Sunellidae was originally made to include three genera: Sunella, Chiella &and Luella but later the latter two where synonymized with Sunella. Later two other genera, Jinningella &and Combinivalvula were described and the definition of Sunellidae was strictened by adding the additional defining feature, the possession of an anterodorsal sulcus. In 2021 one species of Sunella, S. bispinata was moved to the genus Caudicaella. It was assigned to Isoxyida in 2025.
Usually the soft anatomy of sunellids is not preserved but a few examples of soft part preservation have been recorded in Combinivalvula ''chenjiangensis and Sunella cf. shensiella''.