A fossil discovery from roughly 310 million years ago is reshaping how scientists understand the evolution of feeding in ray-finned fish. The fossilized remains of Platysomus, an early Pennsylvanian fish, show the first clear evidence of a tongue-like biting structure that used gill bones to crush and grind prey. This tiny but pivotal innovation demonstrates how early ray-finned fishes experimented with new feeding strategies and convergent adaptations that would echo across millions of years of evolution.
A 310-Million-Year-Old Discovery
The study, published in Biology Letters by a team led by paleontologist Matt Friedman of the University of Michigan, identifies a distinctive set of tooth plates anchored by jointed bones. This palate-ward arrangement sat on the floor of Platysomus’ mouth and pressed against a second tooth plate higher up. In effect, the fish could bite and grind its prey using a tongue-like action powered by its own gill arches. The team concludes that Platysomus represents the earliest known instance of this specialized feeding mechanism, now termed a tongue bite.
How the Tongue Bite Works
Biologist and paleontologist Friedman explains that the teeth plates formed a lever-like system. When opened and closed, the lower plate pressed against the upper plate, crushing hard-shelled prey such as crustaceans or other armored foods. The discovery is notable not only for identifying a novel feeding tactic but also for showing how ancient fish could reuse existing skull and gill-bone structures to solve new ecological challenges.
The Role of Platysomus in the Evolutionary Puzzle
Platysomus itself was a deep-bodied, flat-bodied ray-finned fish, a creature that lived around the Pennsylvanian period. Its body plan, while efficient for its lifestyle, posed challenges for fossil preservation, particularly for internal anatomical details. Friedman notes that the fossil record often yields flat perspectives that obscure inner skeletons. The tongue-bite feature, now visible in three-dimensions thanks to modern imaging, provides a rare glimpse into internal feeding adaptations and how they could arise in parallel across different lineages.
Why 3D Imaging Matters
The researchers used CT scanning to examine three-dimensional Platysomus heads in museum collections. These uncrushed or minimally crushed specimens preserve internal structures that are usually hidden in flattened fossils. The digital dissections revealed the jaw-to-tooth-plate arrangement and the intimate relationship between tooth plates and gill-supporting bones—an arrangement that would be nearly impossible to detect with conventional fossil study alone.
Convergent Evolution and Evolutionary Pathways
The tongue-bite arrangement seen in Platysomus highlights a broader theme in evolutionary biology: convergent evolution. Friedman emphasizes that different groups of fishes arrived at similar functional solutions to feeding problems, suggesting certain constraints or accessible evolutionary pathways. Later, other fish lineages would independently develop comparable tooth-plate systems as they faced hard-shelled prey. This pattern helps scientists map how and why certain design solutions recur, revealing underlying rules that govern evolutionary change.
Broader Impact and Ongoing Questions
Beyond the specifics of Platysomus, the discovery underscores the value of museum collections and re-examining old specimens with new technologies. The key fossil that anchored the study was likely collected over a century ago and had not attracted much attention until now. As more fossils are reanalyzed with 3D imaging and other modern methods, scientists expect to uncover additional instances of early feeding innovations that illuminate the pathways of fish evolution and the diverse solutions natural selection can produce.
Publication and Acknowledgments
The findings appear in Biology Letters in a study by Sam Giles, Matthew Kolmann, and Matt Friedman and were supported by the U.S. National Science Foundation. This work contributes to a growing understanding of how ancient fishes negotiated their ecological world and how their descendants navigated the complex landscape of evolutionary change.
