Stylommatophora is an
order[3] of air-breathing
land snails and
slugs,
terrestrialpulmonategastropodmolluscs. This taxon includes most land snails and
slugs. Stylommatophorans lack an
operculum, but some close their shell apertures with temporary "operculum" (
epiphragm) made of calcified mucus. They have two pairs of retractile tentacles, the upper pair of which bears
eyes on the tentacle tips. All stylommatophorans are
hermaphrodites.
The two strong
synapomorphies of Stylommatophora are a long pedal gland placed beneath a membrane and two pairs of retractile tentacles.[4]
Stylommatophora are known from the
Cretaceous period up to the present day.[5] A molecular clock estimate puts the origin of the crown group also to the Cretaceous.[6]
2017 taxonomy
The most up-to-date formal classification of Stylommatophora is that of Bouchet et al. (2017).[3] Continuously updated information may be found at
MolluscaBase.[7] The 2017 system already becomes obsolete in some parts due to new phylogenetic studies.
Rhytidoidea is apparently not a monophyletic group, but rather a collection of lineages from the southern hemisphere with unresolved relationships.[8]
According to the
taxonomy of the Gastropoda by Bouchet & Rocroi (2005) based on evolutionary ancestry, Stylommatophora is a clade in the clade
Eupulmonata within informal group
Pulmonata.[9] It uses unranked clades for taxa above the rank of superfamily (replacing the ranks suborder, order, superorder and subclass) and the traditional
Linnaean approach for all taxa below the rank of superfamily.
The
clade Stylommatophora contains the subclades Elasmognatha, Orthurethra and the informal group Sigmurethra. The term "informal group" has been used to indicate whenever
monophyly has not been tested, or where a traditional taxon of gastropods has now been discovered to be
paraphyletic or
polyphyletic.
^Solem A. (1978). Classification of the land Mollusca. In: Fretter V. & Peake J. (eds). Pulmonates, Vol. 2A. London, Academic Press, 49–97.
^Sutcharit C., Naggs F., Wade C. M., Fontanilla I. & Panha S. (2010). "The new family Diapheridae, a new species of Diaphera Albers from Thailand, and the position of the Diapheridae within a molecular phylogeny of the Streptaxoidea (Pulmonata: Stylommatophora)". Zoological Journal of the Linnean Society160: 1-16.
doi:
10.1111/j.1096-3642.2009.00598.x.