Thalattosauroidea is a

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

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

s, a

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

group of

marine reptile Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. Only about 100 of the 12,000 extant reptile species and subspecies are classed as marine reptiles, including mari ...

s. 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 ve ...

to include the genus ''

Thalattosaurus ''Thalattosaurus'' (pronounced: , from and ) is an extinct genus of marine reptile in the family Thalattosauroidea. Known exclusively from the Triassic period, it was a long shellfish-eating diapsid with paddle-like limbs and a down-turned ros ...

'' from

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. Thalattosauroids are one of two groups of Thalattosauria, the other being

Askeptosauroidea Askeptosauroidea is a superfamily of thalattosaurs, a Triassic group of marine reptiles. Askeptosauroidea is one of two major subgroups of Thalattosauria, the other being Thalattosauroidea. It includes the family Askeptosauridae and a more basa ...

. 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 Reptile, reptiles) which lived during the Late Triassic in what is now California. The type species, type and only known species, ''Nectosaurus halius'', was found in the Hosselkus Limest ...

'' as well as recently described

Chinese Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...

forms such as ''

Xinpusaurus ''Xinpusaurus'' is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou, China. Several species have been named since 2000: the type species ''X. suni'' along with the species ''X. bamaolinensis'' and ''X. kohi''. A 2013 ...

''. A 1999 study of thalattosaurs, which established much of the currently accepted

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

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 language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

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

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

relationships of Thalattosauroidea:

References

{{Taxonbar, from=Q3519450 Thalattosauria Triassic first appearances Triassic extinctions