Plesiosauroidea

Plesiosauroids Temporal range: Late Triassic - Late Cretaceous, 210–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Life restoration of Elasmosaurus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Clade:	†Neoplesiosauria
Superfamily:	†Plesiosauroidea Gray, 1825
Subgroups
†Eoplesiosaurus †Franconiasaurus[1] †Plesiopharos †Cryptoclidia †Microcleididae †Plesiosauridae

Plesiosauroidea (/ˈpliːsiəsɔːr/; Greek: πλησιος plēsios 'near, close to' and σαυρος sauros 'lizard') is an extinct clade of carnivorous marine reptiles. They have the snake-like longest neck to body ratio of any reptile. Plesiosauroids are known from the Jurassic and Cretaceous periods. After their discovery, some plesiosauroids were said to have resembled "a snake threaded through the shell of a turtle",^[2] although they had no shell.

Plesiosauroidea appeared at the Early Jurassic Period (late Sinemurian stage) and thrived until the K-Pg extinction, at the end of the Cretaceous Period. The oldest confirmed plesiosauroid is Plesiosaurus itself, as all younger taxa were recently found to be pliosauroids.^[3] While they were Mesozoic diapsid reptiles that lived at the same time as dinosaurs, they did not belong to the latter. Gastroliths are frequently found associated with plesiosaurs.^[4]