Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous of Australia, Europe, North America and South America. The family is more inclusive than the archetypal short-necked large headed species that are placed in the subclade Thalassophonea, with basal forms resembling other plesiosaurs with long necks. They became extinct during the early Late Cretaceous and were subsequently replaced by the mosasaurs. It was formally named by Harry G. Seeley in 1874.
Pliosauridae
The Plesiosauria or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Image: Paleo Hall at HMNS plesiosaur
Image: Peloneustes philarchus Tubingen
First published plesiosaur skeleton, 1719 (specimen NHMUK PV R.1330)
As this illustration shows, Conybeare by 1824 had gained a basically correct understanding of plesiosaur anatomy.