List of plesiosaur genera
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This list of plesiosaurs is a comprehensive listing of all genera that have ever been included in the order Plesiosauria, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered plesiosaurs. The list currently includes 176 genera.
Scope and terminology
There is no official, canonical list of plesiosaur genera but one of the most thorough attempts can be found on the Plesiosauria section of Mikko Haaramo's Phylogeny Archive; also pertinent is the Plesiosaur Genera section at Adam Stuart Smith's Plesiosaur Directory.
Naming conventions and terminology follow the International Code of Zoological Nomenclature. Technical terms used include:
- Junior synonym: A name which describes the same taxon as a previously published name. If two or more genera are formally designated and the type specimens are later assigned to the same genus, the first to be published (in chronological order) is the senior synonym, and all other instances are junior synonyms. Senior synonyms are generally used, except by special decision of the ICZN, but junior synonyms cannot be used again, even if deprecated. Junior synonymy is often subjective, unless the genera described were both based on the same type specimen.
- Nomen nudum (Latin for "naked name"): A name that has appeared in print but has not yet been formally published by the standards of the ICZN. Nomina nuda (the plural form) are invalid, and are therefore not italicized as a proper generic name would be. If the name is later formally published, that name is no longer a nomen nudum and will be italicized on this list. Often, the formally published name will differ from any nomina nuda that describe the same specimen. In this case, these nomina nuda will be deleted from this list in favor of the published name.
- Preoccupied name: A name that is formally published, but which has already been used for another taxon. This second use is invalid (as are all subsequent uses) and the name must be replaced. As preoccupied names are not valid generic names, they will also go unitalicized on this list.
- Nomen dubium (Latin for "dubious name"): A name describing a fossil with no unique diagnostic features. As this can be an extremely subjective and controversial designation, this term is not used on this list.
The list
| Genus Authors Year Status Age Location Notes Images Abyssosaurus Berezin 2011 Valid Early Cretaceous Russia Had a uniquely short, triangular skull with extremely large eye sockets; shows potential adaptations for specialized deep-diving lifestyle Acostasaurus Gómez-Pérez & Noè 2017 Valid Early Cretaceous Colombia Noted for its unusually caniniform dentition compared to other pliosaurids Albertonectes Kubo et al. 2012 Valid Late Cretaceous Canada Had the longest neck of any known plesiosaur, made up of seventy-six vertebrae Alexandronectes Otero et al. 2016 Valid Late Cretaceous New Zealand The first aristonectine from which a stapes is known Alexeyisaurus Sennikov & Arkhangelsky 2010 Dubious Late Triassic Russia Although originally described as an elasmosaurid plesiosaur, it was suggested to be an undiagnostic sauropterygian taxon by subsequent analyses Alzadasaurus Welles & Bump 1949 Jr. synonym N/A N/A Junior synonym of Styxosaurus Anguanax Cau & Fanti 2015 Valid Late Jurassic Italy Several features of its skull would indicate a diet of soft or small-bodied prey Anningasaura Vincent & Benson 2012 Valid Early Jurassic United Kingdom Known from a partial skeleton belonging to a juvenile animal Apatomerus Williston 1903 Dubious? Early Cretaceous United States Originally identified as a crocodilian and later reinterpreted as a pterosaur, although it may very likely be a plesiosaur Aphrosaurus Welles 1943 Valid Late Cretaceous United States Distinguished by the presence of a deepened ventral notch along the centra of its cervical vertebrae Apractocleidus Smellie 1915 Jr. synonym N/A N/A Junior synonym of Cryptoclidus Aptychodon von Reuss 1855 Valid Late Cretaceous Czech Republic Some studies suggest this genus may be a potential junior synonym of Polyptychodon Archaeonectrus Novozhilov 1964 Valid Early Jurassic United Kingdom Originally mistakenly believed to be a species of Plesiosaurus Aristonectes Cabrera 1941 Valid Late Cretaceous Antarctica Argentina Chile This genus would have migrated regularly between Patagonia and Antarctica as implied by its fossil record Arminisaurus Sachs & Kear 2017 Valid Early Jurassic Germany Shares some features of its skeleton with leptocleidian plesiosauroids Attenborosaurus Bakker 1993 Valid Early Jurassic United Kingdom Named in honor of British broadcaster and naturalist David Attenborough Atychodracon Smith 2015 Valid Late Triassic to Early Jurassic United Kingdom Has been assigned to four different genera before its formal description Avalonnectes Benson, Evans & Druckenmiller 2012 Valid Early Jurassic United Kingdom One of the oldest plesiosaurs known to date Bathyspondylus Delair 1982 Valid Late Jurassic United Kingdom Possesses an unusual mix of pliosauroid and plesiosauroid features Bishanopliosaurus Dong 1980 Valid Early Jurassic to Middle Jurassic China Could be distinguished by the bifurcated ribs of its sacrum Borealonectes Sato & Wu 2008 Valid Middle Jurassic Canada One of the few North American plesiosaurs that lived during the Jurassic Boyacasaurus Benavides-Cabra et al. 2025 Valid Early Cretaceous Colombia Known from two specimens found in association with ammonites Brachauchenius Williston 1903 Valid Late Cretaceous Morocco United States Several pliosaurid specimens of same age had been referred to this genus, although they were either renamed as new taxa or considered dubious Brancasaurus Wegner 1914 Valid Early Cretaceous Germany Its cervical vertebrae are noted for having shark fin-shaped neural spines Brimosaurus Leidy 1854 Dubious Late Cretaceous United States May be synonymous with Cimoliasaurus Callawayasaurus Carpenter 1999 Valid Early Cretaceous Colombia Has no pectoral bars, a trait shared with Terminonatator Cardiocorax Araújo et al. 2015 Valid Late Cretaceous Angola The morphology of its scapula suggests a relatively unique swimming style for this genus Ceraunosaurus Thurmond 1968 Jr. synonym N/A N/A Junior synonym of Trinacromerum Chubutinectes O'Gorman et al. 2023 Valid Late Cretaceous Argentina Larger than the contemporary Kawanectes due to its marine habitat Cimoliasaurus Leidy 1851 Valid Late Cretaceous United States Discovered in sediments that superficially resemble the chalk deposits found in the Western Interior