310-Million-Year-Old Fossil Fish Reveals Earliest Known "Tongue Bite" Mechanism

A 310-million-year-old fossilized fish unearthed in Staffordshire, England, has revealed the earliest known instance of a "tongue bite" feeding mechanism, challenging previous assumptions about the timeline of evolutionary adaptations in ray-finned fishes.

The fossil, identified as Platysomus parvulus, exhibits a unique dental arrangement with specialized teeth on both the roof and floor of its mouth. This configuration functioned similarly to a second set of jaws, enabling the fish to crush and chew tough prey such as shells or insects. Prior to this discovery, such a feeding adaptation was believed to have evolved approximately 150 million years later.

The findings, published on September 3, 2025, in the journal Biology Letters, were made possible through high-resolution CT scanning, which allowed researchers to reconstruct the internal anatomy of the exceptionally well-preserved fossil. This analysis revealed a sophisticated arrangement of tooth plates indicative of the "tongue bite" mechanism.

Lead author Professor Sam Giles from the University of Birmingham commented on the significance of the discovery:

"Our discovery helps us understand how fish evolved after the End-Devonian Mass Extinction, which wiped out many species. After this extinction event, fish started to change and develop new body shapes and ways of feeding."

The "tongue bite" mechanism involves opposing sets of teeth—one on the roof of the mouth and another on the gill skeleton—that work together to grip and crush prey. This adaptation has evolved multiple times in different fish groups, including modern species such as trout and bonefish, demonstrating its utility in enabling fish to consume a wider variety of food and survive in diverse environments.

Co-author Dr. Matthew Kolmann from the University of Louisville noted the transitional nature of P. parvulus:

"Later fish, like the Bobasatrania group, had more advanced tongue bites and did not use their jaws at all, relying on their tongue bite to crush hard food. Platysomus parvulus is like a missing link between simple jawed fish and more advanced tongue-biters."

The fossil was discovered in Carboniferous rock formations in Staffordshire, UK. Its exceptional three-dimensional preservation allowed researchers to employ high-resolution CT scanning to reconstruct its internal anatomy, revealing a sophisticated arrangement of tooth plates.

This discovery provides new insights into the rapid experimentation with feeding strategies by fish following mass extinction events, particularly after the End-Devonian Mass Extinction. The study supports a model of rapid innovation in early ray-finned fishes during this period, highlighting the evolutionary flexibility and adaptability of these species in response to ecological challenges.

Professor Matt Friedman from the University of Michigan emphasized the broader context of feeding innovations during this period:

"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."

The study was conducted by an international research team, including lead author Professor Sam Giles from the University of Birmingham, Dr. Matthew Kolmann from the University of Louisville, and Professor Matt Friedman from the University of Michigan. The research was supported by the Royal Society, the National Science Foundation, and the Natural Environment Research Council.

The discovery of Platysomus parvulus and its unique feeding mechanism not only challenges existing timelines of evolutionary adaptations but also underscores the importance of continued paleontological research in uncovering the complexities of ancient life forms and their ecosystems.