Japanese researchers have reported that a bottlenose dolphin captured last month has an extra set of fins that could be the remains of hind legs, a discovery that may provide further evidence that ocean-dwelling mammals once lived on land. Fishermen captured the four-finned dolphin alive off the coast of Wakayama in western Japan and alerted the nearby Taiji Whaling Museum. Fossil remains show dolphins and whales were four-footed land animals about 50 million years ago and share the same common ancestor as hippos and deer. Scientists believe they later transitioned to an aquatic lifestyle and their hind limbs disappeared. Though odd-shaped protrusions have been found near the tails of dolphins and whales captured in the past, researchers say this was the first time one had been found with well-developed, symmetrical fins. The dolphin measures 8.92 feet and is about five years old.