"[3] In an alternative classification scheme, paleontologist Michael Maisch restricted Shastasauridae to the genus Shastasaurus and placed Shonisaurus and Besanosaurus in separate families, Shonisauridae and Besanosauridae, respectively.

In 2018, Dean Lomax, de la Salle, Judy Massare, and Ramues Gallois identified the Lilstock specimen as a shastasaurid.

Using Shonisaurus sikanniensis as a model, the researchers estimated the ichthyosaur to have been 26 meters (85 ft) long, nearly the size of a blue whale.

[11] Evidence for this prey diversity includes gut contents from Guizhouichthyosarus tangae, Shonisaurus popularis, and an unnamed specimen from the Brooks Range of Alaska.

[11] Although older studies have suggested that shastasaurids were suction-feeders, 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,[12] and since some species like Shonisaurus had robust sectorial teeth with gut contents of mollusk shells and vertebrates.