The Systellommatophora (synonym Gymnomorpha) is a clade of primitive, air-breathing slugs, according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005). [1]

Land slug Laevicaulis alte (Veronicelloidea)
Sea slug Onchidella sp. (Onchidioidea)
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Superorder: Eupulmonata
Order: Systellommatophora

See text



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):


  1. ^ MolluscaBase eds. (2020). MolluscaBase. Stylommatophora. Accessed through: World Register of Marine Species at: on 2020-05-02
  2. ^ a b Dayrat B. (2009). "Review of the current knowledge of the systematics of Onchidiidae (Mollusca: Gastropoda: Pulmonata) with a checklist of nominal species" (preview). Zootaxa. 2068: 1–26.
  3. ^ a b Schilthuizen M.; Thome J. W. (2008). "Valiguna flava (Heynemann, 1885) from Indonesia and Malaysia: Redescription and Comparison with Valiguna siamensis (Martens, 1867) (Gastropoda: Soleolifera: Veronicellidae)". Veliger. 50 (3): 163–170.
  4. ^ Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 377. ISBN 0-03-056747-5.
  5. ^ TILLIER, S (1983). "A new mountain Platevindex from Philippine Islands (Pulmonata: Onchidiidae)". Journal of Molluscan Studies. Malacological Soc London. 49 (supp12A): 198.
  6. ^ Morton, Brian (1992). The Marine Flora and Fauna of Hong Kong and Southern China III___ Fouling and pollution, morphology, behavious and physiology, Hoi Ha Wan. Hong Kong University Press. ISBN 978-962-209-295-2.
  7. ^ Dayrat, B.; Tillier, S. (2002). "Evolutionary relationships of euthyneuran gastropods (Mollusca): a cladistic re-evaluation of morphological characters". Zoological Journal of the Linnean Society. 135 (4): 403. doi:10.1046/j.1096-3642.2002.00018.x.
  8. ^ "Systellommatophora". Integrated Taxonomic Information System.