The fossil, found in Liaoning Province in northeastern China, is the earliest known skeletal fossil of a multituberculate, and offers new insight into this mammal group’s incredible success. Multituberculates thrived alongside dinosaurs for more than 100 million years and then outlived them for 30 million years before becoming extinct, making way for rodents. The newly described species, Rugosodon eurasiaticus, had highly ornamented teeth, with many wrinkles and creases. This is a sign that multituberculates started out as omnivores, researchers said. “It has lots of small ridges and grooves that are densely packed,” said Zhe-Xi Luo a paleontologist at the University of Chicago and one of the study’s authors. “In modern rodents this is related to a diet supplemented by small insects and small vertebrates.” Over time, many multituberculates evolved to become herbivores, an adaptation that helped them thrive. The researchers also discovered that the rodentlike animal had mobile and flexible anklebones, suggesting that it was a fast runner that primarily lived on the ground. “We paleontologists have always been puzzled by how some of the later multituberculates could jump from the ground and climb up in trees,” Dr. Luo said. “Lo and behold, in this early skeleton we have all those features already.” The well-equipped ankle also helped multituberculates thrive, he said. Rugosodon is described in the current issue of the journal Science.
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