Classification

Plesiosaurian clades

This nested classification for Plesiosauria shows the major clades (groups). Note that some cladistic analyses have placed the Rhomaleosauridae outside of Pliosauroidea (=pliosaurs), in a sister relationship with a clade called Neoplesiosauria (Plesiosauroidea + Pliosauridae) (e.g. Benson et al. 2012). However, this clade does not resolve in other analyses, so I have used a traditional approach here and nested Rhomaleosauridae within pliosauroids.

Sauropterygian clades

Plesiosaurs (=Plesiosauria) are derived sauropterygians. This nested classification of Sauropterygia shows the position of Plesiosauria relative to other major sauropterygian clades.

Redundant sauropterygian clades

‘Nothosauriformes’

‘Cimoliasauridae’