Leptolepis

Leptolepis (from λεπτός leptós, 'slight' and λεπίς lepis 'scale') is an extinct genus of stem-teleost fish that lived in what is now Europe during the Jurassic period (Toarcian–Callovian ages).

Taxonomy
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. Other species were reassigned to different genera.


 * Leptolepis autissiodorensis Sauvage, 1892
 * Leptolepis buttenheimensis Schwarzhans & Keupp, 2022
 * Leptolepis coryphaenoides (Bronn, 1830)
 * Leptolepis curvisulcatus Schröder, 1956
 * Leptolepis jaegeri Agassiz, 1832
 * Leptolepis kremmeldorfensis Schröder, 1956
 * Leptolepis inaequalis Weiler, 1954
 * Leptolepis nathorsti Woodward, 1900
 * Leptolepis macrocephalus Schröder, 1956
 * Leptolepis normandica Nybelin, 1962
 * Leptolepis saltviciensis Simpson, 1855
 * Leptolepis steberae Schwarzhans & Keupp, 2022
 * Leptolepis woodwardi Nybelin, 1974

Species formerly placed in Leptolepis
The type species Leptolepis coryphaenoides is placed as a stem-group Teleost.
 * Leptolepis talbragarensis Woodward, 1895 (Now referred to Cavenderichthys)
 * Leptolepis koonwarri Waldman, 1971 (Now referred to Waldmanichthys)

Cladogram of Teleosteomorpha after Sferco et al. 2021:

Appearance
Length of Leptolepis was about 8.5 cm long, and superficially resembled the unrelated modern herring. While more basal teleosts such as Pholidophorus had skeletons composed of a mixture of bone and cartilage, Leptolepis resembled modern teleosts in possessing a skeleton completely made of bone. Another modern development in Leptolepis were its cycloid scales, which lacked the covering of ganoine present in more basal teleosts. These two developments made swimming easier, as the bony spine was now more resistant to the pressure caused by the S movements made while swimming.

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. Pelagosaurus was a known predator of Leptolepis, as a Pelagosaurus fossil was found with Leptolepis remains in its stomach. Clarkeiteuthis is known from three specimens with Leptolepis in its arms, which estimate that Leptolepis is probably most common prey of Clarkeiteuthis.

The Morrison cf. Leptolepis
Known only from a single nearly complete skeleton found at Rabbit Valley, Colorado. A 13 cm fish that was deeper bodied than its co-occurring contemporaries Morrolepis and Hulettia. The Morrison cf. Leptolepis probably had a live mass of about 37 g. It is the only teleost fish known from the formation and was morphologically more highly derived than other Morrison fish. A specific example of apomorphy in cf. Leptolepis is its "more modern tail structure" compared to Morrolepis. It is believed to have fed on fish and small invertebrates.