Seguenzioidea

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

==Description== thumb|Three Seguenziid gastropods 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.