PIRANHA PICTURES: Yard-long "Megapiranha" Fossil Found

Eight to ten million years ago, South America's waters harbored a toothier, three-foot (one-meter) version of today's famed, flesh-eating piranhas.

Alberto Cione, a paleontologist at Argentina's La Plata Museum, first noticed the evidence of Megapiranha pananensis (pictured in an artist's rendering)--an upper jaw with three unusually large and pointed teeth--in his collection in the 1980s. The remains had been discovered half a century earlier in a riverside cliff in northeastern Argentina.

Cione and his colleagues now report that Megapiranha bridges the evolutionary gap between modern-day piranhas and plant-eating pacu fish. The new study appears in the June 2009 issue of the Journal of Vertebrate Paleontology.