Researchers Discover Three Extinct Squirrel-like Species

This image is a reconstruction of arboreal mammals in a Jurassic forest. The three animals on the left side represent the three new species of euharamiyidan mammals. The other two represent a gliding species and another euharamiyidan, respectively, that were reported earlier. 
© Zhao Chuang

Paleontologists have described three new small squirrel-like species that place a poorly understood Mesozoic group of animals firmly in the mammal family tree. The study, led by scientists at the American Museum of Natural History and the Chinese Academy of Sciences, supports the idea that mammals—an extremely diverse group that includes egg-laying monotremes such as the platypus, marsupials such as the opossum, and placentals like humans and whales—originated at least 208 million years ago in the late Triassic, much earlier than some previous research suggests.