Editing Plesiosaurus (section)

==Palaeoenvironment==
[[File:Plesiosaurus sp.jpg|thumb|left|Tentatively referred specimen in [[Calgary]]]] 
Unequivocal specimens of ''Plesiosaurus dolichodeirus'' are limited to the Lyme Regis area of Dorset.<ref>Storrs 1997 pp. 148</ref> It appears to be the most common species of plesiosaur in the Lias Group of England.<ref>Storrs 1997 pp. 179</ref> ''Plesiosaurus'' is best represented from the "upper part of the [[Blue Lias]], the 'Shales with Beef,' and the lower Black Ven Marls" the latter of which form part of the [[Charmouth Mudstone]]; using the Lias Group [[ammonite]] fossil zones, these rocks date to the early [[Sinemurian]] stage. Some other ''Plesiosaurus'' fossils are from later Sinemurian rocks. The oldest specimen may be a skull thought to come from late [[Rhaetian]] or early [[Hettangian]] rocks.<ref name=Storrs180>Storrs 1997 pp.180</ref>