Canobius is an extinct genus of early ray-finned fish that lived in the Carboniferous period of Europe. Canobius was a small fish, 7 centimetres (3 in) in length. Compared with its earlier relatives, it had specialized jaw bones and hyomandibulars which attached the upper jaw to the brain case, meaning that the jaws were hung vertically under the brain case. This allowed Canobius to open its jaws wider and expand its gill slits further at the same time. In turn this meant that the fish could take in more oxygen, making it a more active creature. Canobius is presumed to have fed on plankton which it filtered from the water using its small teeth and gills.