Pistosauroidea is a group of marine reptiles within the superorder

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 ...

that first appeared in the latter part of the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...

and were the ancestors of plesiosaurs. Pistosauroids are rare in Triassic marine assemblages, and are represented by only a few fossils from central

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

, the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, and China. Recent phylogenetic analyses consider the Triassic pistosauroids to be a paraphyletic grouping, meaning that they do not form a true clade.

Plesiosauria The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

is now placed within Pistosauroidea, while the traditional pistosauroids are successively more basal, or primitive, sauropterygians. 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 ...

of pistosauroid relationships from Cheng ''et al.'' (2006): Below is a cladogram of pistosauroid relationships from Ketchum & Benson, 2011:

References

Sauropterygians Early Triassic first appearances Maastrichtian extinctions {{paleo-reptile-stub