Editing Plesiosauroidea (section)

{{Short description|Extinct clade of reptiles}}
{{Automatic taxobox
| name = Plesiosauroids
| fossil_range = [[Late Triassic]] - [[Late Cretaceous]], {{fossilrange|210|66}}
| image = {{multiple image|perrow = 2/1|total_width=300
| align = center
| image1 = Dolichorhynchops.jpg
| image2 = Paleo Hall at HMNS plesiosaur.jpg
| image3 = Traskasaura (mounted skeleton, Canadian Museum of Nature).jpg
| footer = Three plesiosauroids (clockwise from top left):  ''[[Dolichorhynchops]]'', ''[[Plesiosaurus]]'', ''[[Traskasaura]]''
| border = infobox}}
| taxon = Plesiosauroidea
| authority = [[John Edward Gray|Gray]], 1825
| subdivision_ranks = Subgroups
| subdivision = 
* {{extinct}}''[[Eoplesiosaurus]]''
* {{extinct}}''[[Franconiasaurus]]''
* {{extinct}}''[[Plesiopharos]]''
* {{extinct}}''[[Plesiopterys]]''
* {{extinct}}'''[[Microcleididae]]'''
* {{extinct}}'''[[Plesiosauridae]]'''
* {{extinct}}'''Cryptoclidia''' <small>Ketchum and Benson, 2010</small>
** {{extinct}}'''[[Cryptoclididae]]'''
** {{extinct}}'''Xenopsaria''' <small>C. V. Miller ''et al.'', 2020</small>
*** {{extinct}}'''[[Elasmosauridae]]'''
*** {{extinct}}'''Leptocleidia''' <small>Ketchum and Benson, 2010</small>
**** {{extinct}}'''[[Leptocleididae]]'''
**** {{extinct}}'''[[Polycotylidae]]'''
}}

'''Plesiosauroidea''' ({{IPAc-en|ˈ|p|l|iː|s|i|ə|s|ɔər}}; [[Ancient Greek|Greek]]: {{lang|grc|πλησιος}} {{Transliteration|grc|plēsios}} 'near, close to' and {{lang|grc|σαυρος}} {{Transliteration|grc|sauros}} 'lizard') is an [[extinct]] [[clade]] of [[carnivore|carnivorous]] [[Marine (ocean)|marine]] [[Reptilia|reptiles]]. They have the [[snake]]-like longest neck to body ratio of any reptile. '''Plesiosauroids''' are known from the [[Jurassic]] and [[Cretaceous]] [[Period (geology)|periods]]. After their discovery, some plesiosauroids were said to have resembled "a snake threaded through the shell of a turtle",<ref name=":0">{{Cite web |last=Everhart |first=Mike |date=2005-10-14 |title=A Snake Drawn Through the Shell of a Turtle |url=http://www.oceansofkansas.com/Snaketurtle.html |access-date=2010-06-10 |work=[[Oceans of Kansas Paleontology]]}}</ref> although they had no shell.

Plesiosauroidea appeared at the [[Early Jurassic]] [[Period (geology)|Period]] (late [[Sinemurian]] stage) and thrived until the [[Cretaceous–Paleogene extinction event|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 [[pliosauroid]]s.<ref name=Marmornectes>{{cite journal |author1=Ketchum, Hilary F. |author2=Benson, Roger B. J. |year=2011 |title=A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids |journal=Special Papers in Palaeontology |volume=86 |pages=109–129 |url=https://www.palass.org/publications/special-papers-palaeontology/archive/86/article_pp109-129}}</ref> While they were [[Mesozoic]] [[Diapsida|diapsid]] reptiles that lived at the same time as dinosaurs, they did not belong to the latter. [[Gastrolith]]s are frequently found associated with plesiosaurs.<ref name="cedaro-gast-occ-168" />