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Polycotylids Temporal range: Early - Late Cretaceous, 113–72 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Martinectes in the Rocky Mountain Dinosaur Resource Center
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Clade:	†Leptocleidia
Family:	†Polycotylidae Williston, 1909
Genera
†Edgarosaurus †Manemergus †Mauriciosaurus †Piratosaurus? †Rarosaurus? †Thililua †Occultonectia †Plesiopleurodon †Sulcusuchus †Palmulasaurinae †Pahasapasaurus †Palmulasaurus †Polycotylinae †Eopolycotylus †Georgiasaurus †Polycotylus †Scalamagnus †Serpentisuchops †Trinacromerum †Dolichorhynchia †Dolichorhynchops †Martinectes †Unktaheela

Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. They are known as false pliosaurs. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. Several species survived into the final stage of the Cretaceous, the early Maastrichtian around 72 million years ago. The possible latest surviving member Rarosaurus from the late Maastrichtian is more likely a crocodylomorph.

With their short necks and large elongated heads, they resemble the pliosaurs, but closer phylogenetic studies indicate that they share many common features with the Leptocleididae and Elasmosauridae. They have been found worldwide, with specimens reported from New Zealand, Australia, Japan, Morocco, the US, Canada, Eastern Europe, and South America.

Phylogeny

Cladogram after Albright, Gillette and Titus (2007).

Cladogram after Ketchum and Benson (2010).

Below is a cladogram of polycotylid relationships from Ketchum & Benson, 2011.

References

1. V. Fischer; R. B. J. Benson; P. S. Druckenmiller; H. F. Ketchum; N. Bardet (2018). "The evolutionary history of polycotylid plesiosaurians". Royal Society Open Science. 5 (3): 172177. Bibcode:2018RSOS....572177F. doi:10.1098/rsos.172177. PMC 5882735. PMID 29657811.
2. Clark, Robert O.; O’Keefe, F. Robin; Slack, Sara E. (2023-12-24). "A new genus of small polycotylid plesiosaur from the Upper Cretaceous of the Western Interior Seaway and a clarification of the genus Dolichorhynchops". Cretaceous Research. 157: 105812. doi:10.1016/j.cretres.2023.105812. ISSN 0195-6671.
3. Fischer, V.; Benson, R. B. J.; Druckenmiller, P. S.; Ketchum, H. F.; Bardet, N. (March 2018). "The evolutionary history of polycotylid plesiosaurians". Royal Society Open Science. 5 (3): 172177. Bibcode:2018RSOS....572177F. doi:10.1098/rsos.172177. ISSN 2054-5703. PMC 5882735. PMID 29657811.
4. Alhalabi, W. A.; Bardet, N.; Sachs, S.; Kear, B. P.; Joude, I. B.; Yazbek, M. K.; Godoy, P. L.; Langer, M. C. (2024). "Recovering lost time in Syria: New Late Cretaceous (Coniacian-Santonian) elasmosaurid remains from the Palmyrides mountain chain". Cretaceous Research. 159. 105871. Bibcode:2024CrRes.15905871A. doi:10.1016/j.cretres.2024.105871.
5. Druckenmiller, Patrick S. & Russell, Anthony P. (2009). "Earliest North American Occurrence Of Polycotylidae (Sauropterygia: Plesiosauria) From The Lower Cretaceous (Albian) Clearwater Formation, Alberta, Canada" (PDF). Journal of Paleontology. 83 (6): 361–392. Bibcode:2009JPal...83..981D. doi:10.1666/09-014.1. S2CID 130695434. Archived from the original (PDF) on 2011-07-06.
6. Albright III, L. B., Gillette, D. D., and Titus, A. L., 2007b. Plesiosaurs from the Upper Cretaceous (Cenomanian-Turonian) Tropic Shale of southern Utah, part 2: polycotylidae Archived 2011-09-28 at the Wayback Machine. Journal of Vertebrate Paleontology, v. 27, n. 1, p. 41-58.
7. Schumacher, B. A., 2007, A new polycotylid plesiosaur (Reptilia; Sauropterygia) from the Greenhorn Limestone (Upper Cretaceous; lower upper Cenomanian), Black Hills, South Dakota: In: The Geology and Paleontology of the Late Cretaceous marine deposits of the Dakotas, edited by Martin, J. E., and Parris, D. C., The Geological Society of America, Special Paper 427, p. 133-146.
8. Ketchum, H. F. & Benson, R. B. J. (2010). "Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylogenetic analyses". Biological Reviews. 85 (2): 361–392. doi:10.1111/j.1469-185X.2009.00107.x. PMID 20002391. S2CID 12193439.
9. Hilary F. Ketchum; Roger B. J. Benson (2011). "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". Special Papers in Palaeontology. 86: 109–129.

