Animal of the Week November 6, 2006 -- Roll up, roll up, see the freakshow dolphin

In honour of the forefinned and hindfinned, four-finned specimen caught off the coast of Japan this week, animal of the week is somewhat predictably Tursiops truncatus (bottlenose dolphin).

Bottlenoses are some of the largest dolphins and have a worldwide distribution in tropical and temperate waters. They are the typical dolphinarium dolphin, splashing spectators and firing their keepers out of the water for our entertainment in many a water park. But, as you may well have seen for yourself, they generally have only the paired pectoral fins and a dorsal fin.

So, why the bejesus does this Japanese one have four paired fins? Is it part of this highly intelligent species' plan for world domination? Will they be freeing up their forelimbs for the use of weapons of the modern age such as guns, knitting needles, or paparazzo cameras? Can we expect to see a beaky crusader creeping up the street with its sights on our pints any time soon?

Unlikely.* Fortunately for the future of the human race, this aberration is probably caused by the accidental switching on of an ancient gene that did once lead to the development of hind limbs. Believe it or not, dolphins, whales, and porpoises belong to the same group of animals as cows, giraffes, and camels -- the artiodactyls or even-toed ungulates. The closest living relatives of whales and dolphins are hippos; and rather surprisingly, cows, sheep, deer, and giraffes are more closely related to whales and hippos than they are to camels. Some innovative hippo-ish creature took the extra four-legged steps into the ocean about 50 million years ago. The whales and dolphins never looked back, becoming supreme marine mammals and streamlining by losing their hind limbs.

Atavistic features, such as this dolphin's hindfins, are not common, but nor are they unheard of: dolphins and whales with pelvic fins have been found before; and Alexander the Great's horse, Bucephalus, was said to have had additional toes with hooves resembling those of the ancestral horse merychippus. Do human's show atavistic traits, I hear you ask? Well, anyone unfortunate enough to have seen my back in my recent and advancing years will have witnessed, firsthand, evidence of our furry origins.

I thank you,

Peter Hayward
Head Keeper
Animal of the Week

*Just in case any of you sly bastards are reading this, you can keep your fins off my beer, alright.