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.

Like other early ray-finned fish, Palaeoniscum had air sacs connected to the mouth, which served as a primitive swim bladder.

[7] Several Palaeozoic and Mesozoic species that have been ascribed to the genus Palaeoniscum were later shown to be only distantly related with P. freieslebeni.

Palaeoniscum is the name giving taxon of the extinct Palaeonisciformes (or Palaeoniscoidei), a polyphyletic group comprising several superficially similar looking but not closely related early actinopterygian taxa.