(2021), Cymbospondylus is placed at the very base of Ichthyosauria, outside the more derived members of Hueneosauria (including Mixosauridae and Shastasauridae). In the publication describing C. duelferi, Klein and colleagues recovered that all species from the Fossil Hill Member in Nevada form a clade with one another.
In 2021, Cymbospondylus was positioned as the earliest member of Ichthyosauria, distinct from more advanced members of Hueneosauria (including Mixosauridae and Shastasauridae). The Fossil Hill Member in Nevada contains a clade of species that are closely related to one another.