A bottlenose dolphin captured last month off western Japan has an extra set of fins, providing further evidence that ocean-dwelling mammals once had four legs and lived on land, Japanese researchers said yesterday.
Fishermen netted the four-finned dolphin off the coast of Wakayama prefecture on Oct. 28, and alerted the nearby Taiji Whaling Museum, according to museum director Katsuki Hayashi.
The second set of fins -- much smaller than the dolphin's front fins -- are about the size of adult human hands and protrude from near the tail on the dolphin's underside. The dolphin is 2.72m long and is about five years old, according to the museum.
"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 yesterday.
Fossil remains indicate that dolphins and whales were four-footed land animals about 50 million years ago and share a common ancestors with the hippopotamus and deer. Scientists believe they later transitioned to an aquatic lifestyle and lost their hind limbs.
The dolphin will be kept at the Taiji museum to undergo X-ray and DNA tests, Hayashi said.