Lepidotes

Lepidotes
Temporal range: Early Jurassic (Toarcian)
Fossil specimen of L. gigas
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Clade: Ginglymodi
Order: Lepisosteiformes
Family: †Lepidotidae
Genus: †Lepidotes
Agassiz, 1832
Type species
†Lepidotes gigas
Agassiz, 1832
Species
  • †L. elvensis (Blainville, 1818) (orig. Cyprinus)
  • †L. gigas (type) Agassiz, 1832
  • †L. semiserratus Agassiz, 1836
Synonyms
Genus synonymy
  • Lepidosaurus Meyer, 1833
  • Serobodus Münster, 1812
  • Sphaerodus Agassiz, 1833
  • Plesiodus Wagner, 1863
  • Prolepidotus Zeitschr, 1983
Species synonymy
  • L. elvensis
  • Cyprinus elvensis de Blainville, 1818
  • Lepidotes gigas Agassiz, 1832
  • Lepidotus gigas (Agassiz, 1832) Agassiz, 1833
  • Lepidotus elcensis Quenstedt, 1847 (lapsus calami)
  • L. semiserratus
  • Lepidotus latissimus Agassiz, 1833
  • Lepidotus umbonatus Agassiz, 1833
  • L. gallineki
  • Prolepidotus gallineki (Michael, 1863) Michael, 1893
  • L. tuberculatus
  • Lepidotus unguiculatus Agassiz, 1837
  • Shaerodus minor Agassiz, 1844
  • Pycnodus rudis Phillips, 1871

Lepidotes (from Greek: λεπιδωτός lepidōtós, 'covered with scales') (previously known as Lepidotus) is an extinct genus of marine ray-finned fish known from the Early Jurassic (Toarcian) of Europe. It belongs to Ginglymodi, a clade of fish whose only living representatives are the gars (Lepisosteidae). The type species L. gigas and close relatives are thought to be members of the family Lepidotidae, part of the order Lepisosteiformes within Ginglymodi, with other species occupying various other positions within Ginglymodi. It was one of the earliest known close relatives of modern gars and is classified in the same order as them, although morphologically it still superficially resembled the earlier-diverging semionotiform fishes.

Taxonomy

Lepidotes has long been considered a wastebasket taxon, characterised by "general features, such as thick rhomboid scales and, for most of the species, by semi-tritorial or strongly tritoral (broad, flat teeth adapted for crushing) dentition" with dozens of species previously assigned to it. Fossils attributed to Lepidotes were originally found in Jurassic and Cretaceous rocks worldwide. However, more recently it has been argued that Lepidotes should be restricted to species closely related to the type species L. gigas, which are only known from the Early Jurassic of Western and Central Europe, with most other species being not closely related, with other species transferred to new genera such as Scheenstia.

The closest relative of Lepidotes sensu stricto was Mengius, a similar fish from the Toarcian of Germany.

Species

The following valid species are known:

L. gigas

The type species of the genus, it is known from the Early Jurassic (Toarcian) of Germany, where it is known from the Posidonia Shale lagerstätte. Based on some specimens, it could measure up to 75 centimetres (2.46 ft) long. In the past, it has been confused with L. elvensis from France, which was described earlier but not under the genus Lepidotes, and has thus previously been treated as a junior synonym. However, more recently the two species have been found to differ in skull shape and morphology, and are thus now understood as distinct species.

L. elvensis

Fossil of L. elvensis

L. elvensis was described by Ducrotay de Blainville in 1818, originally as a species of Cyprinus. The type specimen is known from an undifferentiated Toarcian-aged deposit in La Caine, France, and is housed in the Paris Museum of Natural History. The external bones of this species are smooth, but some have sparsely placed coarse tuberculations (protuberances). The frontal bone is more than twice the length of the parietal in the specimens. It also has a comparatively narrow marginal symphysis (articulation).

L. semiserratus

Fossil specimen of L. semiserratus

This species was named by Agassiz in 1837 and is known from some incomplete remains. It has been classified as closely related to L. elvensis. It is more elongate than L. elvensis, being four times as long as tall. It also has more sharply angulated sutures between its parietals, and the parietals are also proportionally longer. It is known from the Upper Lias of Yorkshire, England, where they are known from the Toarcian-aged Whitby Mudstone Formation.

Another species definitively assignable to Lepidotes, "L." buelowianus from the Toarcian-aged Grimmen Formation of Germany, has been identified more recently as a nomen dubium, due to the type specimen being lost and the original description being improperly done.

Reassigned species

Various fish from the Late Jurassic to mid-Cretaceous previously assigned into Lepidotes have now been moved into their own genera, including Scheenstia, Callipurbeckia, Isanichthys, Thaiichthys, Quasimodichthys, Hoyasotes, Lepidhoyas and Adrianaichthys. Some of these such as Callipurbeckia are placed in the earlier-diverging order Semionotiformes, while others are retained in the Lepisosteiformes.

