Nothosaurus ("false lizard", from the Ancient Greek nothos (νόθος), "illegitimate", and sauros (σαῦρος), "lizard") is an extinct genus of sauropterygian reptile from the Triassic period, approximately 240–210 million years ago, with fossils being distributed from North Africa and Europe to China. It is the best known member of the nothosaur order.

Quick Facts Scientific classification, Type species ...

Nothosaurus Temporal range: 240–210 Ma PreꞒ Ꞓ O S D C P T J K Pg N Middle to Late Triassic
Nothosaurus marchicus skeleton restoration in Berlin
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Nothosauroidea
Family:	†Nothosauridae
Subfamily:	†Nothosaurinae Nopcsa, 1923
Genus:	†Nothosaurus Münster, 1834
Type species
†Nothosaurus mirabilis Münster, 1834
Species
N. cristatus Hinz, Matzke & Pfretzschner, 2019 N. cymatosauroides Sanz, 1983 N. edingerae Schultze, 1970 N. giganteus Münster, 1834 N. haasi Rieppel et al., 1997 N. jagisteus Rieppel, 2001 N. luopingensis Shang et al. 2022 N. marchicus Koken, 1893 N. mirabilis Münster, 1834 (type) N. tchernovi Haas, 1980 N. yangjuanensis Jiang et al., 2006 N. zhangi Liu et al., 2014
Synonyms
Genus synonymy Conchiosaurus Meyer, 1834 Chondriosaurus Meyer, 1838 Dracosaurus Agassiz, 1846 Elmosaurus Huene, 1957 Kolposaurus Skuphos, 1893 Menodon Meyer, 1838 Oligolycus Fristch, 1894 Opeosaurus Meyer, 1847 Paranothosaurus Peyer, 1939 Shingyisaurus Young, 1965 Species synonymy Elmosaurus lelmensis Huene, 1957 Nothosaurus blezingeri Fraas, 1896 Nothosaurus schimperi Meyer, 1834 Nothosaurus angustidens Meyer, 1844 Shingyisaurus unexpectus Young, 1965 Synonyms of N. giganteus: Nothosaurus andriani Meyer, 1839 Nothosaurus angustifronis Meyer, 1844 Nothosaurus aduncidens Meyer, 1853 Nothosaurus baruthicus Geissler, 1895 Nothosaurus chelydrops Fraas, 1896 Paranothosaurus amsleri Peyer, 1939 Synonyms of N. marchicus: Conchiosaurus clavatus Meyer, 1834 Nothosaurus crassus Schroeder, 1914 Nothosaurus friedericanus Jaekel, 1911 Nothosaurus oldenburgi Schröder, 1914 Nothosaurus procerus Schröder, 1914 Nothosaurus raabi Schröder, 1914 Nothosaurus schroderi Huene, 1944 Nothosaurus venustus Münster, 1834 Nothosaurus winterswijkensis Albers and Rieppel, 2003 Synonyms of N. mirabilis: Dracosaurus bronni Giebel, 1847 Ichthyosaurus lunevillensis Alberti, 1837 Nothosaurus bergeri Meyer, 1834 Nothosaurus muensteri Meyer, 1839 Synonyms of N. yangjuanensis : Nothosaurus rostellatus Shang, 2006

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Nothosaurus was a semi-oceanic animal which probably had a lifestyle similar to that of today's seals. It was about 4 metres (13 ft), with long, webbed toes and possibly a fin on its tail.^[1] However, some species such as N. zhangi and N. giganteus were larger, up to 5–7 metres (16–23 ft).^[2] When swimming, Nothosaurus would use its tail, legs, and webbed feet to propel and steer it through the water. The skull was broad and flat, with long jaws, lined with needle teeth, it probably caught fish and other marine creatures. Trackways attributed, partly by process of elimination, to a nothosaur, that were reported from Yunnan, China in June 2014, were interpreted as the paddle impressions left as the animals dug into soft seabed with rowing motions of their paddles, churning up hidden benthic creatures that they snapped up.^[3] Once caught, few animals would be able to shake themselves free from the mouth of Nothosaurus.

In many respects its body structure resembled that of the much later plesiosaurs, but it was not as well adapted to an aquatic environment. It is thought that one branch of the nothosaurs may have evolved into pliosaurs such as Liopleurodon, a short-necked plesiosaur that grew up to 6.4 metres (21 ft), and the long-necked Cryptoclidus, a fish eater with a neck as long as 1.3 metres (4.3 ft).

There are nearly a dozen known species of Nothosaurus. The type species is N. mirabilis, named in 1834 from the Germanic Muschelkalk. Other species include N. giganteus (previously known as Paranothosaurus) from Osnabrück, Germany;^[4] N. juvenilis, also from Germany;^[5] N. edingerae from the Upper Muschelkalk and Lower Keuper;^[6] N. haasi and N. tchernovi from Makhtesh Ramon, Israel;^[7][8] N. cymatosauroides from the Spanish Muschelkalk;^[9] N. jagisteus from the Upper Muschelkalk of Hohenlohe, Germany;^[10] and N. youngi, N. yangjuanensis (and its junior synonym N. rostellatus) and the recently named N. zhangi from Guizhou, China.^{[11][12][13][14]} Several species have been described from the Lower Muschelkalk in Winterswijk, the Netherlands, including N. marchicus^[15] (and its junior synonym^[16] N. winterswijkensis^[15]) and N. winkelhorsti.^[17] Recently, the long considered lost type material of N. schimperi Meyer, 1842 from the Lower Muschelkalk of Soultz-les-Bains, Alsace, France, has been rediscovered and a lectotype has been designated.^[18]

Klein and Albers (2009) conducted a phylogenetic analysis, but did not test the monophyly of Nothosaurus, as other nothosaurids were not included in their analysis.^[17]

Several other species have been named but are now generally considered invalid. One such species, N. procerus, is now considered a junior subjective synonym of N. marchicus.^[19][20] Other species now considered junior synonyms of N. marchicus include N. crassus, N. oldenburgi, N. raabi, N. schroderi, N. venustus and the recently named N. winterswijkensis.^[16] Junior synonyms of N. giganteus, the second largest Nothosaurus species, include N. andriani, N. angustifronis, N. aduncidens, N. baruthicus and N. chelydrops.^[14]

A species level phylogenetic analysis of Nothosauridae was performed by Liu et al. (2014), and included all known valid species of the family and Nothosaurus apart from Lariosaurus stensioi (type of Micronothosaurus), Nothosaurus cymatosauroides, and Ceresiosaurus lanzi. Due to the inclusion of other nothosaurids other than Nothosaurus, the monophyly of Nothosaurus was tested for the first time. The analysis found both Lariosaurus and Nothosaurus to be polyphyletic in regard to each other and all the other genera of the family, making a systematic revision of these two genera necessary. Below, their results are shown with type species of named nothosaurid genera noted.^[14] Later, in 2017, the species N. juvenilis, N. youngi, and N. winkelhorsti were formally moved to Lariosaurus.^[21]