Megapiranha 3-foot Piranha Fossil
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.
Another close relative of the piranha, called pacu (singular and plural), is not so scary. Pacu have squared-off stumps of teeth used for munching veggies. (For the record, tales of carnivorous piranhas eating humans are fictional.)
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.
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.
If this is so, Megapiranha may be an intermediate step in the long process that produced the piranha’s distinctive bite. To find out where Megapiranha falls in the evolutionary tree for these fishes, Dahdul examined hundreds of specimens of modern piranhas and their relatives.
The Megapiranha fossil was originally collected in a riverside cliff in northeastern Argentina in the early 1900s, but remained unstudied until paleontologist Alberto Cione of Argentina’s La Plata Museum rediscovered the startling specimen — an upper jaw with three unusually large and pointed teeth — in the 1980s in a museum drawer.