The Systellommatophora (synonym Gymnomorpha) is a clade of primitive, air-breathing slugs, according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005). [1]
They are marine and terrestrial pulmonate gastropods within the Heterobranchia. There are two superfamilies in this clade. Slugs in the superfamily Onchidioidea are primarily marine (except for five land-dwelling or freshwater species),[2] whereas slugs in the superfamily Veronicelloidea are primarily terrestrial.
No species in this clade have shells as adults.[2][3] These slugs are distinguished by the location of the anus at the rear of the body.[4]
Although neither superfamily bears shells as adults,[3] the Onchidioidea do possess a vestigial, non-mineralized shell sac[5] and possess a larval shell.[6] It is not known whether or not the veronicellids bear a larval shell.[7]
According to the previous taxonomy of the Gastropoda (Ponder & Lindberg, 1997) Systellommatophora was considered to be a suborder or an order.[8]
The following two superfamilies and families have been recognized in the taxonomy of Bouchet & Rocroi (2005):
The Systellommatophora (synonym Gymnomorpha) is a clade of primitive, air-breathing slugs, according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005).
They are marine and terrestrial pulmonate gastropods within the Heterobranchia. There are two superfamilies in this clade. Slugs in the superfamily Onchidioidea are primarily marine (except for five land-dwelling or freshwater species), whereas slugs in the superfamily Veronicelloidea are primarily terrestrial.
