The exquisitely preserved fossil of a strange flesh-eating bony reef fish that lived during the time of the dinosaurs has been discovered — along with some of its potential victims.

Key points: Fossil fish is the oldest-known flesh-eating fish with bony webbed fins

Fossil fish is the oldest-known flesh-eating fish with bony webbed fins It mimicked the shape of other fish so it could sneak up on them and rip bits out of their fins

It mimicked the shape of other fish so it could sneak up on them and rip bits out of their fins Even though its teeth are similar to a modern piranha, the two fish species are not related

The 150-million-year-old fish, dubbed Piranhamesodon pinnatomus, was a master of disguise.

While it looked just like other bony fish swimming in the warm, tropical seas, it had razor-sharp teeth like a piranha — perfect for ripping chunks out of its victims' fins.

It's a tactic that caught its ancient prey — and today's scientists — by surprise.

The ancient crime scene was unearthed in a quarry in southern Germany famous for its beautiful fossils of the iconic bird-like dinosaur Archaeopteryx.

The fossils of the new fish and its victims, reported today in the journal Current Biology, were found in 2016 by a team of scientists from the Jura Museum in Eichstätt.

The museum's director Martina Kölbl-Ebert said the flesh-eater, which was spotted by her co-author and husband Martin, was like nothing she had ever seen before.

"He called me and said 'look at these teeth, this is quite unusual'.

"I looked into the microscope and I was completely flabbergasted."

"That can't happen, it's like you have a chimera.

"It doesn't look like anything else I've ever seen in [this kind of fish]."

A wolf in sheep's clothing

The fish wouldn't have been the only flesh-eater swimming in the world's oceans at the time.

There were sharks that could rip pieces off their prey, and there were other fish that swallowed their prey whole.

But this is the oldest-known flesh-eating fish with bony webbed fins.

The fish, which was about 9 centimetres from tip to tail, belonged to an extinct group of bony reef fish known as pycnodontiform.

These round-shaped fish were equipped with scissor-like teeth at the front of their mouth to pick things up, and flat, pavement-like teeth in the back of their mouth designed to crunch and crush up their meal.

This is a "normal" pycnodontid called Turbomesodon relegans. Unlike the new fossil, this fish had crushing teeth. ( Supplied: Martina Kolbl-Ebert/Jura-Museum Eichstatt )

The newly discovered fish had much sharper, pointier teeth at the front and upper jaw, and triangular teeth in the lower jaw, which would have worked together like scissors.

"If you look at that [fossil] it's like having a sheep, and finding it has teeth like a lion or wolf," Dr Kölbl-Ebert said.

And it used its body shape to fool its prey.

"If you look at its fins, you get the idea it was very manoeuvrable, but very slow, so it's not a hunter," Dr Kölbl-Ebert said.

"The other fish wouldn't notice it as being dangerous, because these fish with these shapes usually go for snails and sea urchins.

"So, it would be possible to slowly approach other unwary fish, and then suddenly attack when it's already very close."

Meet its victims

The fossils of seven fish with chunks ripped out of their fins, which were excavated from the same sediment, were potentially some of its victims.

"You really see that these fish have been attacked," Dr Kölbl-Ebert said.

This ancient fish, known as Thrissops formosus, has large piece torn out of the lower lobe of its tail fin. ( Supplied: Martina Kolbl-Ebert/Jura-Museum Eichstatt )

We'll never know for sure who the culprit was, but Dr Kölbl-Ebert said it was unlikely the rips came from the two other meat cutters at the time: sharks and turtles.

"So far there is no evidence for sharks in the locality of Ettling, not even isolated teeth," she said.

"Turtles were present, however. But both, sharks and turtles, would be bigger … and it becomes more likely that any attack by them would target not just the fins, but the whole fish."

Nipping a bit out of the fins, which can regrow and regenerate, meant the fish potentially had a renewable food source.

"There's quite a lot of organic matter on those fins in the skin and muscles," Dr Kölbl-Ebert said.

Cunning predator-prey strategy

The fish had a pretty cunning predator-prey strategy, said palaeontologist John Long from Flinders University, who was not involved in the discovery.

"I love the way this thing is not built for speed — it's just a big flat round fish," Professor Long said.

"With that kind of body, you've got to be cunning to get your prey. You have to use your brain."

The strategy is similar to that used by today's piranhas, which live in freshwater rivers in South America.

But the two fish are not related.

"It's a completely different lineage — think Tassie tigers and wolves — they're not related at all, but they have a similar body shape and do a similar job as a predator," Professor Long explained.