Sharks are in the ocean, piranhas are in freshwater, and that's the way it's always been … right? Well, it turns out that 150 million years ago, the sea was also home to a very piranha-like fish known as Piranhamesodon pinnatomus. The recently-classified creature is officially the earliest known flesh-eating ray-finned fish.

Originally discovered in limestone deposits in the Solnhofen region of southern Germany, the fossilized remains of one of the fish ended up in the collection of the Jura-Museum in the German town of Eichstätt. Now, an international team of scientists has declared it a previously-unknown species.

It had long, pointed teeth which were located on the exterior of the vomer (a bone which forms the roof of the mouth) and at the front of the upper and lower jaws, plus it sported triangular teeth with serrated edges along the sides of the lower jaw, on the prearticular bones. Additionally, the combined pattern of all the teeth, along with the shape and mechanics of the jaws, strongly suggest that it fed by slicing flesh as opposed to swallowing prey whole.

Like the modern-day (but apparently unrelated) piranha, it is thought to have mainly eaten the fins of other fish, without killing them. A clever strategy, in that those fins continually grow back, ensuring an ongoing food supply. In fact, the fossilized remains of other types of fish from the same deposit were found to have nipped-off fins.

Interestingly, it belonged to the Pycnodontiformes order, the other members of which were known for having flat teeth – not sharp ones – that would have been good for crushing hard-shelled invertebrates. It had previously been thought that bony fish (as opposed to sharks, which have cartilaginous skeletons) didn't start feeding by flesh-slicing until much later in prehistory.

"The new finding represents the earliest record of a bony fish that bit bits off other fishes, and what's more it was doing it in the sea," says David Bellwood of Australia's James Cook University. "So when dinosaurs were walking the earth and small dinosaurs were trying to fly with the pterosaurs, fish were swimming around their feet tearing the fins or flesh off each other."

A paper on the research, which also involved scientists from the Jura-Museum and Germany's Friedrich-Alexander University, was recently published in the journal Current Biology.

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