Polycotylidae

Polycotylidae Temporal range: Late Cretaceous, 99.5–66.5 Ma PreЄ Є O S D C P T J K Pg N
Trinacromerum bentonianum from the Late Cretaceous of Kansas
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Clade:	†Leptocleidia
Family:	†Polycotylidae Williston, 1909
Subgroups
See text.

Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae.

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 Plesiosauridae and Elasmosauridae. They have been found worldwide, with specimens reported from New Zealand, Australia, Japan, Morocco, the USA, Canada, the former states of the USSR and South America.^[1]

Phylogeny

Dolichorynchops (Trinacromerum) bonneri in the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado

Cladogram after Albright, Gillette and Titus (2007).^[2]

Plesiosauria	Plesiosaurus Tricleidus  Polycotylidae  Edgarosaurus Thililua  Palmulainae  UMUT MV 19965 (from Japan) Pahasapasaurus (=AMM 98.1.1)[3] Palmulasaurus  Polycotylinae  Dolichorhynchops Trinacromerum Eopolycotylus Polycotylus

Cladogram after Ketchum and Benson (2010).^[4]

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

Below is a cladogram of polycotylid relationships from Ketchum & Benson, 2011.^[5]

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

External links

• Palæos: The Vertebrates, Lepidosauromorpha: Cryptocleidoidea: Tricleidia

References

1. Druckenmiller, Patrick S. and 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. doi:10.1666/09-014.1.
2. 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. Journal of Vertebrate Paleontology, v. 27, n. 1, p. 41-58.
3. 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.
4. Ketchum, H. F., and 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: 361–392. doi:10.1111/j.1469-185X.2009.00107.x. PMID 20002391.
5. Hilary F. Ketchum and 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. doi:10.1111/j.1475-4983.2011.01083.x.