Scientists Find Where Piranhas Got Their Teeth from

The name piranha alone is oftentimes enough to instill fear in the hearts of people, as it evokes those razor-sharp teeth that can tear flesh several times the size of the fish itself from virtually anything that, well, has flesh on it. But researchers studying the animals are not so puzzled by this mystery, as they are about to unveil their origins. That is to say, their closest cousin is the pacu fish, which eats only plants. Now, a new fossil seems to shed some light on the origins of piranhas, and their connections to pacus.

Back in the 1950s, researchers proposed that the piranhas and the pacus were related through a common ancestor, but that has never before been proven until now. The demonstration was made difficult by the fact that pacus have their teeth organized in double rows, whereas piranhas have a single row, like humans do. The experts back in the day said that the common ancestor of the two species would have teeth that were organized in double rows, but that showed signs that they were moving towards a single row. Such a fossil has recently been found, adding more substance to the theory.

The funny thing about the relic is that it has been found in an Argentinian museum desk drawer, collecting vast amounts of dust, while researchers were out in the South American jungle, exposing themselves to all sorts of perils just to find it. The five-centimeter fossil is of an upper-right jawbone, and it clearly shows a zig-zag tooth formation, just as one would expect from jaws reorganizing themselves from two rows of teeth to one. The new species has been named Megapiranha paranensis, and details of it have been published in the June issue of the Journal of Vertebrate Paleontology.

The Megapiranha was just as big as the modern pacus, reaching up to a meter (some three feet) in length, but a record size for a piranha. The largest piranha ever captured in modern days reaches only about 43 centimeters in length, while its standard size is 15 to 25 centimeters. The experts managed to assess the ancient fish's size by looking at its jawbone, and also by measuring countless pacus and piranha skeletons, for comparison. “It was really neat. The more we looked at it, the more things came out of it,” National Evolutionary Synthesis Center scientist and Ichthyologist Wasila Dahdul says, quoted by ScienceNow.