are so many varying mammals around now. "A whole lot of mammals did die," said Dr Brusatte. "But this group is one that made it through pretty well. "Literally, the world changed one day." Dr Thomas Williamson, the corresponding author of the paper from the New Mexico Museum, described the Kimbetopsalis finding as a pleasant surprise that filled an important gap in the knowledge and record of mammals. He said that it was interesting that this group of animals was among the few to survive the dinosaur extinction and go on to thrive afterwards. Dr Williamson also hypothesised that the survival could have been something to do with the animals already being well-adapted to eating plant matter. But whatever the reason, the remains help to show just how quickly the group of animals could evolve "to take advantage of conditions in the post-extinction world". Dr Brusatte agreed and explained that in relative terms, the mammals that survived what the dinosaurs couldn't began to recover quite quickly, and it's because of this that our own ancestors got their start. "The history of life hinges on moments that can reset the course of evolution," Dr Brusatte declared. He explained that despite the size and strength of the dinosaurs, they weren't able to make it through the asteroid collision. "Mammals fared better," he said. "Now, one species of brainy ape occupies that dominant place in nature that was once held by the dinosaurs."