Editing Plesiosauroidea

{{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" />

==History of discovery==
[[File:Mary Anning Plesiosaurus.jpg|left|thumb|Autograph letter concerning the discovery of ''Plesiosaurus dolichodeirus'' (NHMUK PV OR 22656), from Mary Anning.]]
The first complete plesiosauroid skeletons were found in England by [[Mary Anning]], in the early 19th century, and were amongst the first fossil vertebrates to be described by science. Plesiosauroid remains were found by the Scottish geologist [[Hugh Miller]] in 1844 in the rocks of the [[Great Estuarine Group]] (then known as 'Series') of western Scotland.<ref>{{Cite book |title=The Geology of Scotland |publisher=[[The Geological Society of London]] |year=2002 |editor-last=Trewin |editor-first=N. H. |location= |pages=339}}</ref> Many others have been found, some of them virtually complete, and new discoveries are made frequently. One of the finest specimens was found in 2002 on the coast of [[Somerset]] (England) by someone fishing from the shore. This specimen, called the Collard specimen after its finder, was on display in [[Taunton Museum]] in 2007. Another, less complete, skeleton was also found in 2002, in the cliffs at [[Filey]], Yorkshire, England, by an amateur palaeontologist. The preserved skeleton is displayed at [[Rotunda Museum]] in Scarborough.

==Description==
Plesiosauroids had a broad body and a short [[tail]]. They retained their ancestral two pairs of limbs, which evolved into large [[Flipper (anatomy)|flippers]].

It has been determined by teeth records that several sea-dwelling reptiles, including plesiosauroids, had a warm-blooded metabolism similar to that of mammals. They could generate [[endothermic]] heat to survive in colder habitats.<ref>{{cite journal|url=https://www.sciencedaily.com/releases/2010/06/100614093341.htm |title=Warm-blooded marine reptiles at the time of the dinosaurs |journal=Science |volume=328 |issue=5984 |pages=1379–1382 |doi=10.1126/science.1187443 |pmid=20538946 |publisher=Sciencedaily.com |date=2010-06-15 |access-date=2011-08-15|bibcode=2010Sci...328.1379B |last1=Bernard |first1=A. |last2=Lecuyer |first2=C. |last3=Vincent |first3=P. |last4=Amiot |first4=R. |last5=Bardet |first5=N. |last6=Buffetaut |first6=E. |last7=Cuny |first7=G. |last8=Fourel |first8=F. |last9=Martineau |first9=F. |last10=Mazin |first10=J.-M. |last11=Prieur |first11=A. |s2cid=206525584 |url-access=subscription }}</ref>

==Evolution==
Plesiosauroids evolved from earlier, similar forms such as [[Pistosaurus|pistosaurs]]. There are a number of [[Family (biology)|families]] of plesiosauroids, which retain the same general appearance and are distinguished by various specific details. These include the [[Plesiosauridae]], unspecialized types which are limited to the [[Early Jurassic]] period;  [[Cryptoclididae]], (e.g. ''[[Cryptoclidus]]''), with a medium-long neck and somewhat stocky build; [[Elasmosauridae]], with very long, flexible necks and tiny heads; and the [[Cimoliasauridae]], a poorly known group of small Cretaceous forms. According to traditional classifications, all plesiosauroids have a small head and long neck but, in recent classifications, one short-necked and large-headed Cretaceous group, the [[Polycotylidae]], are included under the Plesiosauroidea, rather than under the traditional Pliosauroidea. Size of different plesiosaurs varied significantly, with an estimated length of ''[[Trinacromerum]]'' being three meters and ''[[Mauisaurus]]'' growing to twenty meters.

===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]] 
}} }} }} }} }} }} }}

==Behavior==
[[Image:Plesiosaurus 3DB.jpg|thumb|left|Restoration of a ''Plesiosaurus dolichodeirus'' pair, one catching a fish.]]
Unlike their pliosauroid cousins, plesiosauroids (with the exception of the Polycotylidae) were probably slow swimmers.<ref>{{cite journal | last1 = Massare | first1 = J. A. | year = 1988 | title = Swimming capabilities of Mesozoic marine reptiles: Implications for method of predation | journal = Paleobiology | volume = 14 | issue = 2| pages = 187–205 | doi=10.1017/s009483730001191x| bibcode = 1988Pbio...14..187M | s2cid = 85810360 }}</ref> It is likely that they cruised slowly below the surface of the water, using their long flexible neck to move their head into position to snap up unwary fish or [[cephalopods]]. Their four-flippered swimming adaptation may have given them exceptional maneuverability, so that they could swiftly rotate their bodies as an aid to catching prey.

