TOKYO Nov 6, 2006 (AP)— Japanese researchers said Sunday 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.

ossil 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.

"I believe the fins may be remains from the time when dolphins' ancient ancestors lived on land … this is an unprecedented discovery," Seiji Osumi, an adviser at Tokyo's Institute of Cetacean Research, said at a news conference televised Sunday.