| Picrocleidus | |
|---|---|
| Fossils from both specimens ofP. beloclis | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Order: | †Plesiosauria |
| Superfamily: | †Plesiosauroidea |
| Family: | †Cryptoclididae |
| Genus: | †Picrocleidus Andrews, 1910 |
| Type species | |
| †Muraenosaurus beloclis Seeley, 1892 | |
Picrocleidus is anextinctgenus ofplesiosaur from theMiddle JurassicOxford Clay Formation (Callovian stage) of theUnited Kingdom.

Theholotype was discovered in theOxford Clay Formation inPeterborough, England and acquired byAlfred Nicholson Leeds.[1][2] It was initially assigned toMuraenosaurus asM. beloclis bySeeley in 1892.[3] The specific name means "arrow clavicle", referring to the triangularinterclavicula.M. beloclis was moved to its own genusPicrocleidus byCharles William Andrews in 1910.[2][4] The generic name is derived from Greekpikros, "sharp", enkleis, "key", again referring to the clavicles.
Five specimens are known:
Theholotype specimenBMNH R1965, a postcranial skeleton.
Specimen BMNH R3698, a skeleton with skull, including a complete tail.
Specimen BMNH R2429, an old individual consisting of anterior and posterior cervical vertebrae, pectorals and the first dorsal, some dorsal ribs, the shoulder-girdle, and the left humerus.[2]
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.[1]
Specimen HM 2981666: a young individual.
Picrocleidus has previously been considered synonymous withMuraenosaurus although there are doubts in the relationship between the two groupings.[5]
Picrocleidus is currently classified as a member of theCryptoclididae.[4]