Seaway Colymbosaurus Seeley 1874 Valid Middle Jurassic to Late Jurassic Norway United Kingdom The holotype humerus was originally misidentified as a femur Crymocetus Cope 1869 Dubious Late Cretaceous United Kingdom Today seen as an indeterminate plesiosaur. Only known from a single vertebra Cryonectes Vincent, Bardet & Mattioli 2012 Valid Early Jurassic France Possessed a relatively elongated snout Cryptoclidus Seeley 1892 Valid Middle Jurassic to Late Jurassic United Kingdom Would have preyed on small, soft-bodied animals as indicated by the delicate build of its skull and teeth Discosaurus Leidy 1851 Valid Late Cretaceous United States Has been argued to be the same taxon as Elasmosaurus Djupedalia Knutsen, Druckenmiller & Hurum 2012 Valid Late Jurassic Norway Named after former Minister of Education and Research Øystein Djupedal Dolichorhynchops Williston 1902 Valid Late Cretaceous Canada United States Described two years after its discovery Dravidosaurus Yadagiri & Ayyasami 1979 Dubious Late Cretaceous India Suggested to be either an ornithischian (potentially stegosaurian) dinosaur or a plesiosaur Eardasaurus Ketchum & Benson 2022 Valid Middle Jurassic United Kingdom Had prominent enamel ridges in its teeth, which would indicate a diet of large prey Edgarosaurus Druckenmiller 2002 Valid Early Cretaceous United States One of the first polycotylids to become native to the Western Interior Seaway Eiectus Noè & Gómez-Pérez 2021 Valid? Early Cretaceous Australia Potentially synonymous with Kronosaurus Elasmosaurus Cope 1868 Valid Late Cretaceous United States Originally erroneously reconstructed with its skull placed at the end of its tail Embaphias Cope 1894 Dubious Late Cretaceous United States Based on three cervical vertebrae Eoplesiosaurus Benson, Evans & Druckenmiller 2012 Valid Early Jurassic United Kingdom May have been the basalmost known member of the Plesiosauroidea Eopolycotylus Albright et al. 2007 Valid Late Cretaceous United States Known from a single partial skeleton Eretmosaurus Seeley 1874 Valid Early Jurassic to Middle Jurassic Russia United Kingdom Two species are known Eromangasaurus Kear 2005 Valid Early Cretaceous Australia The holotype skull is almost complete although badly crushed Eurycleidus Andrews 1922 Valid Early Jurassic United Kingdom May have made a powerful forward stroke for fast swimming as suggested by its relatively large shoulder bones Eurysaurus Gaudry 1878 Valid Early Jurassic France Formerly misidentified as a nothosaur Fluvionectes Campbell et al. 2021 Valid Late Cretaceous Canada The holotype specimen may have died in a log jam as suggested by the pieces of coalified wood found alongside it Franconiasaurus Sachs, Eggmaier & Madzia 2024 Valid Early Jurassic Germany Its cervical and dorsal vertebrae possessed short neural spines Fresnosaurus Welles 1943 Valid Late Cretaceous United States Coexisted with at least three other plesiosaurs Futabasaurus Sato, Hasegawa & Manabe 2006 Valid Late Cretaceous Japan Most of its bones preserve bite marks caused by Cretalamna, indicating it would have been scavenged or hunted by the shark Gallardosaurus Gasparini 2009 Valid Late Jurassic Cuba The only known individual was discovered in a concretion in dark shale "Georgia" Otschev 1976 Preoccupied N/A N/A Preoccupied by a genus of snake, later renamed Georgiasaurus Georgiasaurus Otschev 1977 Valid Late Cretaceous Russia The holotype skeleton was damaged during preparation of the quarry stone Gondwananectes Otero et al. 2026 Valid Middle Jurassic Chile May be the sister taxon to the Cryptoclidia Goniosaurus Meyer 1860 Valid Late Cretaceous Netherlands The striations of its tooth meet each other under an angle pointing to the root instead of the apex Gronausaurus Hampe 2013 Jr. synonym N/A N/A Junior synonym of Brancasaurus Hastanectes Benson et al. 2012 Valid Early Cretaceous United Kingdom Originally named as a species of Cimoliasaurus Hauffiosaurus O'Keefe 2001 Valid Early Jurassic Germany United Kingdom The holotype specimen is preserved lying on its back Hydralmosaurus Welles 1943 Jr. synonym N/A N/A Junior synonym of Styxosaurus Hydrorion Großmann 2007 Valid Early Jurassic Germany Several individuals are known Hydrotherosaurus Welles 1943 Valid Late Cretaceous United States Multiple vertebrae were the first remains to be found. More bones had been unearthed afterwards Ischyrodon von Meyer 1838 Dubious Middle Jurassic Switzerland Has been considered a junior synonym of Liopleurodon, but a 2022 revision found some differences that would make it separate from that genus Jucha Fischer et al. 2020 Valid Early Cretaceous Russia One of the earliest known confirmed elasmosaurids Kaiwhekea Cruickshank & Fordyce 2002 Valid Late Cretaceous New Zealand Preserved inside a large, roughly 6.5 m (21 ft) long concretion Kawanectes O'Gorman 2016 Valid Late Cretaceous Argentina Previously identified as a species of Trinacromerum Kimmerosaurus Brown 1981 Valid Late Jurassic Norway? United Kingdom Its skull was overall similar to that of the related Cryptoclidus but much broader Kronosaurus Longman 1924 Valid Early Cretaceous Australia One of the largest pliosaurids ever identified, likely the apex predator of its environment Lagenanectes Sachs, Hornung & Kear 2017 Valid Early Cretaceous Germany One of the most well-preserved plesiosaurs known from the Early Cretaceous of Europe Leivanectes Páramo-Fonseca et al. 2019 Valid Early Cretaceous Colombia Differs from the contemporary Callawayasaurus, hence its classification as a separate genus Leptocleidus Andrews 1922 Valid Early Cretaceous Australia South Africa United Kingdom Like other members of its family and unlike most other plesiosaurs, it inhabited freshwater environments Leurospondylus Brown 1913 Valid Late Cretaceous Canada Its exact taxonomic placement is uncertain Libonectes Carpenter 1997 Valid Late Cretaceous Morocco United States Originally referred to as a species of Elasmosaurus, but it was named as a distinct genus due to morphological differences Lindwurmia Vincent & Storrs 2019 Valid Early Jurassic Germany Possessed five pairs of premaxillary teeth Liopleurodon Sauvage 1873 Valid Middle Jurassic to Late Jurassic France Germany Mexico United Kingdom Several analyses suggest that this genus may have been an ambush predator Lorrainosaurus Sachs et al. 2023 Valid Middle Jurassic France Originally assigned to Simolestes but it has been found to be more derived Luetkesaurus Kiprijanoff 1883 Dubious Late Cretaceous Russia No species name has ever been assigned Luskhan Fischer et al. 2017 Valid Early Cretaceous Russia Unlike