Cymbospondylus

Cymbospondylus petrinus (Leidy 1868, Merriam 1908, Middle Triassic) 29+ feet (8.33m) long was derived from a sister to the much smaller Mixosaurus and was itself a sister to the even larger Guanlingsaurus and Shastasaurus sikanniensis. The long, eel-like body, short flippers and small, long-snouted skull suggest an undulating swimming style.

Motani (1999) nested Cymbospondylus with Mixosaurus as primitive taxa between Chaohusaurus and Besanosaurus.

Leidy J 1868. Notice of some reptilian remains from Nevada: Proceedings of the American Philosophical Society 20:177-178.

Merriam JC 1908. Triassic ichthyosauria with special references to the American forms. Memoirs of the University of California 1: 1-196.

Yin G-Z, Zhou X, Cao Y, Yu Y and Luo Y 2000. A preliminary study on the earlyLate Triassic marine reptiles from Guanling, Guizhou, China. Geology-Geochemisty 28(3):1–23 (Chinese with English abstract).

wiki/Cymbospondylus

Marine Younginiformes

Enaliosauria

Sauropterygia

Placodontia

Thalattosauriformes

Mesosauria