![\"An](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14229e-Platysomus-parvulus.jpg\")
<\/a><\/p>\nAn artist\u2019s impression of Platysomus parvulus. Image credit: Joschua Kn\u00fcppe.<\/p>\n
Platysomus parvulus lived at the beginning of the Pennsylvanian subperiod of the Carboniferous period, 310 million years ago, at a time when a group of fish called ray-finned fish were exploring new ways to make a living.<\/p>\n
The species had a plate of teeth suspended by a cradle of jointed bones that also supported the gills it used to breathe.<\/p>\n
The plate of teeth, situated on the floor of the mouth like a tongue, was in direct opposition to a plate of teeth above it, and the fish used the plates to crush and grind food.<\/p>\n
As it turns out, this ancient fish was the first to evolve this feeding structure called a tongue bite.<\/p>\n
Until now, the oldest known fish with such a dental arrangement lived about 150 million years later.<\/p>\n
\u201cOne of the most powerful things we have for understanding evolution is adaptation,\u201d said Dr. Matt Friedman, a paleontologist at the University of Michigan\u2019s Museum of Paleontology and the Natural History Museum, London.<\/p>\n
\u201cWe can see that different kinds of creatures can adjust to similar kinds of demands in different ways.\u201d<\/p>\n
\u201cBut in this case, this is cool because it\u2019s showing us a convergent adaptation.\u201d<\/p>\n
\u201cThis extinct group of fishes discovered this trick, and actually, it turns out that many different groups of fishes figured out this trick at later times.\u201d<\/p>\n
\u201cAfter multiple times, that tells us a little bit about what the constraints on evolutionary change might be, or if there are pathways that are easier to evolve along than others.\u201d<\/p>\n
The Platysomus parvulus fossil was discovered in Carboniferous rock formations in the UK county of Staffordshire.<\/p>\n
Dr. Friedman and his colleagues used high-resolution CT scanning to reconstruct the internal anatomy of the specimen.<\/p>\n
They were surprised to see a series of well-developed tooth plates inside the mouth of the animal.<\/p>\n
\u201cThey\u2019re deep-bodied animals. They look a little like an angel fish,\u201d Dr. Friedman said.<\/p>\n
\u201cBut not only were they flat in life, they\u2019re typically squished even more flat as fossils.\u201d<\/p>\n
\u201cSo although whole fossil fish skeletons are common, it\u2019s often hard to extract details of the internal skeleton. Fossils probably preserve those parts, but they\u2019re deadly flat.\u201d<\/p>\n
\u201cOur discovery helps us understand how fish evolved after the end-Devonian mass extinction, which wiped out many species,\u201d said Professor Sam Giles, a paleontologist at the University of Birmingham.<\/p>\n
\u201cAfter this extinction event, fish started to change and develop new body shapes and ways of feeding.\u201d<\/p>\n
\u201cTongue bites have evolved many times in different fish groups \u2014 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 environments.\u201d<\/p>\n
\u201cLater 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,\u201d said Dr. Matthew Kolmann, a paleontologist at the University of Louisville.<\/p>\n
\u201cPlatysomus parvulus is like a missing link between simple jawed fish and more advanced tongue-biters.\u201d<\/p>\n