other pliosaurids, it had a slender snout, small teeth, and short tooth rows, convergent with polycotylids Lusonectes Smith, Araújo & Mateus 2012 Valid Early Jurassic Portugal The first plesiosaur named from Portugal Macroplata Swinton 1930 Valid Early Jurassic United Kingdom Its neck is comparatively longer than its head Makhaira Fischer et al. 2015 Valid Early Cretaceous Russia Unusually, its teeth were triangular in cross-section Manemergus Buchy et al. 2005 Valid Late Cretaceous Morocco May have been contemporaneous with Thililua Marambionectes O'Gorman et al. 2024 Valid Late Cretaceous Antarctica Closely allied to the aristonectines Maresaurus Gasparini 1997 Valid Middle Jurassic Argentina The first plesiosaur identified from the Los Molles Formation Marmornectes Ketchum & Benson 2011 Valid Middle Jurassic United Kingdom Would have been very similar to Peloneustes Martinectes Clark, O'Keefe & Slack 2023 Valid Late Cretaceous Russia? United States Initially named as species of Trinacromerum and then assigned to Dolichorhynchops until its reclassification as a new genus in 2023 Mauisaurus Hector 1874 Dubious Late Cretaceous New Zealand Several specimens had been referred to this genus, but a 2017 review restricts it only to the lectotype Mauriciosaurus Frey et al. 2017 Valid Late Cretaceous Mexico Similarly to Cryptoclidus, it is noted for the unusual arrangement of gastralia Megacephalosaurus Schumacher et al. 2013 Valid Late Cretaceous United States One of the last known pliosaurids prior to their extinction Megalneusaurus Knight 1898 Valid Late Jurassic United States One specimen preserves stomach contents, including cephalopods and fish Meyerasaurus Smith & Vincent 2010 Valid Early Jurassic Germany Represented by a complete, articulated skeleton Microcleidus Watson 1909 Valid Early Jurassic France Germany Luxembourg United Kingdom Possessed at least forty vertebrae in its neck Monquirasaurus Noè & Gómez-Pérez 2021 Valid Early Cretaceous Colombia One of the largest pliosaurids. Originally known as a South American species of Kronosaurus Morenosaurus Welles 1943 Valid Late Cretaceous United States The only described specimen is nearly complete, missing only the skull and some parts of the neck and paddles Morturneria Chatterjee & Creisler 1994 Valid Late Cretaceous Antarctica Once considered to be a juvenile Aristonectes, but a 2017 study found it to be distinct enough to warrant recognition as separate Muraenosaurus Seeley 1874 Valid Middle Jurassic United Kingdom May have possessed an increased muscle attachment towards its neck as indicated by its elongated cervical vertebrae with broad neural spines Nakonanectes Serratos et al. 2017 Valid Late Cretaceous United States Its overall morphology was exceptionally similar to that of aristonectines despite being less derived Nichollssaura Druckenmiller & Russell 2009 Valid Early Cretaceous Canada Fills a temporal gap of approximately 40 million years in the fossil record of North American plesiosaurs "Nichollsia" Druckenmiller & Russell 2008 Preoccupied N/A N/A Preoccupied by a genus of isopod, renamed Nichollssaura Occitanosaurus Bardet et al. 1999 Jr. synonym N/A N/A Junior synonym of Microcleidus Ogmodirus Williston & Moodie 1913 Dubious Late Cretaceous United States May be an elasmosaurid Oligosimus Leidy 1872 Jr. synonym N/A N/A Junior synonym of Cimoliasaurus Opallionectes Kear 2006 Valid Early Cretaceous Australia Hypothesized to live on a cold habitat Ophthalmothule Roberts et al. 2020 Valid Late Jurassic to Early Cretaceous Norway May have possibly hunted at night and/or in the bathypelagic zone as suggested by its relatively large eye sockets and similar features as Abyssosaurus Orophosaurus Cope 1851 Dubious Late Cretaceous United States Named based only on portions of three neck vertebrae Pachycostasaurus Cruickshank et al. 1996 Valid Middle Jurassic United Kingdom Its skeleton bears several unique features in most of the bones Pahasapasaurus Schumacher 2007 Valid Late Cretaceous United States Distinguishable by characters of its epipodial and palate bones "Palmula" Albright et al. 2007 Preoccupied N/A N/A Preoccupied by a genus of foraminifer, renamed Palmulasaurus Palmulasaurus Albright et al. 2007 Valid Late Cretaceous United States Shared its environment with three other polycotylids Pantosaurus Marsh 1893 Valid Late Jurassic United States One fossil preserves a partially digested ichthyosaur embryo within its stomach cavity Peloneustes Lydekker 1889 Valid Middle Jurassic United Kingdom Multiple specimens are known, including fairly complete material, which make it one of the most well-known pliosaurids Peyerus Stromer 1935 Jr. synonym N/A N/A Junior synonym of Leptocleidus Picrocleidus Andrews 1910 Valid Middle Jurassic United Kingdom Previously synonymized with the coeval Muraenosaurus, but this has been cast into doubt Piptomerus Cope 1887 Jr. synonym N/A N/A Junior synonym of Cimoliasaurus Piratosaurus Leidy 1865 Dubious Late Cretaceous Canada Solely known from a single tooth which may have come from a polycotylid Plesioelasmosaurus Schumacher & Everhart 2022 Valid Late Cretaceous United States Would have been relatively basal for an elasmosaurid Plesionectes Sachs & Madzia 2025 Valid Early Jurassic Germany Preserved patches of soft tissue impressions that may indicate a dark coloration for this taxon Plesiopharos Puértolas-Pascual et al. 2021 Valid Early Jurassic Portugal The holotype was discovered next to a lighthouse Plesiopleurodon Carpenter 1996 Valid Late Cretaceous United States Initially believed to be a member of the Pliosauroidea Plesiopterys O'Keefe 2004 Valid Early Jurassic Germany Displays an unusual combination of primitive and derived traits Plesiosaurus De la Beche & Conybeare 1821 Valid Early Jurassic United Kingdom The first plesiosaur genus scientifically named and described. May be the most commonly found member in the Lias Group Pliosaurus Owen 1841 Valid Late Jurassic to Early Cretaceous Norway Russia Ukraine United Kingdom One of the largest pliosaurids. The second specimen of P. funkei has been nicknamed "Predator X" Polycotylus Cope 1869 Valid Late Cretaceous Russia United States One particular specimen preserves a fetus inside of it, suggesting it gave live birth Polyptychodon Owen 1841 Dubious Late Cretaceous Argentina? France? United Kingdom The sauropod dinosaur Dinodocus had been mistakenly attributed to this genus "Raptocleidus" Evans 2012 Nomen nudum Early Jurassic United Kingdom Two species have been named, albeit informally Rhaeticosaurus Wintrich et al. 2017 Valid Late Triassic Germany One