BEIJING, Aug. 20 (UPI) -- A nearly complete fossil of the oldest ancestor of the "most evolutionarily successful and long-lived mammal lineage" has been found in China, scientists say.
Dubbed Rugosodon eurasiaticus, the newly discovered species announced by U.S. and Chinese researchers, looked a bit like a small rat or a chipmunk, China's state-run Xinhua News Agency reported.
Living 160 million years ago, it was an early member of the group of mammals known as multituberculates, which flourished across the Earth from about 170 million to 35 million years ago, the researchers said.
Multituberculates occupied a diverse range of habitats for more than 100 million years before they were out-competed by more modern rodents, they said.
"The new mammal is called Rugosodon after the rugose (corrugated) teeth ornamented by numerous tiny ridges and grooves and pits, indicating that it was an omnivore that fed on leaves and seeds of ferns and gymnosperm plants, plus worms and insects," a team of scientists from the Chinese Academy of Geological Sciences, Beijing Museum of Natural History and the University of Chicago said in a statement.
Complex teeth that allowed them to enjoy a varied diet and unique locomotive skills that enabled them to traverse treetops helped them thrive in the shadows of dinosaurs and survive through their mass extinction 65 million years ago, the scientists said, paving the way for later plant-eating and tree-dwelling mammals.