The coelacanth (pronounced SEE-la-kanth) is a type of primitive, slow-moving fish that was thought extinct until its rediscovery in 1938. The modern fish is sometimes called a living fossil, because it apparently existed largely unchanged for 320 million years. (See "Pictures: New 'Rebel' Coelacanth Found.")

But the newfound animal, dubbed Rebellatrix, is bizarre compared with previously known coelacanths, living or extinct, said study leader Andrew Wendruff, a biologist at the University of Alberta in Canada.

That's because all other known coelacanth species have broad tails designed to lunge short distances after prey, Wendruff said.

By contrast, the 3-foot-long (0.9-meter-long) Rebellatrix had a massive, muscular tail built for chasing prey at high speeds, much like the tail of a modern-day tuna.

"The stiff,