of the few plesiosaurs known from the Triassic Rhomaleosaurus Seeley 1874 Valid Early Jurassic United Kingdom One of the largest early predatory marine reptiles. Four species are known Sachicasaurus Páramo-Fonseca et al. 2018 Valid Early Cretaceous Colombia One of the largest and most completely known pliosaurids yet described Scalamagnus Clark, O'Keefe & Slack 2023 Valid Late Cretaceous United States Once believed to be a species of Dolichorhynchops Scanisaurus Persson 1959 Dubious Late Cretaceous Russia Sweden Although it is now considered dubious, this genus continues to be used in practice Seeleyosaurus White 1940 Valid Early Jurassic Germany Russia? Remains originally identified as Plesiosaurus Serpentisuchops Persons, Street & Kelley 2022 Valid Late Cretaceous United States Had an exceptionally long neck, a unique trait among polycotylids Simolestes Andrews 1909 Valid Middle Jurassic to Late Jurassic India? United Kingdom Possessed an unusually short, high skull Sinopliosaurus Young 1944 Dubious Early Cretaceous China Based only on a tooth and three vertebrae Spitrasaurus Knutsen, Druckenmiller & Hurum 2012 Valid Late Jurassic Norway United Kingdom? Two species have been named Spondylosaurus Fischer 1845 Jr. synonym N/A N/A Junior synonym of Pliosaurus Stenorhynchosaurus Páramo-Fonseca et al. 2016 Valid Early Cretaceous Colombia Originally identified as a specimen of Brachauchenius "Stereosaurus" Seeley 1869 Nomen nudum Late Cretaceous United Kingdom An informally named plesiosaur Sthenarosaurus Watson 1909 Valid Early Jurassic United Kingdom Its pelvis was relatively broad and strong Stratesaurus Benson, Evans & Druckenmiller 2012 Valid Early Jurassic United Kingdom Possibly the basalmost known rhomaleosaurid Stretosaurus Tarlo 1959 Jr. synonym N/A N/A Junior synonym of Pliosaurus Strongylokrotaphus Novozhilov 1964 Jr. synonym N/A N/A Junior synonym of Pliosaurus Styxosaurus Welles 1943 Valid Late Cretaceous United States Closely related to Elasmosaurus, but can be differentiated from it based on morphological features Sulcusuchus Gasparini & Spalletti 1990 Valid Late Cretaceous Argentina Originally mistakenly believed to be a pseudosuchian Taphrosaurus Cope 1870 Dubious Late Cretaceous United States Poorly known Tatenectes O'Keefe & Wahl 2003 Valid Late Jurassic United States Its unusual body shape and pachyostotic gastralia would have made it more suitable to turbulence Terminonatator Sato 2003 Valid Late Cretaceous Canada One of the youngest plesiosaurs known from the Western Interior Seaway Thalassiodracon Storrs & Taylor 1996 Valid Late Triassic to Early Jurassic United Kingdom Its maxillae had heterodont dentition Thalassiosaurus Welles 1953 Jr. synonym N/A N/A Junior synonym of Styxosaurus Thalassomedon Welles 1943 Valid Late Cretaceous United States The type specimen has stones preserved in its stomach cavity Thalassonomosaurus Welles 1943 Jr. synonym N/A N/A Junior synonym of Styxosaurus Thaumatodracon Smith & Araújo 2017 Valid Early Jurassic United Kingdom Relatively large for a rhomaleosaurid Thaumatosaurus von Meyer 1841 Jr. synonym N/A N/A The holotype is dubious and not diagnostic, as it can be referred to as an indeterminate pliosauroid. The specimens that were assigned to this genus now belong to different taxa Thililua Bardet, Suberbiola & Jalil 2003 Valid Late Cretaceous Morocco The first polycotylid plesiosaur named from Africa Traskasaura O'Keefe et al. 2025 Valid Late Cretaceous Canada Before its formal scientific description, it has been variously referred to as the "Courtenay elasmosaur", "Puntledge elasmosaur", or "Haslam elasmosaur". Officially recognized as the Provincial Fossil of British Columbia Tremamesacleis White 1940 Jr. synonym N/A N/A Junior synonym of Muraenosaurus Trematospondylus Quenstedt 1858 Dubious Middle Jurassic Germany One of the first described plesiosaurs. Known only from seven large vertebrae Tricleidus Andrews 1909 Valid Middle Jurassic United Kingdom One referred species has been later found to belong to Colymbosaurus Trinacromerum Cragin 1888 Valid Late Cretaceous Canada United States May have preyed on small fish as suggested by its dentition Tuarangisaurus Wiffen, Wiffen & Moisley 1986 Valid Late Cretaceous New Zealand Possesses two features in its skeleton that are otherwise unknown in other elasmosaurids "Turneria" Chatterjee & Small 1989 Preoccupied N/A N/A Preoccupied by a genus of ant, renamed Morturneria Umoonasaurus Kear, Schroeder & Lee 2006 Valid Early Cretaceous Australia Uniquely for a plesiosaur, its skull features three crest-ridges that were likely covered in keratin Unktaheela Clark, O'Keefe & Slack 2023 Valid Late Cretaceous United States The smallest adult polycotylid yet known Uronautes Cope 1876 Dubious Late Cretaceous United States Described as a rhomaleosaurid but its extremely late age casts doubt into this Vectocleidus Benson et al. 2012 Valid Early Cretaceous United Kingdom Previously thought to belong to its relative Leptocleidus Vegasaurus O'Gorman et al. 2015 Valid Late Cretaceous Antarctica May be closely related to Morenosaurus Vinialesaurus Gasparini et al. 2002 Valid Late Jurassic Cuba Originally referred to as a species of Cryptoclidus, but it was distinct enough from that genus to be named as its own taxon Wapuskanectes Druckenmiller & Russell 2006 Valid Early Cretaceous Canada The oldest known elasmosaurid from North America Westphaliasaurus Schwermann & Sander 2011 Valid Early Jurassic Germany Known from an articulated, almost complete skeleton Woolungasaurus Persson 1960 Dubious Early Cretaceous Australia Today considered an indeterminate elasmosaurid Wunyelfia Otero et al. 2021 Valid Late Cretaceous Chile One of the few Patagonian plesiosaurs described from outside Argentina Yuzhoupliosaurus Zhang 1985 Valid Middle Jurassic China Distinguishable by its long coracoids and well-developed clavicles Zarafasaura Vincent et al. 2011 Valid Late Cretaceous Morocco Unlike other elasmosaurids, its skull was unusually short | ||||||||
| Genus | Authors | Year | Status | Age | Location | Notes | Images | |
| Abyssosaurus | Berezin | 2011 | Valid | Early Cretaceous | Russia | Had a uniquely short, triangular skull with extremely large eye sockets; shows potential adaptations for specialized deep-diving lifestyle | ||
| Acostasaurus | Gómez-Pérez & Noè | 2017 | Valid | Early Cretaceous | Colombia | Noted for its unusually caniniform dentition compared to other pliosaurids | ||
| Albertonectes | Kubo et al. | 2012 | Valid | Late Cretaceous | Canada | Had the longest neck of any known plesiosaur, made up of seventy-six vertebrae | ||
