[6][7][8] The genus Leptolepis was for a long time used as a wastebasket taxon for various small, unspecialised teleosts that did not form a natural clade.

In 1974 the Swedish ichthyologist Orvar Nybelin revised the genus, restricting it to seven species from the Early to Middle Jurassic of Europe.

Cladogram of Teleosteomorpha after Sferco et al. 2021:[12]Holostei Pachycormiformes Aspidorhynchiformes Mesturus Pholidophoridae Siemensichythys Dorsetichthys Eurycormus Leptolepis coryphaenoides Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes) Length of Leptolepis was about 8.5 centimetres (3.3 in) long,[13] and superficially resembled the unrelated modern herring.

[14] Another modern development in Leptolepis were its cycloid scales, which lacked the covering of ganoine present in more basal teleosts.

[15] Mass graves of Leptolepis have indicated that species probably lived in schools which would provide some protection from predators while the creatures fed on surface plankton.