| DIAPSIDA Osborn, 1903 |
| SAUROPTERYGIA Owen, 1860 |
| PLESIOSAURIA De Blainville, 1835 |
| PLESIOSAUROIDEA Welles, 1943 |
| XENOPSARIA Benson & Druckenmiller, 2014 |
| ELASMOSAURIDAE Cope, 1869 |
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