| Nothosauroidea | |
|---|---|
 | |
| Nothosaurus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Clade: | †Eosauropterygia |
| Order: | †Nothosauroidea Baur, 1889 |
| Subgroups | |
Nothosaurs (superfamilyNothosauroidea) wereTriassic marinesauropterygianreptiles. They averaged about 3 metres (10 ft) in length, with a long body and tail.[1] The feet were paddle-like, and are known to have been webbed in life, to help power the animal when swimming.[2] 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 offish andsquid.
The Nothosauroidea has been suggested to consist of two suborders, thePachypleurosauria, which are small primitive forms, and the Nothosauria (including two familiesNothosauridae andSimosauridae), which may have evolved from pachypleurosaurs.
The relation of pachypleurosaurs to Nothosauroidea is uncertain, as several analyses recover the clade asbasal toEusauropterygia, e.i. theclade formed by Nothosauria and Pistosauroidea, instead as thesister taxon of Nothosauria.[3] Many recent analyses have recovered the pachypleurosaurs as a basal clade ofeosauropterygians outside of the nothosauroidea.[4][5]
Nothosaur-like reptiles were in turn ancestral to the more completely marineplesiosaurs, which replaced them at the end of the Triassic period.
In their 2024 description ofDianmeisaurus mutaensis, Hu, Li & Liu recovered the Nothosauroidea as thesister taxon to thePachypleurosauria. The results of theirphylogenetic analyses are shown in thecladogram below:[5]
A 2024 description of a fossil nothosaur vertebra from theAnisian ofNew Zealand indicates that nothosaurs dispersed worldwide from their region of origin in the northernTethys much earlier than presumed, eventually reaching the southern polar region ofPanthalassa by theMiddle Triassic. This vertebra is the oldestsauropterygian fossil from theSouthern Hemisphere, and appears to be from a taxon related toNothosaurus andLariosaurus.[6]
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