Villagers digging in China's rich fossil beds have uncovered the preserved remains of a tiny dinosaur in the belly of a mammal, a startling discovery for scientists who have long believed early mammals couldn't possibly attack and eat a dinosaur. Scientists say the animal's last meal probably is the first proof that mammals hunted small dinosaurs some 130 million years ago. It contradicts conventional evolutionary theory that early mammals were timid, chipmunk-sized creatures that scurried in the looming shadow of the giant reptiles. In this case, the mammal was about the size of a large opossum, and the victim was...