Artist’s impression of Platysomus parvulus with its tongue bite exposed. Credit: Joschua Knüppe
Imagine having an extra set of teeth on the roof and floor of your mouth. In addition to chewing with the molars on your jaw, you could also grip and crush food between these plate-like teeth.
Humans never evolved this unique ‘tongue bite’ approach, but lots of different fish have to crush and chew shelled or insect prey.
“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,” says Sam Giles, a professor of palaeobiology at the University of Birmingham in the UK.
Giles is lead author of a new study which has uncovered the earliest known fish to have evolved this extra set of teeth. The 310-million-year-old fossilised ray-finned fish, Platysomus parvulus, was discovered in the UK county of Staffordshire.
Before now, the oldest known tongue biting fish lived 150 million years later.
The new fossil was preserved in 3 dimensions, which allowed researchers to use high-resolution computed tomography (CT) scans to reconstruct its internal anatomy.
This revealed the opposing sets of teeth: a narrow and relatively flat plate on the roof of the mouth and 2 rows of 3 separate but tightly packed plates on the lower ‘gill skeleton’.
It also had a set of teeth on its jaws and likely used both to increase the versatility of its feeding strategies.
Co-author Dr Matthew Kolmann from the University of Louisville, USA, adds: “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.”
Evolution of a tongue bite in a lineage of Palaeozoic–Mesozoic actinopterygians, showing upper (purple) and lower (green) tooth plates. Credit: Giles, Kolmann and Friedman 2025, Biology Letters
The new fossil dates to the Carboniferous period (359–299 million years ago) which is named after the coal deposits formed at the time. The period was preceded by the Devonian and was followed by the Permian.
“Our discovery helps us understand how fish evolved after the End-Devonian Mass Extinction, which wiped out many species,” says Giles.
“After this extinction event, fish started to change and develop new body shapes and ways of feeding.”
Co-author Matt Friedman, a professor at the University of Michigan in the US, adds: “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 research is published in the journal Biology Letters,