Thalattosauroidea is a superfamily of

thalattosaur Thalattosauria (Greek for "sea lizards") is an extinct order of prehistoric marine reptiles that lived in the middle to late Triassic period. Thalattosaurs were diverse in size and shape, and are divided into two superfamilies: Askeptosauroidea an ...

s, a

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

group of marine reptiles. It was named in 1904 by paleontologist

John Campbell Merriam John Campbell Merriam (October 20, 1869 – October 30, 1945) was an American paleontologist, educator, and conservationist. The first vertebrate paleontologist on the West Coast of the United States, he is best known for his taxonomy of ver ...

to include the genus '' Thalattosaurus'' from

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

. Thalattosauroids are one of two groups of Thalattosauria, the other being Askeptosauroidea. Thalattosauroids make up the "traditional" thalattosaurs with large downturned snouts, short necks, and long, paddle-like tails.

Classification

Thalattosauria includes North American genera such as ''Thalattosaurus'' and ''

Nectosaurus ''Nectosaurus'' is a genus of thalattosaur (marine diapsid reptiles) which lived during the Late Triassic in what is now California. The type and only known species, ''Nectosaurus halius'', was found in the Hosselkus Limestone and described by ...

'' as well as recently described

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...

forms such as '' Xinpusaurus''. A 1999 study of thalattosaurs, which established much of the currently accepted

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

of the group, referred to Thalattosauroidea as Thalattosauria, while calling the larger group Thalattosauriformes. More recent phylogenetic studies have come upon the same conclusions, but refer to the group as Thalattosauroidea in order to contrast it with another superfamily of thalattosaurs, Askeptosauroidea. Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

from Wu ''et al.'' (2009) showing the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

relationships of Thalattosauroidea:

References

Triassic reptiles Triassic first appearances Triassic extinctions {{triassic-reptile-stub