Picrocleidus Explained

Picrocleidus is an extinct genus of plesiosaur from the Middle Jurassic Oxford Clay Formation (Callovian stage) of the United Kingdom.

Discovery and naming

The holotype was discovered in the Oxford Clay Formation in Peterborough, England.^{[1] [2]} It was initially assigned to Muraenosaurus as M. beloclis by Seeley (1892).^[3] M. beloclis was moved to its own genus Picrocleidus by Andrews (1910).^[4]

Two specimens are known:

The holotype specimen BMNH R2429, consisting of posterior cervical vertebrae, pectorals and the first dorsal, some dorsal ribs, the shoulder-girdle, and the left humerus.

And specimen BMNH R2739, consisting of a basisphenoid and parasphenoid, cervical vertebrae, sacrals with the sacral ribs, an anterior caudal, some ventral ribs, both radii, odd paddle-bones, portions of ilia, ischia, and pubes.

Classification

Picrocleidus has previously been considered synonymous with Muraenosaurus although there are doubts in the relationship between the two groupings.^[5]

Picrocleidus is currently classified as a member of the Cryptoclididae.

See also

• Timeline of plesiosaur research

Notes and References

1. Benson . R. B. J. . Druckenmiller . P. S. . 10.1111/brv.12038 . Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition . Biological Reviews . 1–23. 2013 . 23581455. 89. 1 . 19710180 .
2. Andrews, Charles W. (1910). A descriptive catalogue of the marine reptiles of the Oxford Clay, Part 2. British Museum (Nat. Soc.) 13:139-149.
3. Seeley . Harry G. . 1892 . The nature of the shoulder girdle and clavicular arch in sauropterygia . Proceedings of the Royal Society of London . 51 . 308-314 . 119–151 . 10.1098/rspl.1892.0017 . 0370-1662.
4. Muraenosaurus? Reedii, Sp. Nov. and Tricleidus? Laramiensis Knight, American Jurassic Plesiosaurs. The Journal of Geology, 20, 4, 344-352.
5. Wilhelm BC. (2010). A New Partial Skeleton of a Cryptocleidoid Plesiosaur from the Upper Jurassic Sundance Formation of Wyoming. Journal of Vertebrate Paleontology , 30, 6, 1736-1742.