Introduction: A breakthrough in the history of feeding
A University of Michigan scientist and colleagues have uncovered what may be the earliest evidence of a tongue-like biting structure in a ray-finned fish. Dating to about 310 million years ago, during the early Pennsylvanian period, the fossil belongs to the genus Platysomus. This discovery marks a pivotal moment when fish began using their gill bones to modify how they capture and process food, shifting away from purely crushing prey with teeth toward a more integrated, tongue-like mechanism.
Platysomus, a deep-bodied, flat-shaped fish, belonged to the diverse ray-finned lineage that includes modern species such as goldfish and tuna. The new finding shows that this ancient group developed a plate of teeth anchored by jointed bones on the floor of the mouth. When pressed against an upper plate of teeth, this tongue-like bite could crush and grind hard prey, revealing a previously unknown level of functional complexity in early ray-finned fish.
What is the tongue-bite apparatus?
The researchers describe a “tongue bite” apparatus that involves a lower, tooth-bearing plate resting on the tongue floor and articulating with upper teeth. In Platysomus, the arrangement allowed precise grinding against upper tooth plates, effectively increasing the fish’s ability to exploit hard-shelled prey. The finding represents the earliest known instance of this specialized feeding structure, illuminating how jaw and gill bone anatomy could be repurposed to expand dietary options.
How the discovery was made
Led by paleontologist Matt Friedman of the U-M Museum of Paleontology, the team examined fossil material in museum collections, including a key Platysomus head that had survived burial in a way that preserved internal structures. The fossil’s flat, deep body often complicates reconstruction; however, three-dimensional, well-preserved head fragments offered a rare view into the internal skeleton. The researchers used CT scanning to visualize hidden features in three dimensions, a technique that can reconstruct delicate connections without destroying the specimen.
In a collaboration spanning museums in the United Kingdom and the United States, digital dissections of flattened Platysomus fossils revealed the telling tooth plates that define the tongue bite. The discovery was published in Biology Letters and supported by the U.S. National Science Foundation, underscoring how modern imaging and archival collections can yield new knowledge from long-stored specimens.
Why this matters for evolutionary biology
The Platysomus finding offers a concrete example of convergent evolution — where different lineages independently evolve similar solutions to common problems. Friedman notes that while this tongue-like biting structure arose in Platysomus, later fish groups discovered the same functional solution through parallel evolutionary pathways. Studying these repeated patterns helps biologists map the constraints and opportunities that guide evolutionary change, revealing that certain feeding challenges may funnel evolution toward particular mechanical solutions.
Tracking how different fish lineages solved similar problems—such as grinding hard prey with tooth plates and gill-supported structures—can reveal broader patterns in the origins of feeding innovations. The Platysomus study also emphasizes the value of looking beyond obvious fossils; three-dimensionally preserved heads can carry crucial inside information that is lost in more common, flatly fossilized specimens.
Context and future directions
“Tongue bite” shows how ancient fish used existing anatomical blocks in new ways, a concept relevant to many modern predators. Among living fish with biting plates, bonefish offer a distant analog in their hard-prey diet, linking ancient strategies to modern feeding ecologies. The research team emphasizes that revisiting old fossils with new technology can unlock forgotten chapters in the story of evolution, often hiding in plain sight in museum collections accumulated over generations.
Conclusion: A new chapter in the story of fish evolution
The discovery of a tongue-like biting mechanism in Platysomus not only extends the timeline of feeding innovations but also reinforces a core lesson of evolutionary biology: similar ecological pressures can drive strikingly convergent solutions across time and lineage. As imaging techniques and data from old collections continue to evolve, more of the deep history of animal adaptation awaits discovery.
