page_title: Plesiosauroidea
section_title: Relationships
hierarchical_section_title: Plesiosauroidea / Evolution / Relationships
caption_attribution_description: Dolichorhynchops osborni, a plesiosaur from the Late Cretaceous of North America, pencil drawing
context_page_description: Plesiosauroidea 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", although they had no shell.
  Plesiosauroidea appeared at the Early Jurassic Period 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. 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.
context_section_description: The following cladogram follows an analysis by Benson & Druckenmiller (2014).
caption: Dolichorhynchops, a polycotylid
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