| Alexandronectes | Otero et al. | 2016 | Valid | Late Cretaceous | New Zealand | The first aristonectine from which a stapes is known | ||
| Alexeyisaurus | Sennikov & Arkhangelsky | 2010 | Dubious | Late Triassic | Russia | Although originally described as an elasmosaurid plesiosaur, it was suggested to be an undiagnostic sauropterygian taxon by subsequent analyses | ||
| Alzadasaurus | Welles & Bump | 1949 | Jr. synonym | N/A | N/A | Junior synonym of Styxosaurus | ||
| Anguanax | Cau & Fanti | 2015 | Valid | Late Jurassic | Italy | Several features of its skull would indicate a diet of soft or small-bodied prey | ||
| Anningasaura | Vincent & Benson | 2012 | Valid | Early Jurassic | United Kingdom | Known from a partial skeleton belonging to a juvenile animal | ||
| Apatomerus | Williston | 1903 | Dubious? | Early Cretaceous | United States | Originally identified as a crocodilian and later reinterpreted as a pterosaur, although it may very likely be a plesiosaur | ||
| Aphrosaurus | Welles | 1943 | Valid | Late Cretaceous | United States | Distinguished by the presence of a deepened ventral notch along the centra of its cervical vertebrae | ||
| Apractocleidus | Smellie | 1915 | Jr. synonym | N/A | N/A | Junior synonym of Cryptoclidus | ||
| Aptychodon | von Reuss | 1855 | Valid | Late Cretaceous | Czech Republic | Some studies suggest this genus may be a potential junior synonym of Polyptychodon | ||
| Archaeonectrus | Novozhilov | 1964 | Valid | Early Jurassic | United Kingdom | Originally mistakenly believed to be a species of Plesiosaurus | ||
| Aristonectes | Cabrera | 1941 | Valid | Late Cretaceous | Antarctica Argentina Chile | This genus would have migrated regularly between Patagonia and Antarctica as implied by its fossil record | ||
| Arminisaurus | Sachs & Kear | 2017 | Valid | Early Jurassic | Germany | Shares some features of its skeleton with leptocleidian plesiosauroids | ||
| Attenborosaurus | Bakker | 1993 | Valid | Early Jurassic | United Kingdom | Named in honor of British broadcaster and naturalist David Attenborough | ||
| Atychodracon | Smith | 2015 | Valid | Late Triassic to Early Jurassic | United Kingdom | Has been assigned to four different genera before its formal description | ||
| Avalonnectes | Benson, Evans & Druckenmiller | 2012 | Valid | Early Jurassic | United Kingdom | One of the oldest plesiosaurs known to date | ||
| Bathyspondylus | Delair | 1982 | Valid | Late Jurassic | United Kingdom | Possesses an unusual mix of pliosauroid and plesiosauroid features | ||
| Bishanopliosaurus | Dong | 1980 | Valid | Early Jurassic to Middle Jurassic | China | Could be distinguished by the bifurcated ribs of its sacrum | ||
| Borealonectes | Sato & Wu | 2008 | Valid | Middle Jurassic | Canada | One of the few North American plesiosaurs that lived during the Jurassic | ||
| Boyacasaurus | Benavides-Cabra et al. | 2025 | Valid | Early Cretaceous | Colombia | Known from two specimens found in association with ammonites | ||
| Brachauchenius | Williston | 1903 | Valid | Late Cretaceous | Morocco United States | Several pliosaurid specimens of same age had been referred to this genus, although they were either renamed as new taxa or considered dubious | ||
| Brancasaurus | Wegner | 1914 | Valid | Early Cretaceous | Germany | Its cervical vertebrae are noted for having shark fin-shaped neural spines | ||
| Brimosaurus | Leidy | 1854 | Dubious | Late Cretaceous | United States | May be synonymous with Cimoliasaurus | ||
| Callawayasaurus | Carpenter | 1999 | Valid | Early Cretaceous | Colombia | Has no pectoral bars, a trait shared with Terminonatator | ||
| Cardiocorax | Araújo et al. | 2015 | Valid | Late Cretaceous | Angola | The morphology of its scapula suggests a relatively unique swimming style for this genus | ||
| Ceraunosaurus | Thurmond | 1968 | Jr. synonym | N/A | N/A | Junior synonym of Trinacromerum | ||
| Chubutinectes | O'Gorman et al. | 2023 | Valid | Late Cretaceous | Argentina | Larger than the contemporary Kawanectes due to its marine habitat | ||
| Cimoliasaurus | Leidy | 1851 | Valid | Late Cretaceous | United States | Discovered in sediments that superficially resemble the chalk deposits found in the Western Interior Seaway | ||
| Colymbosaurus | Seeley | 1874 | Valid | Middle Jurassic to Late Jurassic | Norway United Kingdom | The holotype humerus was originally misidentified as a femur | ||
| Crymocetus | Cope | 1869 | Dubious | Late Cretaceous | United Kingdom | Today seen as an indeterminate plesiosaur. Only known from a single vertebra | ||
| Cryonectes | Vincent, Bardet & Mattioli | 2012 | Valid | Early Jurassic | France | Possessed a relatively elongated snout | ||
| Cryptoclidus | Seeley | 1892 | Valid | Middle Jurassic to Late Jurassic | United Kingdom | Would have preyed on small, soft-bodied animals as indicated by the delicate build of its skull and teeth | ||
| Discosaurus | Leidy | 1851 | Valid | Late Cretaceous | United States | Has been argued to be the same taxon as Elasmosaurus | ||
| Djupedalia | Knutsen, Druckenmiller & Hurum | 2012 | Valid | Late Jurassic | Norway | Named after former Minister of Education and Research Øystein Djupedal | ||
| Dolichorhynchops | Williston | 1902 | Valid | Late Cretaceous | Canada United States | Described two years after its discovery | ||
| Dravidosaurus | Yadagiri & Ayyasami | 1979 | Dubious | Late Cretaceous | India | Suggested to be either an ornithischian (potentially stegosaurian) dinosaur or a plesiosaur | ||
| Eardasaurus | Ketchum & Benson | 2022 | Valid | Middle Jurassic | United Kingdom | Had prominent enamel ridges in its teeth, which would indicate a diet of large prey | ||
| Edgarosaurus | Druckenmiller | 2002 | Valid | Early Cretaceous | United States | One of the first polycotylids to become native to the Western Interior Seaway | ||
| Eiectus | Noè & Gómez-Pérez | 2021 | Valid? | Early Cretaceous | Australia | Potentially synonymous with Kronosaurus | ||
| Elasmosaurus | Cope | 1868 | Valid | Late Cretaceous | United States | Originally erroneously reconstructed with its skull placed at the end of its tail | ||
| Embaphias | Cope | 1894 | Dubious | Late Cretaceous | United States | Based on three cervical vertebrae | ||
| Eoplesiosaurus | Benson, Evans & Druckenmiller | 2012 | Valid | Early Jurassic | United Kingdom | May have been the basalmost known member of the Plesiosauroidea | ||
| Eopolycotylus | Albright et al. | 2007 | Valid | Late Cretaceous | United States | Known from a single partial skeleton | ||
