Unveiling the Tongue-Bite: A 310-Million-Year Innovation
A recent study by a University of Michigan-led team reveals the earliest known tongue-like biting structure in an ancient fish. The species, Platysomus, lived about 310 million years ago during the Pennsylvanian period, a time when ray-finned fishes were experimenting with new feeding strategies. The discovery shows that these early fishes could press one plate of teeth against another using gill-supporting bones, effectively crushing and grinding hard prey. This adaptation, now called the tongue bite, marks a pivotal moment in how fish evolved to process food and extract nutrients from tough prey items.
Platysomus: The Flat-bodied Explorer of the Pennsylvanian Seas
Platysomus belonged to the ray-finned lineage that still dominates many modern oceans. Its name, meaning flat-bodied, reflects its deep, compressed form. Fossils of Platysomus are challenging to analyze because their flat bodies complicate the visibility of internal structures. In life, the fish was well-adapted to its environment, but fossilization often renders its inner anatomy obscure. Modern imaging, however, is helping paleontologists peer inside and reconstruct how this ancient creature fed.
How the Discovery Was Made
The breakthrough came when researchers CT-scanned three-dimensionally preserved Platysomus heads housed in a museum. In one unusually intact specimen, scientists found an articulate setup of tooth plates anchored by jointed bones that also supported the gills. The lower plate sat on the mouth floor and pressed against an upper dental row, effectively performing a biting action that crushed hard prey. These internal features were difficult to discern in flattened fossils, but digital dissection revealed a functional system remarkably similar in spirit to the tongue bite seen in later fishes.
From Fossil to Function
As the team noted, the arrangement allowed Platysomus to manipulate prey with a cradle-like tongue-bite mechanism. The discovery supports the idea that feeding innovations can arise through different anatomical paths that converge on similar solutions to ecological challenges. In Friedman’s words, the finding illustrates convergent evolution: distinct lineages converge on analogous tools to tackle comparable problems, sometimes using different anatomical routes to reach the same functional goal.
Evolutionary Implications
The tongue bite in Platysomus helps scientists map patterns in the origin of tooth plates and other feeding structures across ray-finned fish. Tracking where and how similar tools appear across lineages offers clues about evolutionary constraints and the relative accessibility of certain adaptations. The researchers emphasize that this convergent trajectory—developing bite plates and analogous gill-supported mechanisms—appears multiple times through deep time, suggesting there may be limited, repeatable pathways to solving dietary challenges for early fishes.
Broader Significance and Museum Legacies
The study, published in Biology Letters and supported by the National Science Foundation, also highlights the value of museum collections. A key specimen that underpins the work was collected well over a century ago, illustrating how modern techniques can extract new data from existing material. This approach underscores a growing realization in paleontology: progress often comes from reexamining old fossils with fresh methods, rather than always seeking new field discoveries.
Looking Ahead: What This Means for Fish Evolution
Understanding how Platysomus fed sheds light on the broader evolutionary narrative of ray-finned fishes, a group that includes today’s most economically important species. The tongue-bite finding adds a piece to the puzzle of how early fishes diversified their feeding strategies, influencing our understanding of how complex jaws, teeth, and supporting structures evolved in response to ecological pressures. As researchers continue to scan uncrushed fossil heads and apply advanced imaging, more surprises from the deep past may redefine how we chart the history of fish evolution.
