Stylommatophora

Stylommatophora is an order of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs. 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.

Stylommatophora are known from the Cretaceous period up to the present day. A molecular clock estimate puts the origin of the crown group also to the Cretaceous.

2017 taxonomy 
The most up-to-date formal classification of Stylommatophora is that of Bouchet et al. (2017). Continuously updated information may be found at MolluscaBase. 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.

suborder Achatinina [“Achatinoid Clade”]

 superfamily Achatinoidea Swainson, 1840
 Achatinidae Swainson, 1840
 Aillyidae H. B. Baker, 1955
 Ferussaciidae Bourguignat, 1883
 Micractaeonidae Schileyko, 1999

 superfamily Streptaxoidea Gray, 1860
 Streptaxidae Gray, 1860
 Diapheridae Panha & Naggs, 2010

suborder Scolodontina

 superfamily Scolodontoidea H. B. Baker, 1925
 Scolodontidae H. B. Baker, 1925

suborder Helicina [“Non-Achatinoid Clade”]
incertae sedis
 superfamily Coelociontoidea Iredale, 1937
 Coelociontidae Iredale, 1937
 superfamily Papillodermatoidea Wiktor, Martin & Castillejo, 1990
 Papillodermatidae Wiktor, Martin & Castillejo, 1990
 superfamily Plectopyloidea Möllendorff, 1898
 Plectopylidae Möllendorff, 1898
 Corillidae Pilsbry, 1905
 Sculptariidae Degner, 1923
 superfamily Punctoidea Morse, 1864
 Punctidae Morse, 1864
 Charopidae Hutton, 1884
 Cystopeltidae Cockerell, 1891
 Discidae Thiele, 1931
 Endodontidae Pilsbry, 1895
 Helicodiscidae H. B. Baker, 1927
 Oreohelicidae Pilsbry, 1939
 superfamily Testacelloidea Gray, 1840
 Testacellidae Gray, 1840
 superfamily Urocoptoidea Pilsbry, 1898
 Urocoptidae Pilsbry, 1898
 Cerionidae Pilsbry, 1901
 Epirobiidae F. G. Thompson, 2012
 Eucalodiidae P. Fischer & Crosse, 1873
 Holospiridae Pilsbry, 1946
 infraorder Succineoidei [= Elasmognatha]
superfamily Succineoidea Beck, 1837
Succineidae Beck, 1837
superfamily Athoracophoroidea P. Fischer, 1883
Athoracophoridae P. Fischer, 1883
infraorder Rhytidoidei
superfamily Rhytidoidea Pilsbry, 1893
Rhytididae Pilsbry, 1893
Acavidae Pilsbry, 1895
Caryodidae Conolly, 1915
Clavatoridae Thiele, 1926
Dorcasiidae Connolly, 1915
Macrocyclidae Thiele, 1926
Megomphicidae H. B. Baker, 1930
Odontostomidae Pilsbry & Vanatta, 1898 (according to Salvador et al. 2023, in Bouchet et al. classified in Orthalicoidea) 
Strophocheilidae Pilsbry, 1902
infraorder Orthalicoidei
superfamily Orthalicoidea Martens, 1860
Orthalicidae Martens, 1860
Amphibulimidae P. Fischer, 1873
Bothriembryontidae Iredale, 1937
Bulimulidae Tryon, 1867
Cyclodontinidae Salvador & Breure, 2023 (see Salvador et al. 2023)
Megaspiridae Pilsbry, 1904
Simpulopsidae Schileyko, 1999
Tomogeridae Jousseaume, 1877 (see Salvador et al. 2023)
infraorder Pupilloidei [= Orthurethra]
superfamily Pupilloidea Turton, 1831
Pupillidae Turton, 1831
Achatinellidae Gulick, 1873
Agardhiellidae Harl & Páll-Gergely, 2017
Amastridae Pilsbry, 1910
Argnidae Hudec, 1965
Azecidae Watson, 1920
Cerastidae Wenz, 1923
Chondrinidae Steenberg, 1925
Cochlicopidae Pilsbry, 1900
Draparnaudiidae Solem, 1962
Enidae B. B. Woodward, 1903
Fauxulidae Harl & Páll-Gergely, 2017
Gastrocoptidae Pilsbry, 1918
Lauriidae Steenberg, 1925
Odontocycladidae Hausdorf, 1996
Orculidae Pilsbry, 1918
Pagodulinidae Pilsbry, 1924
Partulidae Pilsbry, 1900
Pleurodiscidae Wenz, 1923
Pyramidulidae Kennard & B. B. Woodward, 1914
Spelaeoconchidae A. J. Wagner, 1928 (Croatia, Bosnia and Hercegovina)
Spelaeodiscidae Steenberg, 1925
Strobilopsidae Wenz, 1915
Truncatellinidae Steenberg, 1925
Valloniidae Morse, 1864
Vertiginidae Fitzinger, 1833
infraorder Clausilioidei 
superfamily Clausilioidea Gray, 1855
Clausiliidae Gray, 1855
Pilsbrylia Hylton Scott, 1952 (South America; placement following Salvador et al. 2023)
infraorder Arionoidei
superfamily Arionoidea Gray, 1840
Arionidae Gray, 1840
Anadenidae Pilsbry, 1948
Ariolimacidae Pilsbry & Vanatta, 1898
Binneyidae Cockerell, 1891
Philomycidae Gray, 1847
infraorder Limacoidei [“Limacoid Clade”] 
superfamily Limacoidea Batsch, 1789
Limacidae Batsch, 1789
Agriolimacidae H. Wagner, 1935
Boettgerillidae Wiktor & I. M. Likharev, 1979
Vitrinidae Fitzinger, 1833
superfamily Gastrodontoidea Tryon, 1866
Gastrodontidae Tryon, 1866
Oxychilidae Hesse, 1927
Pristilomatidae Cockerell, 1891
superfamily Parmacelloidea P. Fischer, 1856
Parmacellidae P. Fischer, 1856
Milacidae Ellis, 1926
Trigonochlamydidae Hesse, 1882
superfamily Zonitoidea Mörch, 1864
Zonitidae Mörch, 1864
superfamily Trochomorphoidea Mörch, 1864
Trochomorphidae Möllendorff, 1890
Chronidae Thiele, 1931
Dyakiidae Gude & B. B. Woodward, 1921
Euconulidae H. B. Baker, 1928
Staffordiidae Thiele, 1931
superfamily Helicarionoidea Bourguignat, 1877
Helicarionidae Bourguignat, 1877
Ariophantidae Godwin-Austen, 1888
Urocyclidae Simroth, 1889
infraorder Oleacinoidei 
superfamily Oleacinoidea H. Adams & A. Adams, 1855
Oleacinidae H. Adams & A. Adams, 1855
Spiraxidae H. B. Baker, 1939
superfamily Haplotrematoidea H. B. Baker, 1925
Haplotrematidae H. B. Baker, 1925
infraorder Helicoidei [“Helicoid Clade”] 
superfamily Sagdoidea Pilsbry, 1895
Sagdidae Pilsbry, 1895
Solaropsidae H. Nordsieck, 1986
Zachrysiidae Robinson, Sei & Rosenberg, 2017
superfamily Helicoidea Rafinesque, 1815
Helicidae Rafinesque, 1815
Cepolidae Ihering, 1909
Labyrinthidae Borrero, Sei, Robinson & Rosenberg, 2017
 Thysanophoridae Pilsbry, 1926
 Camaenidae Pilsbry, 1895
 Polygyridae Pilsbry, 1895
 Helicidae Rafinesque, 1815  (western Palaearctic)
 Elonidae Gittenberger, 1977
 Trissexodontidae H. Nordsieck, 1987
 Helicodontidae Kobelt, 1904
 Sphincterochilidae Zilch, 1960
 Geomitridae C. Boettger, 1909
 Canariellidae Schileyko, 1991
 Hygromiidae Tryon, 1866
 Pleurodontidae Ihering, 1912
 Trichodiscinidae H. Nordsieck, 1987
 Xanthonychidae Strebel & Pfeffer, 1879

