Editing Plesiosauroidea (section)

===Relationships===
[[Image:Muraenosaurus BW.jpg|right|thumb|''[[Muraenosaurus]]'', a cryptoclidid]]
[[Image:Styxosaurus BW.jpg|right|thumb|''[[Styxosaurus]]'', an elasmosaurid]]
[[File:Trinacromerum_BW.jpg|thumb|''[[Trinacromerum]]'', a polycotylid]]
Within Plesiosauroidea, there is a more exclusive group, '''Cryptoclidia'''.  Cryptoclidia was named and defined as a node clade in 2010 by [[Hilary Ketchum]] and [[Roger Benson]]: the group consisting of the [[last common ancestor]] of ''[[Cryptoclidus]] eurymerus'' and ''[[Polycotylus]] latipinnis''; and all its descendants.<ref name=KB10>{{cite journal |last=Ketchum |first=H.F. |author2=Benson, R.B.J. |year=2010 |title=Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylogenetic analyses |journal=Biological Reviews |volume=85 |issue=2 |pages=361–392 |doi=10.1111/j.1469-185X.2009.00107.x |pmid=20002391|s2cid=12193439 }}</ref>

The smaller group within Cryptoclidia was erected prior, in 2007 under the name "Leptocleidoidea".<ref name=DR08>{{cite journal |last=Druckenmiller |first=P.S. |author2=Russel, A.P. |year=2007 |title=A phylogeny of Plesiosauria (Sauropterygia) and its bearing on the systematic status of ''Leptocleidus'' Andrews, 1922 |url=http://www.bio.ucalgary.ca/contact/faculty/pdf/russell/321.pdf |journal=Zootaxa |volume=1863 |pages=1–120 |doi=10.11646/zootaxa.1863.1.1 |isbn=978-1-86977-262-8 |issn=1175-5334 |url-status=dead |archive-url=https://web.archive.org/web/20111004103333/http://www.bio.ucalgary.ca/contact/faculty/pdf/russell/321.pdf |archive-date=2011-10-04 }}</ref> Although established as a clade, the name Leptocleidoidea implies that it is a [[superfamily (biology)|superfamily]]. Leptocleidoidea is placed within the superfamily Plesiosauroidea, so it was renamed '''Leptocleidia''' by Hilary F. Ketchum and Roger B. J. Benson (2010) to avoid confusion with ranks. Leptocleidia is a [[node-based taxon]] which was defined by Ketchum and Benson as "''[[Leptocleidus superstes]]'', ''[[Polycotylus latipinnis]]'', their most recent common ancestor and all of its descendants".<ref name=KB10/>
The following [[cladogram]] follows an analysis by Benson & Druckenmiller (2014).<ref name=plesiosaurturnover>{{Cite journal | last1 = Benson | first1 = R. B. J. | last2 = Druckenmiller | first2 = P. S. | doi = 10.1111/brv.12038 | title = Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition | journal = Biological Reviews | pages =  1–23| year = 2013 | pmid =  23581455| volume=89| issue = 1 | s2cid = 19710180 }}</ref>
{{clade| style=font-size:100%;line-height:100%
      |label1='''Plesiosauroidea'''
      |1={{clade
               |1=''[[Plesiosaurus]]''
               |2={{clade
               |1=''[[Eretmosaurus]]''
               |2=''[[Westphaliasaurus]]''
               |3=[[Microcleididae]]
               |4={{clade
                 |1=''[[Plesiopterys]]''
                 |label2=Cryptoclidia
                 |2={{clade
                  |1=[[Cryptoclididae]]
                  |label2=Xenopsaria
                  |2={{clade
                     |1=[[Elasmosauridae]]
                     |label2=Leptocleidia
                     |2={{clade
                       |1=[[Leptocleididae]]
                       |2=[[Polycotylidae]] 
}} }} }} }} }} }} }}