Leptolepis ("delicate scale") is an extinct genus of teleost fish that lived freshwater and marine environments from the Middle Triassic period until the Early Cretaceous. The genus is one of the earliest recognized teleost genera.
An average individual of Leptolepis was about 30 centimetres (12 in) long, and superficially resembled the unrelated modern herring. It was the first true bony fish to really live up to the name, possessing a skeleton completely made of bone; some previous genera such as Pholidophorus had skeletons composed of bone and cartilage. Another modern development in Leptolepis were its scales, which lacked the covering still present in previous genera. 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.
The Land Before Time
In The Land Before Time V: The Mysterious Island, a school of Leptolepis is briefly seen swimming in the ocean.