The following species have not yet been reclassified into a different genus, but are not considered true members of Lepidotes:

Description

Inhabiting shallow seas, Lepidotes was typically about 30 centimetres (12 in) long. The body was covered with thick, enamelled scales.

Lepidotes was one of the earliest fish in which the upper jawbones were no longer attached to the jugal bone. This allowed the jaws to be stretched into a 'tube' so that the fish could suck in prey from a greater distance than in previous species. This system is still seen in some modern fish, such as carp.

Specimen of L. elvensis

Also on the jaws of Lepidotes were prominent foramina on the maxilla, suggesting significant innervation within the jaws. This suggests a thickened upper lip or potentially barbels, which may have supported sensory organs.

Lepidotes scales are ovular in shape, and are 18.5 millimetres (0.73 in) long and 3 millimetres (0.12 in) thick at the thickest point. The scales are smooth and shiny on the external surface, with only a few small depressions scattered toward the centre that are shaped like punctures.

Stomach contents of Lepidotes from the Early Jurassic of Germany have found remains of crustacean cuticles, and it is suggested that they fed on relatively soft-bodied prey, which was grasped with the slender marginal teeth, before being crushed by the rounded palatal teeth.

Distinguishing characteristics

Many characteristics were identified by Woodward in 1895, and they are listed below:

  • a fusiform trunk only moderately compressed;
  • the fact that the marginal teeth are compressed;
  • the presence of stouter inner teeth that are smooth;
  • ossified ribs;
  • very large fin-fulera on all fins;
  • that all paired fins are small;
  • short and deep dorsal and anal fins;
  • very robust, smooth or feebly oriented scales;
  • flank scales that are not much deeper than wide;
  • scales ventrally nearly as deep as broad;
  • and the presence of inconspicuous dorsal and ventral ridge-scales.

