(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 determined to be at the very beginning of Ichthyosauria, separate from more advanced members of Hueneosauria (including Mixosauridae and Shastasauridae). A study on C. duelferi found that all species from the Fossil Hill Member in Nevada belong to a single group.