Dolphin with "Remains of Legs"

Researchers in Japan captured a bottlenose dolphin that has an extra set of fins that could be the remains of back legs (see picture). This discovery may provide further evidence that dolphins once lived on land.

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.