''Colymbosaurus'' is a genus of

cryptoclidid Cryptoclididae is a family of medium-sized plesiosaurs that existed from the Middle Jurassic to the Early Cretaceous. They had long necks, broad and short skulls and densely packed teeth. They fed on small soft-bodied preys such as small fish and ...

plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

from the Late Jurassic ( Callovian-

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...

) of the UK and

Svalbard Svalbard ( , ), also known as Spitsbergen, or Spitzbergen, is a Norwegian archipelago in the Arctic Ocean. North of mainland Europe, it is about midway between the northern coast of Norway and the North Pole. The islands of the group range ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

. There are two currently recognized species, ''C. megadeirus'' and ''C. svalbardensis''. Both species are relatively medium-sized plesiosaurs, reaching in length and in body mass.

Taxonomy

The first remains attributate to ''Colymbosaurus'' were described as a new species of '' Plesiosaurus'', ''P. trochantericus''. The holotype of the species, NHMUK 31787, a

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

(upper arm bone), comes from the Kimmeridgian Kimmeridge Clay Formation of

Shotover Shotover is a hill and forest in Oxfordshire, England. The hill is east of Oxford. Its highest point is above sea level. Early history The toponym may be derived from the Old English , meaning "steep slope". Shotover was part of the Wychwood ...

Oxfordshire Oxfordshire is a ceremonial and non-metropolitan county in the north west of South East England. It is a mainly rural county, with its largest settlement being the city of Oxford. The county is a centre of research and development, primarily ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Owe ...

, however, misidentified the bone as a femur, an identification corrected in an 1871 publication on the geology of Oxfordshire. In the meantime, other plesiosauroid remains were being described from the Kimmeridge Clay by independent workers. The species ''Plesiosaurus megadeirus'' was coined for two partial postcranial specimens in a publication cataloging Mesozoic tetrapod specimens in the collections of the Sedgwick Museum of Earth Sciences at the

University of Cambridge , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

. The name ''Pliosaurus portlandicus'' was coined for a partial hindlimb from

Dorset Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...

, while John Whitaker Hulke erected the species ''Plesiosaurus manselii'' for an incomplete postcranial skeleton (NHMUK 40106) from Kimmeridge,

. Harry Govier Seeley came to recognize ''Plesiosaurus megadeirus'' as generically distinct, and coined the name ''Colymbosaurus'' for the species. He later referred ''Pliosaurus portlandicus'' and ''Plesiosaurus manselii'' to ''Colymbosaurus'' and considered them distinct from ''C. megadeirus'' based on the morphology of the epipodials. A review of all nominal species of plesiosauroids from the Late Jurassic of England resulted in the recognition of one species of ''Colymbosaurus'', ''C. trochantericus''. ''P. megadeirus'', ''P. portlandicus'', and ''P. manselii'' were synonymized with ''C. trochantericus''. Because no skull remains were known, ''Colymbosaurus'' was considered possibly a senior synonym of ''

Kimmerosaurus ''Kimmerosaurus'' ("lizard from Kimmeridge") is an extinct genus of plesiosaur from the family Cryptoclididae. ''Kimmerosaurus'' is most closely related to ''Tatenectes''. Discovery There are very few fossil remains of ''Kimmerosaurus'' known. ...

'' based on comparisons with referred material of ''Kimmerosaurus''. The distribution of ''Colymbosaurus'' was extended beyond the UK when the Norwegian ''"

Tricleidus ''Tricleidus'' is an extinct genus of cryptoclidid plesiosaur known from only specimen (BMNH R3539) from the middle Jurassic of United Kingdom. It was first named by Andrews in 1909 and the type species is ''Tricleidus seeleyi''. It was a rela ...

" svalbardensis'' was recognized as a valid species of ''Colymbosaurus'', ''C. svalbardensis''. This assignment, along with the discovery of new plesiosauroids from Svalbard, prompted a new revision of Kimmeridge Clay cryptoclidids. ''Plesiosaurus trochantericus'' was declared a ''nomen dubium'', being referable to ''Colymbosaurus'' but indeterminate at the species level, while ''Kimmerosaurus'' and ''Plesiosaurus manselii'' were recognized as distinct. Because of this revision, ''megadeirus'' was resurrected as the epithet of the type species of ''Colymbosaurus''.Benson RBJ, Bowdler T. 2014. Anatomy of Colymbosaurus (Reptilia, Plesiosauria) from the Kimmeridge Clay Formation of the U.K., and high diversity among Late Jurassic plesiosauroids. Journal of Vertebrate Paleontology 34(5), 1053-1071.

References

{{Taxonbar, from=Q5150354 Cryptoclidids Callovian first appearances Late Jurassic extinctions Middle Jurassic plesiosaurs of Europe Late Jurassic plesiosaurs of Europe Jurassic England Fossils of England Jurassic Norway Fossils of Svalbard Agardhfjellet Formation Fossil taxa described in 1874 Taxa named by Harry Seeley Sauropterygian genera

Taxonomy

See also

References