Dolphin with Vestigial Fins

from the Daily Mail

As they leap over the waves and perform their extraordinary acrobatic feats, dolphins are the embodiment of water-borne grace. Yet, almost incredibly, this was not always their element. Experts believe that the dolphin's ancestor was a dog-like creature which roamed the earth many millions of years ago. And now the extraordinary discovery of a bottlenosed dolphin with an extra set of flippers has provided living proof of the theory. At first glance it looks like any other of its kind. But closer inspection reveals a rogue set of rear fins.

Each the size of a human hand, the fins are thought to be the remains of a pair of hind legs, adding to evidence that dolphins once walked on all fours. While dolphins with odd-shaped lumps jutting out near the tail have been caught before, this five-year-old bottlenose is thought to the first with a full second set of fins.

Scientists have so far been unable to tell whether the four-finned dolphin, caught in fishermen's nets off Japan's Wakayama province a week ago, uses its extra set of fins when swimming. The creature, 9ft from nose to tail, is now in a tank at a whaling museum where it will undergo both X-ray and DNA testing.

Recent fossil finds support the belief that, 50-million years ago, forerunners of the present deep-sea mammals had limbs and were quick on their feet. It is thought the dolphin's land-loving ancestors first crawled into the sea to escape predators or seek food between 50-million and 35-million years ago. Their hind legs became smaller and smaller before eventually disappearing altogether. The new aerodynamic shape reduced drag in the water, speeding their swimming. Further evidence of the dolphin's past as a land-dweller comes from its inability to breathe u under water, and the bones of its fins, which are very similarly jointed those in the human hand.