2005 taxonomy
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. 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.

clade Elasmognatha
 Superfamily Succineoidea
 Superfamily Athoracophoroidea

clade Orthurethra
 Superfamily Partuloidea
 Superfamily Achatinelloidea
 Superfamily Cochlicopoidea
 Superfamily Pupilloidea
 Superfamily Enoidea

informal group Sigmurethra
 Superfamily Clausilioidea
 Superfamily Orthalicoidea
 Superfamily Achatinoidea
 Superfamily Aillyoidea
 Superfamily Testacelloidea
 Superfamily Papillodermatoidea
 Superfamily Streptaxoidea
 Superfamily Rhytidoidea
 Superfamily Acavoidea
 Superfamily Punctoidea
 Superfamily Sagdoidea

"limacoid clade" (within the Sigmurethra)
 Superfamily Staffordioidea
 Superfamily Dyakioidea
 Superfamily Gastrodontoidea
 Superfamily Parmacelloidea
 Superfamily Zonitoidea
 Superfamily Helicarionoidea
 Superfamily Limacoidea

(not in limacoid clade, but is within the Sigmurethra)
 Superfamily Arionoidea
 Superfamily Helicoidea

Previous taxonomy
Subinfraorder Orthurethra
Superfamily Achatinelloidea Gulick, 1873
Superfamily Cochlicopoidea Pilsbry, 1900
Superfamily Partuloidea Pilsbry, 1900
Superfamily Pupilloidea Turton, 1831
Subinfraorder Sigmurethra
Superfamily Acavoidea Pilsbry, 1895
Superfamily Achatinoidea Swainson, 1840
Superfamily Aillyoidea Baker, 1960
Superfamily Arionoidea J.E. Gray in Turnton, 1840
Superfamily Buliminoidea Clessin, 1879
Superfamily Camaenoidea Pilsbry, 1895
Superfamily Clausilioidea Mörch, 1864
Superfamily Dyakioidea Gude & Woodward, 1921
Superfamily Gastrodontoidea Tryon, 1866
Superfamily Helicoidea Rafinesque, 1815
Superfamily Helixarionoidea Bourguignat, 1877 
Superfamily Limacoidea Rafinesque, 1815
Superfamily Oleacinoidea H. & A. Adams, 1855
Superfamily Orthalicoidea Albers-Martens, 1860 
Superfamily Plectopylidoidea Moellendorf, 1900
Superfamily Polygyroidea Pilsbry, 1894
Superfamily Punctoidea Morse, 1864
Superfamily Rhytidoidea Pilsbry, 1893
Superfamily Sagdidoidera Pilsbry, 1895
Superfamily Staffordioidea Thiele, 1931
Superfamily Streptaxoidea J.E. Gray, 1806
Superfamily Strophocheiloidea Thiele, 1926
Superfamily Trigonochlamydoidea Hese, 1882
Superfamily Zonitoidea Mörch, 1864

References

 
Extant Cretaceous first appearances