Palaeoniscum
Palaeoniscum (from , 'ancient' and 'cod-fish' or 'woodlouse') is an extinct genus of ray-finned fish from the Permian period (Guadalupian-Lopingian) of England, Germany, Turkey, North America and Greenland, and possibly other regions. The genus was named Palaeoniscum in 1818 by Henri Marie Ducrotay de Blainville, but was later misspelled as Palaeoniscus by Blainville and other authors (notably Louis Agassiz). Palaeoniscum belongs to the family Palaeoniscidae. The type species Palaeoniscum freieslebeni was named after Johann Carl Freiesleben (1774–1846), mining commissioner of Saxony. P. freieslebeni is the most common taxon in the Wuchiapingian aged Kupferschiefer and Marl Slate, where it constitutes 80% of all fish fossils. The genus is considered to be a poorly defined wastebasket taxon. Palaeoniscum had a torpedo-shaped body in length, with a deeply forked caudal fin and tall dorsal fin, indicating that it was a fast swimmer. It was probably an active predator, feeding on other freshwater fish. Its sharp teeth could be replaced when lost, a trait also seen in modern sharks. Like other early ray-finned fish, Palaeoniscum had air sacs connected to the mouth, which served as a primitive swim bladder. Several Palaeozoic and Mesozoic species that have been ascribed to the genus Palaeoniscum were later