For hundreds of millions of years, sharks have been swimming the seas, eviscerating hapless prey with their terrifying, dagger-like teeth. But when face to face with most other fish, you might be a bit flummoxed to find a serrated smile.
Today, in the journal Current Biology, researchers at the Jura Museum in Eichstätt, Germany report the discovery of an ancient, previously unknown fossil fish that bears an uncanny resemblance to the modern freshwater piranha—à lasome razor-sharp dentition. If confirmed, this ferocious-looking fish may join an exclusive club of ancient marine flesh-eaters, defying dietary norms of the Jurassic sea and beyond.
Researchers first unearthed the unusual fossil in 2016 from the Late Jurassic Plattenkalk quarry of Ettling in Bavaria, Germany. Sporting a flat, disc-like body, the fish resembled a finned Frisbee. On the outside, the newfound fish had features that fit well with the biological order Pycnodontiformes—a group that went extinct during the Eocene Epoch, between 34 and 56 million years ago. And, at about 150 million years old, it fell in neatly within the timeline of when these fish would have thrived. But as lead author Martina Kölbl-Ebert chiseled away the surrounding debris, she was “completely flabbergasted” to find that the fossilized fish’s run-of-the-mill characteristics ended abruptly at its jaw.
Peer inside the mouth of your average pycnodontiform, and you’ll find a cobblestone path: an uneven surface dotted with flat, docile dentition, ideal for cracking open hard-shelled prey like sea urchins. Even the best armored of these little marine creatures were no match for the might of pycnodontiform jaws.
But the teeth of this particular specimen were far better suited to break rules than shells. Unlike its brethren, this fossil lacked the thick, blunt teeth—or, loosely, pycnodonti—so ubiquitous across pycnodontiforms that they gave rise to the group’s scientific name. In their stead were several ghastly fangs.
“It was like encountering a sheep with a wolf’s snarl,” says Kölbl-Ebert of the prehistoric piranha lookalike. Piranhas and pycnodontiforms are completely unrelated, but to Kölbl-Ebert, the similarities in this fossil were too striking to ignore. To honor its modern doppelgänger, she and her team named their new find Piranhamesodon pinnatomus—essentially, “piranha-like fin-cutter.”
The upper half of P. pinnatomus’ jaw featured long, curving scythes, baring down to meet a shorter set of triangular, serrated daggers below. And, according to Kölbl-Ebert, P. pinnatomus probably packed a powerful bite. Pairing brute force with its considerable chompers, P. pinnatomuswas literally armed to the teeth.
With such daunting dentition, Kölbl-Ebert reasons that P. pinnatomus might just have had a taste for fresh, fishy flesh. But other researchers are less certain it was chowing on live prey.
“It’s neat to see such a rare fossil, and these fish are definitely oddballs,” says Matthew Kolmann, an evolutionary ecologist who studies fish morphology at George Washington University. “But with any sort of dead thing, especially for something that’s been dead for 150 million years, it’s hard to really figure out what it was doing.”
In spite of its ghastly grin, P. pinnatomus doesn’t really fit the bill of a voracious marine predator. For one, its teeth are tiny—no more than a millimeter or so in length. According to Lisa Whitenack, who studies the biomechanics of shark and other fish teeth at Alleghany College, these mini machetes would be hard-pressed to truly julienne chunks of flesh.
What’s more, P. pinnatomus doesn’t quite have the physique of a professionalflesh-eater. Carnivorous piranhas, for instance, ripple with muscles built for bursts of speed—crucial assets when on the hunt. With its round, stout frame, P. pinnatomuslooks to be more of the slow and steady type—traits probably incompatible with sneaking up on other fish, says Francisco Poyato Ariza, a paleontologist who studies fish evolution at the Autonomous University of Madrid in Spain.
And P. pinnatomus teeth aren’t exclusively spiky. In fact, the teeth toward the back of its jaw plateau in shapes far more reminiscent of the mortar and pestle strategy of other pycnodontiforms, says Stephanie Crofts, who has studied the dentition of extinct piranha ancestors (actual ones this time). But this fish was no nibbling ninny. Even at their size, Crofts adds, the fangs at the front of P. pinnatomus’ mouth probably had at least some slicing and dicing capabilities.
“[Its teeth] actually look multifunctional,” Crofts explains. “Maybe it’s a flesh-tearing monster, but maybe it’s a pycnodontiform that’s decided to expand its options.”
Even P. pinnatomus’ piranha namesakes eat a much more balanced diet than you might think: According to Kolmann, piranhas are mere opportunists who are more or less happy to eat anything that floats—or swims—past. A couple species have even turned to subsisting almost entirely on leaves and the occasional insect, and just haven’t yet lost their signature snarl (though one of the piranha’s closest relatives, the plant-eating pacu, boasts some mind-bendingly humanoid teeth).
“If I’d found this specimen, I wouldn’t have thought it was a flesh-eater,” Jürgen Kriwet, a fish morphology expert at the University of Vienna, says of the new fossil. “The teeth would be useful in grabbing and holding prey, but not to tear flesh out of other fish… [to me], it looks like an omnivore that exploits different food resources.”
Kölbl-Ebert, however, is fairly convinced her catch was a carnivorous connoisseur, pointing out that some of P. pinnatomus’ blunter teeth may have been too fragile to do much crushing. What’s more, a couple of ray-finned fishes—a broad group that includes pycnodontiforms—may have munched on other fish long before and long after P. pinnatomus, explains Jennifer Lane, a paleontologist at the American Museum of Natural History.
To chip away at the dietary mystery, Kölbl-Ebert and her team foraged through nearby limestone for remains from meals past. To their amazement, they discovered several unrelated fishes whose fins looked as though they’d sustained some damage. If P. pinnatomus was responsible, it may have been the cleverest of moves: Webbed appendages such as fins—unlike internal organs—can grow right back after they’ve been wounded, making this fossil fish a potential early advocate for sustainable eating.
But even clipped fins don’t necessarily incriminate P. pinnatomus as a gore gourmand. Fins are fragile and easily lost to the process of fossilization or excavation—without a time machine, Whitenack says, researchers can’t know how those bits and pieces were ultimately chipped away.
Finding fins in the stomach of one of these fish, Kolmann adds, would be far more definitive. But in the many, many decades that the limestone quarry in Ettling has been an excavation site, only one P. pinnatomus has been found, Kölbl-Ebert says, and sadly, its stomach was empty.
Until another of its kind surfaces, it may remain unclear whether P. pinnatomus was truly a first in flesh eating.But whatever this freaky fish was noshing on, it’s clear the scaled specimen was like nothing else in the Jurassic sea.
“These guys have teeth on teeth on teeth,” Crofts laughs. “Ultimately, it’s pretty cool how they’ve managed to wrangle these once-flat sheaths of teeth into what looks to be a pretty nasty set of chompers.”