''Leptolepis'' (from , 'slight' and 'scale') is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

fish that lived in what is now Europe (Germany, Luxembourg, France, England, Italy and maybe Greece) and North of Africa (Algeria, Tunisia and Morocco) during the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

period (

Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 192.9 ±0.3 Ma and 184.2 ±0.3 Ma (million years ago). The Plie ...

–

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 165.3 ± 1.1 Ma (million years ago) and 161.5 ± 1.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

ages).

Taxonomy

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 purpose of classifying organisms that do not fit anywhere else. They are typically defined by e ...

for various small, unspecialised teleosts that did not form a natural

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

. 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 buttenheimensis'' * ''Leptolepis coryphaenoides'' * ''Leptolepis curvisulcatus'' * ''Leptolepis flexuosus'' * ''Leptolepis jaegeri'' * ''Leptolepis kremmeldorfensis'' * ''Leptolepis inaequalis'' * ''Leptolepis nathorsti'' * ''Leptolepis macrocephalus'' * ''Leptolepis normandica'' * ''Leptolepis saltviciensis'' * ''Leptolepis skyensis'' * ''Leptolepis steberae'' * ''Leptolepis woodwardi''

Species formerly placed in ''Leptolepis''

* ''Leptolepis talbragarensis'' (Now referred to '' Cavenderichthys'') * ''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. The type species ''Leptolepis coryphaenoides'' is placed as a stem-group

Teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

. Cladogram of Teleosteomorpha after Sferco et al. 2021:

Appearance

Clarkeiteuthis and Leptolepis reconstruction

Length of ''Leptolepis'' was about long, and superficially resembled the unrelated modern

herring Herring are various species of forage fish, belonging to the Order (biology), order Clupeiformes. Herring often move in large Shoaling and schooling, schools around fishing banks and near the coast, found particularly in shallow, temperate wate ...

. While more basal teleosts such as ''

Pholidophorus ''Pholidophorus'' (from , 'horny scale' and , 'to bear') is an extinct genus of Stem group, stem-teleost fish. Numerous species were assigned to this genus in the past, but only the type species ''Pholidophorus latiusculus'', from the Late Tria ...

'' 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 Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

, ''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 scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

s, which lacked the covering of ganoine present in more basal teleosts. These two developments made swimming easier, as the bony

spine Spine or spinal may refer to: Science Biology * Spinal column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoology), ...

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 the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of ...

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

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

. '' 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 Pterosaur '' Dorygnathus'' preserves remains of ''Leptolepis'' in its stomach.

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'' and '' Hulettia''. 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