References

  1. ↑ Agassiz, L. (1832), Untersuchungen über die fossilen Fische der Lias-Formation. Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde 3: 145
  2. ↑ López-Arbarello, A. (2012). "Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)." PLoS One, 7(7): e39370. doi:10.1371/journal.pone.0039370
  3. 1 2 3 4 5 Woodward, A.S. (1895). "Catalogue of the Fossil Fishes in the British Museum (Natural History)". 2. British Museum of Natural History Department of Geology: 77–119. doi:10.5962/bhl.title.61854. hdl:2027/coo1.ark:/13960/t3jx39x2t. {{cite journal}}: Cite journal requires |journal= (help)
  4. ↑ Hunterian Museum Geology Collections. "Lepidotes" Archived 2017-03-12 at the Wayback Machine.
  5. 1 2 3 4 5 6 7 8 López-Arbarello, Adriana (2012-07-11). Steinke, Dirk (ed.). "Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)". PLOS ONE. 7 (7) e39370. Bibcode:2012PLoSO...739370L. doi:10.1371/journal.pone.0039370. ISSN 1932-6203. PMC 3394768. PMID 22808031.
  6. ↑ Cavin, Lionel; Deesri, Uthumporn; Olive, Sébastien (2020-03-18). "Scheenstia bernissartensis (Actinopterygii: Ginglymodi) from the Early Cretaceous of Bernissart, Belgium, with an appraisal of ginglymodian evolutionary history". Journal of Systematic Palaeontology. 18 (6): 513–527. Bibcode:2020JSPal..18..513C. doi:10.1080/14772019.2019.1634649. ISSN 1477-2019. S2CID 199631685.
  7. ↑ John G. Maisey, Discovering Fossil Fishes, 1996:150, 152.
  8. ↑ Bonde, N.; Cristiansen, P. (2003). "New dinosaurs from Denmark". Comptes Rendus Palevol. 2. 2 (13): 13–26. Bibcode:2003CRPal...2...13B. doi:10.1016/S1631-0683(03)00009-5.
  9. ↑ Clemmensen, Lars B.; Milàn, Jesper; Adolfssen, Jan Schulz; Estrup, Eliza Jarl; Frobøse, Nicolai; Klein, Nicole; Mateus, Octávio; Wings, Oliver (2015-12-16). "The vertebrate-bearing Late Triassic Fleming Fjord Formation of central East Greenland revisited: stratigraphy, palaeoclimate and new palaeontological data". Geological Society, London, Special Publications. 434 (1): 31–47. doi:10.1144/sp434.3. ISSN 0305-8719. S2CID 130069487.
  10. ↑ Thies, Detlev; Stevens, Kevin; Ansorge, Jörg (2026-06-01). "A new lepisosteiform neopterygian (Actinopterygii) from the lower Toarcian Grimmen Formation (Lower Jurassic) of Mecklenburg and Western Pomerania, Germany". PalZ. 100 (2): 343–369. doi:10.1007/s12542-023-00683-5. ISSN 1867-6812.
  11. 1 2 López-Arbarello, Adriana (2012). "Phylogenetic interrelationships of ginglymodian fishes (Actinopterygii: Neopterygii)". PLOS ONE. 7 (7) e39370. Bibcode:2012PLoSO...739370L. doi:10.1371/journal.pone.0039370. ISSN 1932-6203. PMC 3394768. PMID 22808031.
  12. ↑ Cavin, Lionel; Deesri, Uthumporn; Suteethorn, Varavudh (January 2013). "Osteology and relationships of Thaiichthys nov. gen.: a Ginglymodi from the Late Jurassic - Early Cretaceous of Thailand: GINGLYMODI FROM THE MESOZOIC OF THAILAND". Palaeontology. 56 (1): 183–208. doi:10.1111/j.1475-4983.2012.01184.x.
  13. ↑ Cavin, Lionel; Deesri, Uthumporn; Suteethorn, Varavudh (2013). "Osteology and relationships of Thaiichthys nov. gen.: a Ginglymodi from the Late Jurassic – Early Cretaceous of Thailand". Palaeontology. 56 (1): 183–208. doi:10.1111/j.1475-4983.2012.01184.x. ISSN 1475-4983.
  14. ↑ François J. Meunier; René-Paul Eustache; Didier Dutheil; Lionel Cavin (2016). "Histology of ganoid scales from the early Late Cretaceous of the Kem Kem beds, SE Morocco: systematic and evolutionary implications". Cybium. 40 (2): 121–132. doi:10.26028/cybium/2016-402-003.
  15. ↑ Paiva, Hanna Carolina Lins de; Gallo, Valéria (2018-12-01). "Quasimodichthys gen. nov. (Neopterygii: Semionotiformes): A morphological and ontogenetic study". Journal of South American Earth Sciences. 88: 132–143. doi:10.1016/j.jsames.2018.08.010. ISSN 0895-9811.
  16. ↑ Paiva, Hanna Carolina Lins de (2017). Revisão de Lepidotes piauhyensis Roxo e Löfgren, 1936 (Neopterygii, Semionotiformes) e considerações sobre as espécies brasileiras do gênero Lepidotes (MS thesis). Universidade do Estado do Rio de Janeiro. Retrieved 2026-10-09.
  17. ↑ Thies, Detlev (1989-03-30). "Lepidotes gloriae, sp. nov. (Actinopterygii: Semionotiformes) from the Late Jurassic of Cuba". Journal of Vertebrate Paleontology. 9 (1). Taylor & Francis: 18–40. doi:10.1080/02724634.1989.10011736. ISSN 0272-4634.
  18. ↑ Jain, Sohan L. (1983-12-01). "A review of the genus Lepidotes (Actinopterygii : Semionotiformes), with special reference to the species form Kota Formation (Lower Jurassic), India". Journal of the Palaeontological Society of India. 28 (1). SAGE Publications: 7–42. doi:10.1177/0971102319830102. ISSN 0552-9360.
  19. ↑ Brito, Paulo M.; Gallo, Valéria (2003-04-11). "A new species of Lepidotes (Neopterygii: Semionotiformes: Semionotidae) from the Santana Formation, Lower Cretaceous of northeastern Brazil". Journal of Vertebrate Paleontology. 23 (1). Taylor & Francis: 47–53. doi:10.1671/0272-4634(2003)23[47:ANSOLN]2.0.CO;2. ISSN 0272-4634.
  20. 1 2 Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 37. ISBN 1-84028-152-9.
  21. ↑ Thies, Detlev (2023-09-03). "Comments on the cranial and pectoral girdle osteology of Lepidotes gigas (Actinopterygii, Lepisosteiformes) from the Lower Jurassic (lower Toarcian) of Germany". Journal of Vertebrate Paleontology. 43 (5). Taylor & Francis: e2330586. doi:10.1080/02724634.2024.2330586. ISSN 0272-4634.{{cite journal}}: CS1 maint: article number as page number (link)
  22. 1 2 Lambe, L.M. (1902). "New Genera and Species from the Belly River Series (mid cretaceous)". Geological Survey of Canada. Contributions to Canadian Palaeontology. 3: 25–81.
  23. ↑ Thies, Detlev; Stevens, Kevin; Stumpf, Sebastian (2021-06-03). "Stomach contents of the Early Jurassic fish † Lepidotes Agassiz, 1832 (Actinopterygii, Lepisosteiformes) and their palaeoecological implications". Historical Biology. 33 (6): 868–879. Bibcode:2021HBio...33..868T. doi:10.1080/08912963.2019.1665040. ISSN 0891-2963. S2CID 203892069.