Leptonectes

Leptonectes
Leptonectes tenuirostris in London's Natural History Museum
Temporal occurrence
Upper Triassic - Lower Jurassic ( Rhaetian - Pliensbachian )
208.5 to 182.7 million years
Locations
Europe ( Germany , England , Switzerland , Belgium )
Systematics
Land vertebrates (Tetrapoda) Sauropsida Diapsida Ichthyosaur (Ichthyosauria) Leptonectidae Leptonectes
Scientific name
Leptonectes
McGowan , 1996
species
L. moorei (McGowan and Milner, 1990) L. solei (McGowan, 1993) L. tenuirostris (Conybeare, 1822) ( type species )

Leptonectes ( Greek. For "leaner swimmers" from λεπτός Leptos "slim" and νηκτής nektes "float") is a genus of ichthyosaur , a group of extinct marine reptiles, from the Upper Triassic ( Rhaetian ) and the Lower Jurassic ( Pliensbachian ) from Europe ( England , Germany , Belgium & Switzerland ).

features

Leptonectes is a genus of medium-sized ichthyosaurs with a length of - depending on the species - 3 to 5 meters. The skull of Leptonectes is long and very narrow, but without a pronounced overbite as in Eurhinosaurus or Excalibosaurus . The eye socket is greatly enlarged and mostly aligned to the side. The rear fin measures less than two-thirds of the front fin. Further features are the small supratemporal windows and the smooth surface of the teeth. The caudal fin was less developed than other ichthyosaurs and went down slightly.

Systematics and taxonomy

The Leptonectidae are closely related to the Temnodontidae and the Suevoleviathanidae . Within the Leptonectidae there is a noticeable increase in overbite. While in Leptonectes there is only a minimal difference in the ratio between the upper and lower jaw, this is clearly pronounced in Excalibosaurus and extreme in Eurhinosaurus . The following cladogram shows the relationships within the Leptonectidae and their sister groups .

Parvipelvia	Macgowania      Hudsonelpidia   Neoichthyosauria    Temnodontosaurus   Leptonectidae    Leptonectes       Excalibosaurus      Eurhinosaurus      Suevoleviathan      Thunnosauria

Geographical distribution

Leptonectes tenuirostris from Lyme Regis , England

Many specimens of the genus Leptonectes come from the south of England. Street ( Somerset ), Lyme Regis , Charmouth and Seatown ( Dorset ) are some of the most important sites. In Germany, this ichthyosaur was found in Dusslingen . Further finds were made in southern Belgium. Leptonectes has now also been detected in Switzerland from Unterer Hauenstein ( Canton Solothurn ).

Fossil record

Leptonectes occurs for the first time in the preplanorbis layers of the Rhaetium ( Upper Triassic ) of southern England . The last evidence comes from the upper Pliensbachian in Switzerland.

Selection of museums with copies

Great Britain

• Natural History Museum in London

Switzerland

• Naturmuseum Olten , Canton Solothurn

Canada

• Royal Ontario Museum , Toronto

Japan

• National Museum of Natural Sciences , Tokyo

Sources and References

literature

• Christopher McGowan, Ryosuke Motani: Ichthyopterygia , Handbook of Paleoherpetology, Part 8, Verlag Dr. Friedrich Pfeil, 2003.

Web links

Commons : Leptonectes  - collection of images, videos and audio files

• https://paleobiodb.org/cgi-bin/bridge.pl?a=checkTaxonInfo&taxon_no=95785&is_real_user=0

Individual evidence

1. ↑ ^{a b c} M. W. Maisch: Phylogeny, systematics, and origin of the Ichthyosauria - the state of the art. In: Palaeodiversity 3, 2010, pp. 151-214.
2. ^ MW Maisch, AT Matzke: The Ichthyosauria. In: Stuttgart contributions to natural history series B (geology and palaeontology) 298, 2000, pp. 1–159.
3. ↑ Cristopher McGowan: Dinosaurs, Spitfires, & Sea Dragons. Harvard University Press, Cambridge, Massachusetts; London, England, 1992, ISBN 0-674-20770-X , p. 365.
4. ^ C. McGowan: A putative ancestor for the swordfish-like ichthyosaur Eurhinosaurus. In: Nature 322, No. 6078, 1986, pp. 723-742.
5. ^ RD Marek, BC Moon, M. Williams, MJ Benton: The skull and endocranium of a Lower Jurassic Ichthyosaur based on digital reconstructions. In: Palaeontology 58, 2015, pp. 454–456.
6. ↑ MW Maisch: New specimens of the rare ichthyosaur genus Suevoleviathan MAISCH 1998 from the lower Jura of southwest Germany. In: Geologica et Paleontologica 35, 2001, pp. 145-160.
7. ↑ ^{a b} M. W. Maisch, AG Reisdorf: Evidence for the longest stratigraphic range of a post-Triassic Ichthyosaur: a Leptonectes tenuirostris from the Pliensbachian (Lower Jurassic) of Switzerland. In: Geobios 39, 2006, pp. 491-505.
8. ^ C. McGowan: A revision of the Longipinnate Ichthyosaurs of the Lower Jurassic of England, with descriptions of two new species (Reptilia: Ichthyosauria). In: Life Science Contribution 97, 1974, pp. 1-37.
9. ↑ Archived copy ( memento of the original from April 14, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (accessed on August 6, 2015) 
10. ↑ http://a-fragi.blogspot.de/2011/01/leptonectes-tenuirostris.html (accessed on August 6, 2015)