Reexamination of _Shastasaurus neoscapularis_ demonstrates that it's
significantly different from the type species of the genus (which are
regarded as nomina dubia - thus _Shastasaurus_ is poorly founded) -
e.g. in morphology of the frontals - and needs a new genus, named here
_Metashastasaurus_. In a cladistic analysis, a monophyletic
Shastasauridae is found: _Mixosaurus_ and (monophyletic)
_Cymbospondylus_ are successive sister taxa to _Besanosaurus_ +
(_Shastasaurus_ + (_Shonisaurus_ + Metashastasaurus_)).