''Leptolepis'' (from el, λεπτός , 'slight' and el, λεπίς 'scale') is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of stem-

teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tele ...

fish that lived in what is now Europe during the

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

period (

Toarcian The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian ...

–

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

ages).

Species

The genus ''Leptolepis'' was for a long time used as a

wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...

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'' * ''Leptolepis coryphaenoides'' * ''Leptolepis jaegeri'' * ''Leptolepis nathorsti'' * ''Leptolepis normandica'' * ''Leptolepis saltviciensis'' * ''Leptolepis woodwardi''

Species formerly placed in ''Leptolepis''

* ''Leptolepis talbragarensis'' (Now referred to ''

Cavenderichthys ''Cavenderichthys talbragarensis'' is a species of prehistoric bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted ...

'') * ''Leptolepis koonwarri'' (Now referred to '' Waldmanichthys'')Sferco, Emilia, Adriana López-Arbarello, and Ana María Báez. "Phylogenetic relationships of† Luisiella feruglioi (Bordas) and the recognition of a new clade of freshwater teleosts from the Jurassic of Gondwana." BMC Evolutionary Biology 15.1 (2015): 1.

Appearance

Clarkeiteuthis and Leptolepis reconstruction

Length of ''Leptolepis'' was about long, and superficially resembled the unrelated modern herring. While more basal teleosts such as '' Pholidophorus'' had skeletons composed of a mixture of

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

and cartilage, ''Leptolepis'' resembled modern teleosts in possessing a skeleton completely made of bone.The virtual petrified wood museum
/ref> Another modern development in ''Leptolepis'' were its

cycloid scale A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

s, which lacked the covering of

ganoine Ganoine or ''ganoin'' is a glassy, often multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes, such as gars, bichirs, and coelacanths. It is composed of rod-like, pseudoprism ...

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 A school is an educational institution designed to provide learning spaces and learning environments for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is sometimes compulsor ...

which would provide some protection from predators while the creatures fed on surface

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

. ''

Pelagosaurus ''Pelagosaurus'' (meaning "lizard of the open sea") is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 176 Ma (million years ago), in shallow epicontinental seas that ...

'' was a known predator of ''Leptolepis'', as a ''Pelagosaurus'' fossil was found with ''Leptolepis'' remains in its stomach. ''

Clarkeiteuthis ''Clarkeiteuthis'' is a genus of extinct belemnoid cephalopod known from the lower Jurassic in Germany and England. Described two species, ''C. conocauda'' and ''C. montefiorei'' are originally described as species of phragmoteuthid '' Phragmot ...

'' 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.Foster, J. (2007). "cf. ''Leptolepis''." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their World''. Indiana University Press. p. 135. A fish that was deeper bodied than its co-occurring contemporaries ''

Morrolepis ''Morrolepis'' is an extinct genus of prehistoric coccolepidid "palaeoniscoid" ray-finned fish that lived during the Late Jurassic and earliest Cretaceous epochs in Europe, Asia and North America. The type species is ''Morrolepis schaefferi' ...

'' and ''

Hulettia ''Hulettia'' is an extinct genus of ray-finned fish found in the Morrison Formation in the western United States, measuring approximately three to four inches in length. This fish genus contains one species, ''H. americana''. Its body was covere ...

''. The Morrison cf. ''Leptolepis'' probably had a live mass of about . 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.

References

Bibliography

* Silva Santos, R. (1958) - Leptolepis diasii, novo peixe fossil da Serra do Araripe, Brasil”. Boletim da Divisa˜o de Geologia e Mineralogia do Departamento Nacional de Produc¸a˜o Mineral, Notas Preliminares, Brazil 108, 1–15. o, Kiadó: Departamento Nacional de Produc¸a˜o Mineral. * Maisey, J.. Santana fossils, an illustrated atlas. Neptune City, New Jersey, USA: T.F.H. Publications (1991) * Silva Santos, R. (1995) - Santanichthys, novo epı´teto gene´rico para Leptolepis diasii Silva Santos, 1958 (Pisces, Teleostei) da Formac¸a˜o Santana (Aptiano), Bacia do Araripe, NE do Brasil”. Anais da Academia Brasileira de Cieˆncias, Brazil 67, 249–258. o, Kiadó: Academia Brasileira de Cieˆncias. * Filleul, Arnaud, John G. Maisey (2004) - Redescription of Santanichthys diasii (Otophysi, Characiformes) from the Albian of the Santana Formation and Comments on Its Implications for Otophysan Relationships”. ''American Museum Novitates'', New York, NY, USA 3455, American Museum of Natural History {{Taxonbar, from=Q839380 Prehistoric teleostei Prehistoric ray-finned fish genera Toarcian genus first appearances Bathonian genera Callovian genus extinctions Jurassic bony fish Jurassic fish of Europe Jurassic England Jurassic France Jurassic Germany Jurassic Italy Jurassic Norway Fossils of England Fossils of France Fossils of Germany Fossils of Italy Fossils of Norway Fossil taxa described in 1843 Taxa named by Louis Agassiz