Sixty-six million years ago, a chunk of space rock the size of a mountain slammed into the Earth. The planet would never be the same.
Debris from the impact went flying into the air, forming clouds so thick they blocked out the sun. Earthquakes shook the ground and sent massive tsunami waves roiling toward shorelines. At the same time — maybe unrelated to the impact, maybe exacerbated by it — a vast flow of lava was flooding across India, oozing ash and noxious gases that caused the climate to fluctuate like a yo-yo and may have helped kill off anything that survived the initial cataclysm.
It was not a good time to be alive, and most species made a swift exit from the global stage: Vegetation withered. Ocean life gasped for air and energy, then collapsed. Gone were the fearsome Tyrannosaurus, the winged Pterosaurs, the massive Triceratops with its three horns and bony neck frill. The dinosaurs’ 100 million-year reign had ended. And when the smoke cleared, a new hero had taken over.
It was buck-toothed and furry and had the goofy appearance of a character from a children’s cartoon. Instead of Earth-shaking stomps, it likely moved with a rodent’s fearful scurry.
Its name is Kimbetopsalis simmonsae, scientists say in a paper published Monday in the Zoological Journal of the Linnean Society. And although it was only about three feet long and no more intimidating than a beaver, it was one of the largest animals around. If Tyrannosaurus was the king of the Cretaceous, Kimbetopsalis was early royalty during the millennia that followed — an era we now call the “Age of the Mammals.”
Kimbetopsalis, which was recently discovered among the shifting sands and spooky rock formations of New Mexico’s badlands, was something of an evolutionary dark horse. First born in the Jurassic period, the fuzzy creature (creatures really — Kimbetopsalis represents a whole new genus) bided its time for a million centuries while dinosaurs tromped about.
After the meteorite-induced apocalypse, “all this ecological space became available and the mammals went a bit nuts,” explained Sarah Shelley, a paleontologist at the University of Edinburgh and a co-author on the paper.
Almost no one went more nuts than Kimbetopsalis, which grew from tiny proportions to the size of a very large beaver over the course of just 500,000 years — a mere blink of an eye in evolutionary terms. Paleontologists believe it had a beaver’s broad face and chunky frame as well, though it lacked a paddle-like tail.
Though it looks like a rodent, Kimbetopsalis has no living descendants. But it is one of the longest-living groups of mammal in history: its 160-million-year run is longer than that of any mammal species alive today.
The
teeth of Kimbetopsalis are pictured in this undated handout photo
provided by Tom Williamson. (Tom Williamson/Handout via Reuters)Raymond had never even taken a mammal biology class and had no formal training in fossil finding at the time. But when she called over project leader Thomas Williamson, curator at the New Mexico Museum of Natural History and Science, he “grinned right away,” Shelley recalled.
A new genus had just been discovered.
“It’s rare for anybody to find one of these,” Williamson said in a University of Nebraska press release. “I wish I had found it.”
Teeth are some of the most telling fossils you can find when identifying a new species, Shelley explained — they’re the best indicators of what an animal ate, and what you eat pretty much determines everything about you. From those fragments, Shelley and her colleagues gained a rough understanding of how the ancient mammal looked and lived.
Though it’s now a dry and dramatic desert, at the time New Mexico would have been a lush semitropical forest, full of sustenance for an enterprising young herbivore. Kimbetopsalis had huge, knife-like incisors were ideal for gnawing on plants. And though predators certainly existed, very distant predecessors of modern cattle and horses, life would have been a lot safer than it was before the end-Cretaceous extinction.
Kimbetopsalis was among the biggest, but it was hardly the only mammal to flourish in the newly dinosaur-free world. After epochs of living in the shadows of their larger, lizard-like contemporaries, the early years of what’s now called the Palaeogene period saw the rise of hoofed animals and opossum-like marsupials, bats and even early primates. It pays, it would seem, to be small, good at hiding and willing to wait for a meteorite to wipe out your competitors.
The rapid growth and proliferation of the Kimbetopsalis is a testament to the power of environmental change and the persistence of early mammals, researchers say.
“The history of life hinges on moments that can reset the course of evolution,” ertebrate paleontology at the University of Edinburgh and another co-author on the paper, wrote in an essay for the Conversation. Amid the destruction and rapid change caused by the meteorite impact, “dinosaurs couldn’t cope and all of a sudden they were gone. Their size and strength couldn’t save them. Mammals fared better, and now one species of brainy ape occupies that dominant place in nature that was once held by the dinosaurs.”
