Toothy 3-foot Piranha Fossil Found

If you thought piranhas were scary, be glad Megapiranha is no longer around.

Megapiranha was up to 3 feet long (1 meter) – a fish-beast four times as big as piranhas living today, studies of its jawbones indicate. It lived about 8 million to 10 million years ago and might have been quite comfortable stalking cartoon animals in an “Ice Age” movie.

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Now a newly uncovered jawbone of a transition species ties all these teeth together. Named Megapiranha paranensis, this previously unknown fossil fish bridges the evolutionary gap between flesh-eating piranhas and their plant-eating cousins.

Here’s what’s known:

Present-day piranhas have a single row of triangular teeth, like the blade on a saw, explained the researchers. Pacu have two rows of square teeth, presumably for crushing fruits and seeds.

“In modern piranhas the teeth are arranged in a single file,” said Wasila Dahdul, a visiting scientist at the National Evolutionary Synthesis Center in North Carolina. “But in the relatives of piranhas – which tend to be herbivorous fishes – the teeth are in two rows.”

The new fossil shows an intermediate pattern: teeth in a zig-zag row. This suggests that the two rows in pacu were compressed to form a single row in piranhas. “It almost looks like the teeth are migrating from the second row into the first row,” said John Lundberg, curator at the Academy of Natural Sciences in Philadelphia and a co-author of a study of the jawbone.