Polycotylidae

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.^[3] The possible latest surviving member Rarosaurus from the late Maastrichtian is more likely a crocodylomorph.^[4]

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[1] †Plesiopleurodon †Sulcusuchus †Palmulasaurinae †Pahasapasaurus †Palmulasaurus †Polycotylinae †Eopolycotylus †Georgiasaurus †Polycotylus †Scalamagnus †Serpentisuchops †Trinacromerum †Dolichorhynchia[2] †Dolichorhynchops †Martinectes †Unktaheela

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.^[5]

Phylogeny

Trinacromerum bentonianum from the Late Cretaceous of Kansas

Cladogram after Albright, Gillette and Titus (2007).^[6]

Plesiosauria	Plesiosaurus Tricleidus  Polycotylidae  Edgarosaurus Thililua  Palmulainae  UMUT MV 19965 (from Japan) Pahasapasaurus (=AMM 98.1.1)[7] Palmulasaurus  Polycotylinae  Dolichorhynchops Trinacromerum Eopolycotylus Polycotylus

Cladogram after Ketchum and Benson (2010).^[8]

Plesiosauroidea	Cryptoclididae  Leptocleidia  Leptocleididae  Polycotylidae  Plesiopleurodon Edgarosaurus QM F18041 Eopolycotylus Trinacromerum Dolichorhynchops herschelensis Dolichorhynchops Manemergus Palmulasaurus

Below is a cladogram of polycotylid relationships from Ketchum & Benson, 2011.^[9]

Plesiosauroidea	Cryptoclididae  Leptocleidia  Leptocleididae  Polycotylidae  Edgarosaurus Plesiopleurodon QM F18041 Eopolycotylus Polycotylus Thililua Trinacromerum Manemergus Dolichorhynchops herschelensis Dolichorhynchops Palmulasaurus

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

• paleontology portal