Seguenzioidea
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Seguenzioidea is a superfamily of sea snails, marine gastropod mollusks in the clade Vetigastropoda.
Description

The distinctive characteristics of the shells of the Seguenzioidea are:
- the nacreous layer (a plesiomorphic character, i.e. a character state that a taxon is inferred to have been retained from its ancestors) This occurs also in the following families: Pleurotomariidae, Haliotidae, Turbinidae, Trochidae, and possibly in the Skeneidae.
- the protoconch has a trochoid shape.
- usually with one or more labral sinuses. This character is also found is several other superfamilies such as Neomphaloidea, Pleurotomarioidea, Fissurelloidea, and Scissurelloidea and in the families Siliquariidae and Turridae. Therefore, this characteristic is to be considered autapomorphic.
- a unique radular formula with an underlying rhipidoglossate ground plan.
Taxonomy
Seguenzioidea was placed in part or in whole previously to 1979 either in the Archaeogastropoda near the superfamily Trochoidea or in the Caenogastropoda near the superfamily Stromboidea. In 1987 Salvini-Plawén and Haszprunar changed its status to the suborder Seguenziina, based on the radular formula that they considered to be intermediate between "rhipidoglossate" and "taenioglossate". At about the same time in 1987 Goryachev elevated the superfamily to ordinal status Seguenziiformes in the superorder Littorinimorpha, based on the taenioglossal radula.
2005 taxonomy
2005 taxonomy according to Bouchet & Rocroi, 2005. (Families that are exclusively fossil are indicated with a dagger †.)
Superfamily Seguenzioidea Family Seguenziidae Family Chilodontaidae † Family Eucyclidae † Family Laubellidae
2007–2009 taxonomy
Kano et al. (2009) elevated the subfamily Calliotropinae to the family level as the Calliotropidae, and the subfamily Cataeginae to family level as the Cataegidae.
The superfamily Seguenzioidea consists of six families:
- Cataegidae McLean & Quinn, 1987
- Chilodontaidae Wenz, 1938
- Choristellidae Bouchet & Warén, 1979
- Eucyclidae Koken, 1896
- † Eucycloscalidae Gründel, 2007
- Eudaroniidae Gründel, 2004
- † Eunemopsidae Bandel, 2010
- † Lanascalidae Bandel, 1992
- † Laubellidae Cox, 1960
- Pendromidae Warén, 1991
- † Pseudoturcicidae Bandel, 2010
- † Sabrinellidae Bandel, 2010
- Seguenziidae Verrill, 1884
- Trochaclididae Thiele, 1928
Unassigned to a family
- Adeuomphalus Seguenza, 1876 Aequispirella Finlay, 1924 Akritogyra Warén, 1992 Anekes Bouchet & Warén, 1979 Benthobrookula A. H. Clarke, 1961 Brookula Iredale, 1912 Eudaronia Cotton, 1945 Granigyra Dall, 1889 Lissotesta Iredale, 1915 Lissotestella Powell, 1946 Microcarina Laseron, 1954 Moelleriopsis Bush, 1897 Notosetia Iredale, 1915 Palazzia Warén, 1991 Putilla A. Adams, 1867 Retigyra Warén, 1989 Trenchia Knudsen, 1964 Ventsia Warén & Bouchet, 1993 Vetulonia Dall, 1913 Wanganella Laseron, 1954 Xyloskenea B. A. Marshall, 1988
Unassigned genera brought into synonymy
- Abyssogyra A.H. Clarke, 1961: synonym of Moelleriopsis Bush, 1897
- Intortia Egorova, 1972: synonym of Lissotesta Iredale, 1915
- Molleriopsis : synonym of Moelleriopsis Bush, 1897
- Kano, Y. 2008: Vetigastropod phylogeny and a new concept of Seguenzioidea: Independent evolution of copulatory organs in the deep-sea habitats. Zoologica Scripta 37: 1-21
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