Deep beneath the surface of Carboniferous rocks in Staffordshire, England, scientists uncovered a fossil that at first glance looked like an ordinary fish. But when researchers peered inside using high-resolution CT scanning, they found something extraordinary—teeth not just in the jaws, but deep inside the mouth.
This fossil belonged to Platysomus parvulus, a ray-finned fish that lived over 310 million years ago. What set it apart was its unusual way of eating. Instead of relying only on its jaws, it had a second biting mechanism known as a “tongue bite.” This discovery pushed back the timeline of this feeding adaptation by more than 150 million years, making it the earliest known example of such a system in fish.
What at first seems like a curious quirk of anatomy turns out to be a profound window into evolution itself—a glimpse at how ancient life recovered and reinvented itself after one of Earth’s great extinction events.
The Tongue Bite: A Second Mouth Within a Mouth
Most of us imagine fish snapping at prey with their jaws, and for the majority of species, that’s true. But the tongue bite is different. It’s a clever arrangement where opposing sets of teeth—one on the roof of the mouth and another attached to the gill skeleton—work together like hidden pincers. When the fish pressed these plates together, they could crush and grind tough prey, such as shells, insects, or armored invertebrates.
Think of it as a second mouth inside the first, designed to handle food that jaws alone could not. In modern times, this adaptation can still be seen in species like trout and bonefish, where it allows them to expand their diets and thrive in varied environments. But for Platysomus parvulus, it was an innovation millions of years ahead of its time.
Evolution After Catastrophe
To understand why this matters, we need to travel further back—about 359 million years ago—to the End-Devonian Mass Extinction. This cataclysm wiped out countless species of fish, dramatically reshaping ecosystems. For those that survived, the world was open for experimentation.
Lead researcher Prof. Sam Giles of the University of Birmingham explains it this way: “After this extinction event, fish started to change and develop new body shapes and ways of feeding.” In other words, nature was reinventing itself. The discovery of a tongue-biting mechanism in Platysomus shows just how bold evolution could be in this new era.
The tongue bite was not a one-time invention. It evolved multiple times in different groups of fish, a sign of its evolutionary usefulness. It offered versatility, a chance to eat what others could not, and ultimately, a better shot at survival.
A Fossil Frozen in Three Dimensions
Fossils are often crushed flat by the immense pressure of rock, but the Platysomus specimen was preserved in 3D, a rare gift to paleontology. This allowed researchers to digitally dissect its mouth and reconstruct its anatomy in unprecedented detail.
What they saw was a sophisticated system in its early stages of development. The lower plate was made of several parts, lined with a single layer of pointed teeth, while the upper plate was narrower but matched to fit. Together, they formed a primitive but effective tongue bite system.
This places Platysomus in a fascinating position: a transitional form between simple jawed fish and later species like Bobasatrania, which had fully developed tongue bites and relied almost entirely on them to crush prey. As co-author Dr. Matthew Kolmann from the University of Louisville put it, “Platysomus parvulus is like a missing link between simple jawed fish and more advanced tongue-biters.”
Evolutionary Innovation in Action
What makes this discovery so compelling is not just the anatomy of one fish, but what it represents in the grand story of evolution. After mass extinction, the survivors are not merely remnants—they are pioneers. In the case of ray-finned fish, they began experimenting with new ways to live, move, and eat.
Prof. Matt Friedman of the University of Michigan emphasized this broader context: “Tongue bites are just one of many feeding innovations that emerged during this time. This fish represents a key evolutionary step and helps us understand how ancient ecosystems functioned and how modern fish lineages came to be.”
In other words, this single fossil captures a moment of evolutionary creativity, when life was reshaping itself to meet the challenges of a transformed world.
Why It Matters Today
It may seem like an obscure detail from deep time, but discoveries like this ripple outward, shaping our understanding of life itself. The tongue bite mechanism illustrates how survival depends not only on strength or size but on innovation. By developing new ways of eating, Platysomus and its kin opened doors to ecological niches that others could not enter.
The lesson is timeless. Evolution favors those who adapt, who find new strategies to thrive. The same principle that allowed a small fish in ancient seas to crush hard-shelled prey is the same principle that guides life’s resilience in the face of change.
For scientists, the fossil is also a reminder of how much is left to uncover. Each new discovery adds depth to our picture of the past, but also reveals gaps in our knowledge. How many other feeding strategies were tried and lost in evolutionary history? What other hidden innovations await discovery in rocks beneath our feet?
A Glimpse Into Deep Time
Standing before the fossil of Platysomus parvulus, one can imagine the ancient seas of the Carboniferous period. Dense forests towered on land, insects the size of birds buzzed through the air, and in the waters, this small but extraordinary fish tested out a new way of eating. It had no way of knowing that its tongue bite was an evolutionary gamble that would echo through hundreds of millions of years.
Today, as we peer into its fossilized mouth, we are reminded of evolution’s creativity and resilience. From catastrophe, life reinvented itself. From simple jaws, a second set of teeth emerged. From a single fossil, we glimpse not only the anatomy of an ancient fish but the restless ingenuity of life itself.
In the end, this discovery is not just about a fish with unusual teeth. It is about the story of survival and adaptation, the endless experimentation of evolution, and the way even the smallest details of a fossil can reshape our understanding of the history of life on Earth.
More information: Sam Giles et al, Tongue bite apparatus highlights functional innovation in a 310-million-year-old ray-finned fish, Biology Letters (2025). royalsocietypublishing.org/doi … .1098/rsbl.2025.0270
On bioRxiv: DOI: 10.1101/2025.05.10.653277