Contrary to many reconstructions of plesiosauroids, it would have been impossible for them to lift their head and long neck above the surface, in the "[[swan]]-like" pose that is often shown.<ref name=":0" /><ref>{{cite journal | last1 = Henderson | first1 = D. M. | year = 2006 | title = Floating point: a computational study of buoyancy, equilibrium, and gastroliths in plesiosaurs | journal = Lethaia | volume = 39 | issue = 3| pages = 227–244 | doi=10.1080/00241160600799846| bibcode = 2006Letha..39..227H | url = http://doc.rero.ch/record/16190/files/PAL_E3399.pdf }}</ref> Even if they had been able to bend their necks upward to that degree (which they could not), gravity would have tipped their body forward and kept most of the heavy neck in the water.

On 12 August 2011, researchers from the U.S. described a fossil of a pregnant plesiosaur found on a Kansas ranch in 1987.<ref>{{cite journal|author=F. R. O’Keefe1,*, L. M. Chiappe2 |url=https://www.science.org/doi/abs/10.1126/science.1205689 |title=Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur (Reptilia, Sauropterygia) |journal=Science |year=2011 |volume=333 |issue=6044 |pages=870–873 |publisher=Sciencemag.org |doi=10.1126/science.1205689 |pmid=21836013 |bibcode=2011Sci...333..870O |s2cid=36165835 |access-date=2011-08-15|url-access=subscription }}</ref> The plesiosauroid, ''Polycotylus latippinus'', has confirmed that these predatory marine reptiles gave birth to single, large, live offspring—contrary to other marine reptile reproduction which typically involves a large number of small babies. Before this study, plesiosauroids had sometimes been portrayed crawling out of water to lay eggs in the manner of sea turtles, but experts had long suspected that their anatomy was not compatible with movement on land. The adult plesiosaur measures {{cvt|4|m|ft}} long and the juvenile is {{cvt|1.5|m|ft}} long.<ref>{{cite web |author=Anthony King |url=http://www.cosmosmagazine.com/news/4615/ancient-sea-dragons-had-a-caring-side |title=Ancient sea dragons had a caring side |publisher=Cosmosmagazine.com |access-date=2011-08-15 |url-status=dead |archive-url=https://web.archive.org/web/20111001200222/http://www.cosmosmagazine.com/news/4615/ancient-sea-dragons-had-a-caring-side |archive-date=2011-10-01 }}</ref>

==References==
{{Reflist|30em|refs=
<ref name="cedaro-gast-occ-168">"Occurrence of Gastroliths in Mesozoic Taxa," in Sanders et al. (2001). Page 168.</ref>
}}

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{{refend}}

==External links==
*[https://www.foxnews.com/story/possibly-complete-plesiosaur-skeleton-found-in-arctic Fox News: Possibly Complete Plesiosaur Skeleton Found in Arctic]
* ''[http://www.plesiosaur.com/ The Plesiosaur Site]''. Richard Forrest.
* ''[http://www.plesiosauria.com/ The Plesiosaur Directory]''. Dr Adam Stuart Smith.
* ''[http://www.plesiosauria.com/news/index.php/the-name-game-plesiosaur-ia-oidea-idae-or-us/ The name game: plesiosaur-ia, -oidea, -idae, or -us?]''.
* ''[http://www.oceansofkansas.com/plesiosaur.html Oceans of Kansas Paleontology]''. Mike Everhart.
* ''[http://www.oceansofkansas.com/Ples-roam.html Where the elasmosaurs roam: Separating fact from fiction]''. Mike Everhart.
* ''[http://www.the-scientist.com/news/20041118/01 Triassic reptiles had live young]''
*[http://www.bbc.co.uk/northyorkshire/news/2002/10/23/plesiosaur.shtml The Filey (Yorkshire) Plesiosaur 2002 (part 1)]
*[http://news.bbc.co.uk/1/hi/england/north_yorkshire/5213182.stm The Filey (Yorkshire) Plesiosaur 2002 (part 2)]
* [https://www.nsf.gov/news/news_summ.jsp?cntn_id=108228 Antarctic Researchers to Discuss Difficult Recovery of Unique Juvenile Plesiosaur Fossil], from the National Science Foundation, December 6, 2006.
* "[https://archive.today/20110604040628/http://www.timesonline.co.uk/printFriendly/0,,1-2-527486,00.html Fossil hunters turn up 50-ton monster of prehistoric deep]". Allan Hall and Mark Henderson. ''Times Online'', December 30, 2002. (Monster of Aramberri)
{{Plesiosauria|Pliosauroidea}}

{{Taxonbar|from=Q1619550}}

[[Category:Plesiosaurs]]
[[Category:Taxa named by John Edward Gray]]
[[Category:Pliensbachian first appearances]]
[[Category:Maastrichtian extinctions]]
[[Category:Plesiosauroids| ]]