TOKYO — Japanese researchers said Sunday that a bottlenose dolphin captured last month has an extra set of fins that could be the remains of back legs, a discovery that may provide further evidence that ocean-dwelling mammals once lived on land. Fishermen captured the four-finned dolphin off the coast of Wakayama prefecture (state) in western Japan on Oct. 28, and alerted the nearby Taiji Whaling Museum, according to museum director Katsuki Hayashi.