Systellommatophora Explained

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.

Anatomy

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]

Taxonomy

According to the previous taxonomy of the Gastropoda (Ponder & Lindberg, 1997) Systellommatophora was considered to be a suborder or an order.

The following two superfamilies and families have been recognized in the taxonomy of Bouchet & Rocroi (2005):

• superfamily Onchidioidea Rafinesque, 1815
  • Onchidiidae Rafinesque, 1815
• Superfamily Veronicelloidea Gray, 1840
  • Veronicellidae Gray, 1840
  • Rathouisiidae Heude, 1885

Notes and References

1. MolluscaBase eds. (2020). MolluscaBase. Stylommatophora. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=447 on 2020-05-02
2. Dayrat B.. 2009. Review of the current knowledge of the systematics of Onchidiidae (Mollusca: Gastropoda: Pulmonata) with a checklist of nominal species. Zootaxa. 2068. 1–26. 10.11646/zootaxa.2068.1.1 . preview.
3. Valiguna flava (Heynemann, 1885) from Indonesia and Malaysia: Redescription and Comparison with Valiguna siamensis (Martens, 1867) (Gastropoda: Soleolifera: Veronicellidae) . Schilthuizen M. . Thome J. W. . Veliger . 50 . 3 . 163–170 . 2008.
4. Book: Barnes, Robert D. . 1982 . Invertebrate Zoology . Holt-Saunders International . Philadelphia, PA. 377. 0-03-056747-5.
5. A new mountain Platevindex from Philippine Islands (Pulmonata: Onchidiidae) . TILLIER, S . Journal of Molluscan Studies . 49 . supp12A . 198 . 1983 . Malacological Soc London.
6. Book: The Marine Flora and Fauna of Hong Kong and Southern China III___ Fouling and pollution, morphology, behaviour and physiology, Hoi Ha Wan . Hong Kong University Press . 978-962-209-295-2 . Morton, Brian . 1992.
7. 10.1046/j.1096-3642.2002.00018.x . Evolutionary relationships of euthyneuran gastropods (Mollusca): a cladistic re-evaluation of morphological characters . 2002 . Dayrat . B. . Tillier . S. . Zoological Journal of the Linnean Society . 135 . 4 . 403. free .