| Eretmosaurus | Seeley | 1874 | Valid | Early Jurassic to Middle Jurassic | Russia United Kingdom | Two species are known | ||
| Eromangasaurus | Kear | 2005 | Valid | Early Cretaceous | Australia | The holotype skull is almost complete although badly crushed | ||
| Eurycleidus | Andrews | 1922 | Valid | Early Jurassic | United Kingdom | May have made a powerful forward stroke for fast swimming as suggested by its relatively large shoulder bones | ||
| Eurysaurus | Gaudry | 1878 | Valid | Early Jurassic | France | Formerly misidentified as a nothosaur | ||
| Fluvionectes | Campbell et al. | 2021 | Valid | Late Cretaceous | Canada | The holotype specimen may have died in a log jam as suggested by the pieces of coalified wood found alongside it | ||
| Franconiasaurus | Sachs, Eggmaier & Madzia | 2024 | Valid | Early Jurassic | Germany | Its cervical and dorsal vertebrae possessed short neural spines | ||
| Fresnosaurus | Welles | 1943 | Valid | Late Cretaceous | United States | Coexisted with at least three other plesiosaurs | ||
| Futabasaurus | Sato, Hasegawa & Manabe | 2006 | Valid | Late Cretaceous | Japan | Most of its bones preserve bite marks caused by Cretalamna, indicating it would have been scavenged or hunted by the shark | ||
| Gallardosaurus | Gasparini | 2009 | Valid | Late Jurassic | Cuba | The only known individual was discovered in a concretion in dark shale | ||
| "Georgia" | Otschev | 1976 | Preoccupied | N/A | N/A | Preoccupied by a genus of snake, later renamed Georgiasaurus | ||
| Georgiasaurus | Otschev | 1977 | Valid | Late Cretaceous | Russia | The holotype skeleton was damaged during preparation of the quarry stone | ||
| Gondwananectes | Otero et al. | 2026 | Valid | Middle Jurassic | Chile | May be the sister taxon to the Cryptoclidia | ||
| Goniosaurus | Meyer | 1860 | Valid | Late Cretaceous | Netherlands | The striations of its tooth meet each other under an angle pointing to the root instead of the apex | ||
| Gronausaurus | Hampe | 2013 | Jr. synonym | N/A | N/A | Junior synonym of Brancasaurus | ||
| Hastanectes | Benson et al. | 2012 | Valid | Early Cretaceous | United Kingdom | Originally named as a species of Cimoliasaurus | ||
| Hauffiosaurus | O'Keefe | 2001 | Valid | Early Jurassic | Germany United Kingdom | The holotype specimen is preserved lying on its back | ||
| Hydralmosaurus | Welles | 1943 | Jr. synonym | N/A | N/A | Junior synonym of Styxosaurus | ||
| Hydrorion | Großmann | 2007 | Valid | Early Jurassic | Germany | Several individuals are known | ||
| Hydrotherosaurus | Welles | 1943 | Valid | Late Cretaceous | United States | Multiple vertebrae were the first remains to be found. More bones had been unearthed afterwards | ||
| Ischyrodon | von Meyer | 1838 | Dubious | Middle Jurassic | Switzerland | Has been considered a junior synonym of Liopleurodon, but a 2022 revision found some differences that would make it separate from that genus | ||
| Jucha | Fischer et al. | 2020 | Valid | Early Cretaceous | Russia | One of the earliest known confirmed elasmosaurids | ||
| Kaiwhekea | Cruickshank & Fordyce | 2002 | Valid | Late Cretaceous | New Zealand | Preserved inside a large, roughly 6.5 m (21 ft) long concretion | ||
| Kawanectes | O'Gorman | 2016 | Valid | Late Cretaceous | Argentina | Previously identified as a species of Trinacromerum | ||
| Kimmerosaurus | Brown | 1981 | Valid | Late Jurassic | Norway? United Kingdom | Its skull was overall similar to that of the related Cryptoclidus but much broader | ||
| Kronosaurus | Longman | 1924 | Valid | Early Cretaceous | Australia | One of the largest pliosaurids ever identified, likely the apex predator of its environment | ||
| Lagenanectes | Sachs, Hornung & Kear | 2017 | Valid | Early Cretaceous | Germany | One of the most well-preserved plesiosaurs known from the Early Cretaceous of Europe | ||
| Leivanectes | Páramo-Fonseca et al. | 2019 | Valid | Early Cretaceous | Colombia | Differs from the contemporary Callawayasaurus, hence its classification as a separate genus | ||
| Leptocleidus | Andrews | 1922 | Valid | Early Cretaceous | Australia South Africa United Kingdom | Like other members of its family and unlike most other plesiosaurs, it inhabited freshwater environments | ||
| Leurospondylus | Brown | 1913 | Valid | Late Cretaceous | Canada | Its exact taxonomic placement is uncertain | ||
| Libonectes | Carpenter | 1997 | Valid | Late Cretaceous | Morocco United States | Originally referred to as a species of Elasmosaurus, but it was named as a distinct genus due to morphological differences | ||
| Lindwurmia | Vincent & Storrs | 2019 | Valid | Early Jurassic | Germany | Possessed five pairs of premaxillary teeth | ||
| Liopleurodon | Sauvage | 1873 | Valid | Middle Jurassic to Late Jurassic | France Germany Mexico United Kingdom | Several analyses suggest that this genus may have been an ambush predator | ||
| Lorrainosaurus | Sachs et al. | 2023 | Valid | Middle Jurassic | France | Originally assigned to Simolestes but it has been found to be more derived | ||
| Luetkesaurus | Kiprijanoff | 1883 | Dubious | Late Cretaceous | Russia | No species name has ever been assigned | ||
| Luskhan | Fischer et al. | 2017 | Valid | Early Cretaceous | Russia | Unlike other pliosaurids, it had a slender snout, small teeth, and short tooth rows, convergent with polycotylids | ||
| Lusonectes | Smith, Araújo & Mateus | 2012 | Valid | Early Jurassic | Portugal | The first plesiosaur named from Portugal | ||
| Macroplata | Swinton | 1930 | Valid | Early Jurassic | United Kingdom | Its neck is comparatively longer than its head | ||
| Makhaira | Fischer et al. | 2015 | Valid | Early Cretaceous | Russia | Unusually, its teeth were triangular in cross-section | ||
| Manemergus | Buchy et al. | 2005 | Valid | Late Cretaceous | Morocco | May have been contemporaneous with Thililua | ||
| Marambionectes | O'Gorman et al. | 2024 | Valid | Late Cretaceous | Antarctica | Closely allied to the aristonectines | ||
| Maresaurus | Gasparini | 1997 | Valid | Middle Jurassic | Argentina | The first plesiosaur identified from the Los Molles Formation | ||
| Marmornectes | Ketchum & Benson | 2011 | Valid | Middle Jurassic | United Kingdom | Would have been very similar to Peloneustes | ||
| Martinectes | Clark, O'Keefe & Slack | 2023 | Valid | Late Cretaceous | Russia? United States | Initially named as species of Trinacromerum and then assigned to Dolichorhynchops until its reclassification as a new genus in 2023 | ||
| Mauisaurus | Hector | 1874 | Dubious | Late Cretaceous | New Zealand | Several specimens had been referred to this genus, but a 2017 review restricts it only to the lectotype | ||
