[2] According to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), as well as the Cycloneritida, the subclass Neritimorpha also contains the (entirely fossil) clade Cyrtoneritimorpha, plus a number of other fossil families that are currently unassigned.

The earliest evolutionary forms of Cycloneritimorpha show double visceral organs, double gills, and normally a double-chambered heart.

[3] The taxonomy of Cycloneritida is based on work by Kano et al. (2002)[4] that recognizes 4 clades.

These clades are established on genetic analysis (28S rRNA) of recent species only.

These clades proposed by Kano are ranked as superfamilies in the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005).