External links

• Palæos: The Vertebrates, Lepidosauromorpha: Cryptocleidoidea: Tricleidia

v t e Sauropterygia
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Subclass: Diapsida Clade: Neodiapsida Sauropsida see Sauropsida Sauropterygia see below↓
Sauropterygia Sauropterygia Alexeyisaurus Atopodentatus Palatodonta? Pomolispondylus? Hanosaurus? Helveticosauridae? Eusaurosphargis? Helveticosaurus Saurosphargidae Hemilopas? Largocephalosaurus Prosaurosphargis Saurosphargis Sinosaurosphargis Stauromatodon? Placodontia Paraplacodus Pararcus Placodus Cyamodontoidea Cyamodus Glyphoderma Henodus Macroplacus Parahenodus Placochelys Protenodontosaurus Psephochelys Psephoderma Psephosauriscus Psephosaurus Sinocyamodus Eosauropterygia see below↓
Eosauropterygia Eosauropterygia Corosaurus Cymatosaurus Pachypleurosauria Anarosaurus Chusaurus Dactylosaurus Dawazisaurus? Diandongosaurus Dianmeisaurus Dianopachysaurus Hanosaurus? Honghesaurus Keichousaurus Luopingosaurus Majiashanosaurus Neusticosaurus Odoiporosaurus Prosantosaurus Panzhousaurus Qianxisaurus Serpianosaurus Wumengosaurus Nothosauroidea Brevicaudosaurus Hispaniasaurus? Sanchiaosaurus Simosauridae Paludidraco Simosaurus Nothosauridae Ceresiosaurus Germanosaurus Lariosaurus Metanothosaurus Nothosaurus Proneusticosaurus Silvestrosaurus Pistosauroidea Augustasaurus Bobosaurus Chinchenia Kwangsisaurus Pistosaurus Tanaisosaurus Wangosaurus Yunguisaurus Plesiosauria see below↓
Plesiosauria Plesiosauria Anningasaura Bathyspondylus Bobosaurus? Lindwurmia Sinopliosaurus Termatosaurus? Rhomaleosauridae Anningasaura? Archaeonectrus Atychodracon Avalonnectes Bishanopliosaurus? Borealonectes Eurycleidus Lindwurmia? Macroplata Maresaurus Meyerasaurus Rhomaleosaurus Sthenarosaurus Stratesaurus Thaumatodracon Yuzhoupliosaurus? Pliosauridae Anguanax Arminisaurus Attenborosaurus Cryonectes Hauffiosaurus Marmornectes Pachycostasaurus Rhaeticosaurus Thalassiodracon Thalassophonea Eardasaurus Gallardosaurus Liopleurodon Lorrainosaurus Megalneusaurus UANL-FCT-R2? Peloneustes "Pliosaurus" andrewsi Pliosaurus Simolestes Brachaucheninae Acostasaurus Brachauchenius Eiectus Kronosaurus Luskhan Makhaira Megacephalosaurus Monquirasaurus Polyptychodon Sachicasaurus Stenorhynchosaurus Plesiosauroidea Eoplesiosaurus Eretmosaurus Franconiasaurus Leurospondylus Plesiopharos Plesiopterys Plesiosaurus Westphaliasaurus Microcleididae Hydrorion Lusonectes Microcleidus Occitanosaurus Seeleyosaurus Cryptoclidia see below↓
Cryptoclidia Cryptoclididae Opallionectes Colymbosaurinae Abyssosaurus Colymbosaurus Djupedalia Pantosaurus Spitrasaurus Cryptoclidinae Cryptoclidus Kimmerosaurus Ophthalmothule Tatenectes Muraenosaurinae Muraenosaurus Picrocleidus Tricleidus? Vinialesaurus Xenopsaria Leptocleidia Hastanectes? Nichollssaura? Leptocleididae Brancasaurus Hastanectes? Leptocleidus Nichollssaura? Umoonasaurus? Vectocleidus Polycotylidae Edgarosaurus Manemergus Mauriciosaurus Thililua Palmulasaurinae Pahasapasaurus? Palmulasaurus Occultonectia Plesiopleurodon Sulcusuchus Polycotylinae Eopolycotylus Georgiasaurus Polycotylus Scalamagnus Serpentisuchops Trinacromerum Dolichorhynchia Dolichorhynchops Martinectes Unktaheela Elasmosauridae Callawayasaurus Cimoliasaurus Eromangasaurus Goniosaurus Jucha Lagenanectes Leivanectes Mauisaurus Ogmodirus Orophosaurus Plesioelasmosaurus Scanisaurus Wapuskanectes Woolungasaurus Euelasmosaurida Cardiocorax Libonectes Thalassomedon Elasmosaurinae Albertonectes Elasmosaurus Fluvionectes Hydrotherosaurus? Nakonanectes Styxosaurus Terminonatator Weddellonectia Aphrosaurus Chubutinectes Futabasaurus Fresnosaurus? Hydrotherosaurus? Kawanectes Marambionectes Morenosaurus Tuarangisaurus Vegasaurus Zarafasaura? Aristonectinae Alexandronectes Aristonectes Kaiwhekea Morturneria Wunyelfia

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