In the murky waters of a world long past, some 310 million years ago, a remarkable fish evolved a surprisingly sophisticated and deadly method for dispatching its prey. This ancient creature, a ray-finned fish known as Platysomus parvulus, developed what scientists have termed a "tongue bite," a hidden second set of jaws that has rewritten our understanding of vertebrate evolution. The discovery of this unique feeding mechanism in a fossil from the Carboniferous period provides a fascinating glimpse into the experimental nature of life following a mass extinction.
A Window into a Lost World
The story of this ancient predator begins not in the water, but in the rocks of Staffordshire, UK, where its fossilized remains were unearthed. The fossil dates back to the Carboniferous period (359–299 million years ago), an era famed for its vast, lush coal forests and a burgeoning of new life forms. During this time, the Earth's landmasses were coalescing into the supercontinent of Pangea, and the climate in regions like present-day Europe was hot and humid. The environment was a dynamic one, with fluctuating sea levels creating a mosaic of forested swamps, river channels, and shallow seas.
This was a world teeming with life. Giant insects, such as dragonflies with wingspans of up to two feet, filled the air, while on land, early amphibians were becoming dominant and the first reptiles were beginning to emerge. The seas were no less dynamic, with new groups of sharks and bony fishes evolving to fill the ecological niches left vacant by the late Devonian extinction. It was in this crucible of evolutionary innovation that Platysomus parvulus carved out its existence.
The Anatomy of a Killer "Tongue"
What makes Platysomus parvulus so extraordinary is not its outward appearance, but the hidden mechanism within its mouth. Unlike most fish that rely solely on their primary jaws for feeding, this deep-bodied fish possessed a second set of teeth located on the floor and roof of its mouth. This "tongue bite" apparatus consisted of a multipartite tooth plate on its gill skeleton, which opposed another tooth field on the roof of its mouth. This arrangement effectively created a second jaw, allowing the fish to crush and process hard-shelled prey like insects and crustaceans.
The discovery was made possible by the exceptional three-dimensional preservation of the fossil, which allowed an international team of scientists to use high-resolution computed tomography (CT) scans to digitally reconstruct its internal anatomy. These scans revealed the intricate details of the opposing tooth plates, providing the earliest known evidence of such a feeding mechanism in a ray-finned fish. This discovery pushes back the origin of the tongue bite by an astonishing 150 million years.
An Evolutionary Stepping Stone
The tongue bite of Platysomus parvulus is not just a biological curiosity; it represents a key evolutionary step. Scientists believe it served as a transitional stage between simpler jawed fish and more advanced "tongue-biters." Unlike some later fish that would come to rely entirely on their tongue bite for feeding, Platysomus parvulus still used its primary jaws. This dual system likely gave it greater versatility in its feeding strategies, allowing it to consume a wider variety of foods and adapt to different environmental conditions.
Professor Sam Giles of the University of Birmingham, the lead author of the study, explains that "tongue bites have evolved many times in different fish groups – including in modern ones such as trout and bonefish, demonstrating that it is a useful tool that helps fish eat a wider variety of food and survive in different environment."
The evolution of this mechanism is seen as a response to the ecological opportunities that arose after the End-Devonian Mass Extinction. This event wiped out many marine species, paving the way for the diversification of the survivors. As co-author Professor Matt Friedman from the University of Michigan notes, "Tongue bites are just one of many feeding innovations that emerged during this time."
A "Missing Link" in Fish Evolution
Dr. Matthew Kolmann from the University of Louisville, another co-author of the study, describes Platysomus parvulus as "like a missing link between simple jawed fish and more advanced tongue-biters.” This is because later fish, such as the Bobasatrania group, developed more advanced tongue bites and lost the use of their primary jaws for chewing, instead relying on them to control water flow.
The anatomy of Platysomus parvulus provides a snapshot of this evolutionary transition in progress. Its lower tooth plate was made of multiple pieces, and both the upper and lower plates had a single layer of pointed teeth. This suggests a more primitive form of the tongue bite, capable of gripping and piercing, but not the heavy-duty crushing seen in later species with more consolidated and layered tooth plates.
The discovery of this ancient fish and its deadly tongue bite underscores a "long-fuse" model of diversification, where evolutionary changes unfold gradually over millions of years. It highlights how even in the deep past, the fundamental principles of evolution—adaptation, innovation, and the filling of ecological niches—were shaping the incredible diversity of life we see today. The story of Platysomus parvulus is a testament to the fact that sometimes, the most significant evolutionary leaps happen deep within the mouths of seemingly ordinary creatures.
Reference:
- https://www.earth.com/news/fossil-reveals-earliest-tongue-bite-in-ancient-fish/
- https://cosmosmagazine.com/history/palaeontology/tongue-bite-fish/
- https://www.pbs.org/wgbh/evolution/change/deeptime/carbon.html
- https://en.wikipedia.org/wiki/Carboniferous
- https://biodiversity.ku.edu/exhibits/carboniferous
- https://pmc.ncbi.nlm.nih.gov/articles/PMC12405943/
- https://www.sciencedaily.com/releases/2025/09/250904014143.htm
- https://scienceblog.com/a-fossil-fish-with-a-tongue-bite-and-a-wider-menu-to-survive/