| Mauriciosaurus | Frey et al. | 2017 | Valid | Late Cretaceous | Mexico | Similarly to Cryptoclidus, it is noted for the unusual arrangement of gastralia | ||
| Megacephalosaurus | Schumacher et al. | 2013 | Valid | Late Cretaceous | United States | One of the last known pliosaurids prior to their extinction | ||
| Megalneusaurus | Knight | 1898 | Valid | Late Jurassic | United States | One specimen preserves stomach contents, including cephalopods and fish | ||
| Meyerasaurus | Smith & Vincent | 2010 | Valid | Early Jurassic | Germany | Represented by a complete, articulated skeleton | ||
| Microcleidus | Watson | 1909 | Valid | Early Jurassic | France Germany Luxembourg United Kingdom | Possessed at least forty vertebrae in its neck | ||
| Monquirasaurus | Noè & Gómez-Pérez | 2021 | Valid | Early Cretaceous | Colombia | One of the largest pliosaurids. Originally known as a South American species of Kronosaurus | ||
| Morenosaurus | Welles | 1943 | Valid | Late Cretaceous | United States | The only described specimen is nearly complete, missing only the skull and some parts of the neck and paddles | ||
| Morturneria | Chatterjee & Creisler | 1994 | Valid | Late Cretaceous | Antarctica | Once considered to be a juvenile Aristonectes, but a 2017 study found it to be distinct enough to warrant recognition as separate | ||
| Muraenosaurus | Seeley | 1874 | Valid | Middle Jurassic | United Kingdom | May have possessed an increased muscle attachment towards its neck as indicated by its elongated cervical vertebrae with broad neural spines | ||
| Nakonanectes | Serratos et al. | 2017 | Valid | Late Cretaceous | United States | Its overall morphology was exceptionally similar to that of aristonectines despite being less derived | ||
| Nichollssaura | Druckenmiller & Russell | 2009 | Valid | Early Cretaceous | Canada | Fills a temporal gap of approximately 40 million years in the fossil record of North American plesiosaurs | ||
| "Nichollsia" | Druckenmiller & Russell | 2008 | Preoccupied | N/A | N/A | Preoccupied by a genus of isopod, renamed Nichollssaura | ||
| Occitanosaurus | Bardet et al. | 1999 | Jr. synonym | N/A | N/A | Junior synonym of Microcleidus | ||
| Ogmodirus | Williston & Moodie | 1913 | Dubious | Late Cretaceous | United States | May be an elasmosaurid | ||
| Oligosimus | Leidy | 1872 | Jr. synonym | N/A | N/A | Junior synonym of Cimoliasaurus | ||
| Opallionectes | Kear | 2006 | Valid | Early Cretaceous | Australia | Hypothesized to live on a cold habitat | ||
| Ophthalmothule | Roberts et al. | 2020 | Valid | Late Jurassic to Early Cretaceous | Norway | May have possibly hunted at night and/or in the bathypelagic zone as suggested by its relatively large eye sockets and similar features as Abyssosaurus | ||
| Orophosaurus | Cope | 1851 | Dubious | Late Cretaceous | United States | Named based only on portions of three neck vertebrae | ||
| Pachycostasaurus | Cruickshank et al. | 1996 | Valid | Middle Jurassic | United Kingdom | Its skeleton bears several unique features in most of the bones | ||
| Pahasapasaurus | Schumacher | 2007 | Valid | Late Cretaceous | United States | Distinguishable by characters of its epipodial and palate bones | ||
| "Palmula" | Albright et al. | 2007 | Preoccupied | N/A | N/A | Preoccupied by a genus of foraminifer, renamed Palmulasaurus | ||
| Palmulasaurus | Albright et al. | 2007 | Valid | Late Cretaceous | United States | Shared its environment with three other polycotylids | ||
| Pantosaurus | Marsh | 1893 | Valid | Late Jurassic | United States | One fossil preserves a partially digested ichthyosaur embryo within its stomach cavity | ||
| Peloneustes | Lydekker | 1889 | Valid | Middle Jurassic | United Kingdom | Multiple specimens are known, including fairly complete material, which make it one of the most well-known pliosaurids | ||
| Peyerus | Stromer | 1935 | Jr. synonym | N/A | N/A | Junior synonym of Leptocleidus | ||
| Picrocleidus | Andrews | 1910 | Valid | Middle Jurassic | United Kingdom | Previously synonymized with the coeval Muraenosaurus, but this has been cast into doubt | ||
| Piptomerus | Cope | 1887 | Jr. synonym | N/A | N/A | Junior synonym of Cimoliasaurus | ||
| Piratosaurus | Leidy | 1865 | Dubious | Late Cretaceous | Canada | Solely known from a single tooth which may have come from a polycotylid | ||
| Plesioelasmosaurus | Schumacher & Everhart | 2022 | Valid | Late Cretaceous | United States | Would have been relatively basal for an elasmosaurid | ||
| Plesionectes | Sachs & Madzia | 2025 | Valid | Early Jurassic | Germany | Preserved patches of soft tissue impressions that may indicate a dark coloration for this taxon | ||
| Plesiopharos | Puértolas-Pascual et al. | 2021 | Valid | Early Jurassic | Portugal | The holotype was discovered next to a lighthouse | ||
| Plesiopleurodon | Carpenter | 1996 | Valid | Late Cretaceous | United States | Initially believed to be a member of the Pliosauroidea | ||
| Plesiopterys | O'Keefe | 2004 | Valid | Early Jurassic | Germany | Displays an unusual combination of primitive and derived traits | ||
| Plesiosaurus | De la Beche & Conybeare | 1821 | Valid | Early Jurassic | United Kingdom | The first plesiosaur genus scientifically named and described. May be the most commonly found member in the Lias Group | ||
| Pliosaurus | Owen | 1841 | Valid | Late Jurassic to Early Cretaceous | Norway Russia Ukraine United Kingdom | One of the largest pliosaurids. The second specimen of P. funkei has been nicknamed "Predator X" | ||
| Polycotylus | Cope | 1869 | Valid | Late Cretaceous | Russia United States | One particular specimen preserves a fetus inside of it, suggesting it gave live birth | ||
| Polyptychodon | Owen | 1841 | Dubious | Late Cretaceous | Argentina? France? United Kingdom | The sauropod dinosaur Dinodocus had been mistakenly attributed to this genus | ||
| "Raptocleidus" | Evans | 2012 | Nomen nudum | Early Jurassic | United Kingdom | Two species have been named, albeit informally | ||
| Rhaeticosaurus | Wintrich et al. | 2017 | Valid | Late Triassic | Germany | One of the few plesiosaurs known from the Triassic | ||
| Rhomaleosaurus | Seeley | 1874 | Valid | Early Jurassic | United Kingdom | One of the largest early predatory marine reptiles. Four species are known | ||
| Sachicasaurus | Páramo-Fonseca et al. | 2018 | Valid | Early Cretaceous | Colombia | One of the largest and most completely known pliosaurids yet described | ||
| Scalamagnus | Clark, O'Keefe & Slack | 2023 | Valid | Late Cretaceous | United States | Once believed to be a species of Dolichorhynchops | ||
