Nothosaurs (order Nothosauroidea) were

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

marine

sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...

s that may have lived like seals of today, catching food in water but coming ashore on rocks and beaches. They averaged about in length, with a long body and tail.F. v. Huene. 1956. Paläontologie und Phylogenie der Niederen Tetrapoden aleontology and Phylogeny of the Lower Tetrapods ''VEB Gustav Fischer Verlang, Jena'' 1-716 The feet were paddle-like, and are known to have been webbed in life, to help power the animal when swimming. The neck was quite long, and the head was elongated and flattened, and relatively small in relation to the body. The margins of the long jaws were equipped with numerous sharp outward-pointing teeth, indicating a diet of

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of liv ...

and

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting ...

Taxonomy

The Nothosauroidea consist of two suborders: * Pachypleurosauria, small primitive forms, and * Nothosauria (including two families Nothosauridae and Simosauridae), which evolved from pachypleurosaurs. The placement of pachypleurosaurs within Nothosauroidea is uncertain, as several analyses recover it as basal to Eusauropterygia, e.i. the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

formed by Nothosauria and Pistosauroidea, instead as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

of Nothosauria. However, most analyses still reinforce the traditional hypothesis of the sister taxon relationship between Pachypleurosauria and Nothosauria. Nothosaur-like reptiles were in turn ancestral to the more completely marine

plesiosaur The Plesiosauria (; Ancient Greek, Greek: πλησίος, ''plesios'', meaning "near to" and Sauria, ''sauros'', meaning "lizard") or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauro ...

s, which replaced them at the end of the Triassic period. image:Lariosaurus BW.jpg, '' Lariosaurus''. image:Keichousaurus BW.jpg, ''

Keichousaurus ''Keichousaurus'' (key-cho-saurus) is a genus of marine reptile in the pachypleurosaur family which went extinct at the close of the Triassic in the Triassic-Jurassic extinction event. The name derives from Kweichow (now Guizhou Province) in ...

''. image:Ceresiosaurus12.jpg, ''

Ceresiosaurus ''Ceresiosaurus'' is an extinct aquatic genus of lariosaurine nothosaurid sauropterygian known from the Middle Triassic (Anisian-Ladinian boundary) of Monte San Giorgio, southern Switzerland and northern Italy. Ceresiosaurus, meaning "Lizard of ...

''.

References

Sources

* * Benton, M. J. (2004), ''Vertebrate Paleontology'', 3rd ed. Blackwell Science Ltdbr>classification
* Colbert, E. H., (1969), ''Evolution of the Vertebrates'',

John Wiley & Sons Inc John Wiley & Sons, Inc., commonly known as Wiley (), is an American multinational publishing company founded in 1807 that focuses on academic publishing and instructional materials. The company produces books, journals, and encyclopedias, in ...

(2nd ed.) * Rieppel, O., (2000), Sauropterygia I, placodontia, pachypleurosauria, nothosauroidea, pistosauroidea: In: ''Handbuch der Palaoherpetologie'', part 12A, 134pp. Verlag Dr. Friedrich Pfeilbr>Table of contents
Triassic sauropterygians Taxa named by Georg Baur {{paleo-reptile-stub