It has the face of a rat and the tail of a skinny squirrel — and scientists say this creature discovered living in central Laos is pretty special: It's a species believed to have been extinct for 11 million years. The long-whiskered rodent made international headlines last spring when biologists declared they'd discovered a brand new species, nicknamed the Laotian rock rat. It turns out the little guy isn't new after all, but a rare kind of survivor: a member of a family until now known only from fossils. Nor is it a rat. This species, called Diatomyidae, looks...