sikanniensis (Nicholls & Manabe, 2004 [originally Shonisaurus]) Shastasaurus ("Mount Shasta lizard") is an extinct genus of ichthyosaur from the Late Triassic.

[5] A second possible species of Shastasaurus, S. sikanniensis, is known from the Pardonet Formation British Columbia, dating to the middle Norian age (about 210 million years ago).

[8] However, current research indicates that the jaws of shastasaurid ichthyosaurs do not fit the suction-feeding profile, since their short and narrow hyoid bones are unsuitable to withstand impact forces for such kind of feeding,[9] and since some species like Shonisaurus had robust sectorial teeth with gut contents of mollusk shells and vertebrates.

Several species of long-snouted ichthyosaur were referred to Shastasaurus based on this misinterpretation, but are now placed in other genera (including Callawayia and Guizhouichthyosaurus).

[8] However, a new juvenile specimen discovered in 2013 shows that the hyoid bone of Guanlingsaurus is much shorter, and considered it as a distinct genus based on phylogenetic analysis.

[17] Specimens belonging to S. sikanniensis have been found in the Pardonet Formation British Columbia, dating to the middle Norian age.

[8] Dubious species that were referred to this genus include S. carinthiacus (Huene, 1925) from the Austrian Alps and S. neubigi (Sander, 1997) from the German Muschelkalk.