| Scanisaurus | Persson | 1959 | Dubious | Late Cretaceous | Russia Sweden | Although it is now considered dubious, this genus continues to be used in practice | ||
| Seeleyosaurus | White | 1940 | Valid | Early Jurassic | Germany Russia? | Remains originally identified as Plesiosaurus | ||
| Serpentisuchops | Persons, Street & Kelley | 2022 | Valid | Late Cretaceous | United States | Had an exceptionally long neck, a unique trait among polycotylids | ||
| Simolestes | Andrews | 1909 | Valid | Middle Jurassic to Late Jurassic | India? United Kingdom | Possessed an unusually short, high skull | ||
| Sinopliosaurus | Young | 1944 | Dubious | Early Cretaceous | China | Based only on a tooth and three vertebrae | ||
| Spitrasaurus | Knutsen, Druckenmiller & Hurum | 2012 | Valid | Late Jurassic | Norway United Kingdom? | Two species have been named | ||
| Spondylosaurus | Fischer | 1845 | Jr. synonym | N/A | N/A | Junior synonym of Pliosaurus | ||
| Stenorhynchosaurus | Páramo-Fonseca et al. | 2016 | Valid | Early Cretaceous | Colombia | Originally identified as a specimen of Brachauchenius | ||
| "Stereosaurus" | Seeley | 1869 | Nomen nudum | Late Cretaceous | United Kingdom | An informally named plesiosaur | ||
| Sthenarosaurus | Watson | 1909 | Valid | Early Jurassic | United Kingdom | Its pelvis was relatively broad and strong | ||
| Stratesaurus | Benson, Evans & Druckenmiller | 2012 | Valid | Early Jurassic | United Kingdom | Possibly the basalmost known rhomaleosaurid | ||
| Stretosaurus | Tarlo | 1959 | Jr. synonym | N/A | N/A | Junior synonym of Pliosaurus | ||
| Strongylokrotaphus | Novozhilov | 1964 | Jr. synonym | N/A | N/A | Junior synonym of Pliosaurus | ||
| Styxosaurus | Welles | 1943 | Valid | Late Cretaceous | United States | Closely related to Elasmosaurus, but can be differentiated from it based on morphological features | ||
| Sulcusuchus | Gasparini & Spalletti | 1990 | Valid | Late Cretaceous | Argentina | Originally mistakenly believed to be a pseudosuchian | ||
| Taphrosaurus | Cope | 1870 | Dubious | Late Cretaceous | United States | Poorly known | ||
| Tatenectes | O'Keefe & Wahl | 2003 | Valid | Late Jurassic | United States | Its unusual body shape and pachyostotic gastralia would have made it more suitable to turbulence | ||
| Terminonatator | Sato | 2003 | Valid | Late Cretaceous | Canada | One of the youngest plesiosaurs known from the Western Interior Seaway | ||
| Thalassiodracon | Storrs & Taylor | 1996 | Valid | Late Triassic to Early Jurassic | United Kingdom | Its maxillae had heterodont dentition | ||
| Thalassiosaurus | Welles | 1953 | Jr. synonym | N/A | N/A | Junior synonym of Styxosaurus | ||
| Thalassomedon | Welles | 1943 | Valid | Late Cretaceous | United States | The type specimen has stones preserved in its stomach cavity | ||
| Thalassonomosaurus | Welles | 1943 | Jr. synonym | N/A | N/A | Junior synonym of Styxosaurus | ||
| Thaumatodracon | Smith & Araújo | 2017 | Valid | Early Jurassic | United Kingdom | Relatively large for a rhomaleosaurid | ||
| Thaumatosaurus | von Meyer | 1841 | Jr. synonym | N/A | N/A | The holotype is dubious and not diagnostic, as it can be referred to as an indeterminate pliosauroid. The specimens that were assigned to this genus now belong to different taxa | ||
| Thililua | Bardet, Suberbiola & Jalil | 2003 | Valid | Late Cretaceous | Morocco | The first polycotylid plesiosaur named from Africa | ||
| Traskasaura | O'Keefe et al. | 2025 | Valid | Late Cretaceous | Canada | Before its formal scientific description, it has been variously referred to as the "Courtenay elasmosaur", "Puntledge elasmosaur", or "Haslam elasmosaur". Officially recognized as the Provincial Fossil of British Columbia | ||
| Tremamesacleis | White | 1940 | Jr. synonym | N/A | N/A | Junior synonym of Muraenosaurus | ||
| Trematospondylus | Quenstedt | 1858 | Dubious | Middle Jurassic | Germany | One of the first described plesiosaurs. Known only from seven large vertebrae | ||
| Tricleidus | Andrews | 1909 | Valid | Middle Jurassic | United Kingdom | One referred species has been later found to belong to Colymbosaurus | ||
| Trinacromerum | Cragin | 1888 | Valid | Late Cretaceous | Canada United States | May have preyed on small fish as suggested by its dentition | ||
| Tuarangisaurus | Wiffen, Wiffen & Moisley | 1986 | Valid | Late Cretaceous | New Zealand | Possesses two features in its skeleton that are otherwise unknown in other elasmosaurids | ||
| "Turneria" | Chatterjee & Small | 1989 | Preoccupied | N/A | N/A | Preoccupied by a genus of ant, renamed Morturneria | ||
| Umoonasaurus | Kear, Schroeder & Lee | 2006 | Valid | Early Cretaceous | Australia | Uniquely for a plesiosaur, its skull features three crest-ridges that were likely covered in keratin | ||
| Unktaheela | Clark, O'Keefe & Slack | 2023 | Valid | Late Cretaceous | United States | The smallest adult polycotylid yet known | ||
| Uronautes | Cope | 1876 | Dubious | Late Cretaceous | United States | Described as a rhomaleosaurid but its extremely late age casts doubt into this | ||
| Vectocleidus | Benson et al. | 2012 | Valid | Early Cretaceous | United Kingdom | Previously thought to belong to its relative Leptocleidus | ||
| Vegasaurus | O'Gorman et al. | 2015 | Valid | Late Cretaceous | Antarctica | May be closely related to Morenosaurus | ||
| Vinialesaurus | Gasparini et al. | 2002 | Valid | Late Jurassic | Cuba | Originally referred to as a species of Cryptoclidus, but it was distinct enough from that genus to be named as its own taxon | ||
| Wapuskanectes | Druckenmiller & Russell | 2006 | Valid | Early Cretaceous | Canada | The oldest known elasmosaurid from North America | ||
| Westphaliasaurus | Schwermann & Sander | 2011 | Valid | Early Jurassic | Germany | Known from an articulated, almost complete skeleton | ||
| Woolungasaurus | Persson | 1960 | Dubious | Early Cretaceous | Australia | Today considered an indeterminate elasmosaurid | ||
| Wunyelfia | Otero et al. | 2021 | Valid | Late Cretaceous | Chile | One of the few Patagonian plesiosaurs described from outside Argentina | ||
| Yuzhoupliosaurus | Zhang | 1985 | Valid | Middle Jurassic | China | Distinguishable by its long coracoids and well-developed clavicles | ||
| Zarafasaura | Vincent et al. | 2011 | Valid | Late Cretaceous | Morocco | Unlike other elasmosaurids, its skull was unusually short |
See also
Footnotes
- Haaramo, Mikko (15 November 2005). . Mikko's Phylogeny Archive. Archived from on 2 September 2006.
- Smith, Adam Stuart. . The Plesiosaur Directory. Archived from on 21 March 2006.