But by 225 million years ago, the creatures started to look more leggy, as shown by a fossil that dates from that period, found in Madagascar . Around that time, the pelvis was becoming elongated and lined up with the spine , and the tail was receding inside the pelvis. Eventually, the tail vertebrae fused and became a structure called the urostyle, which Shubin says is crucial in transferring forces from the legs to the body during a jump. And while other animals have a pelvis that is fused to the spine, frogs developed a movable joint that allows the pelvis to slide up and down the backbone, a configuration that helps catapult frogs into the air. The Madagascar frog shows a step toward this feature, which is completely developed in the new Arizona frog, which Shubin and his colleague named Prosalirus Bitis.
Many researchers believe that jumping evolved to help frogs to escape dinosaurs and other predators.
Journey Around The Navajo Nation . The more primitive frogs have little control over their jumping, says McGill's Carroll. It's sort of random, but it usually lands them in water. Frogs survived through the age of dinosaurs and hung on through the mass extinction during which dinosaurs perished. But frogs are now disappearing all over the world , says Shubin, and no one knows why.