Stromboidea

Stromboideans have medium to large shells, attaining a wide variety of lengths depending on the species (20–400 mm[3] from the smallest aporrhaids to the largest strombids). A stromboidean shell has a medium (e.g. spider conchs, Lambis spp.) to high spire (e.g. tibias, Tibia spp.), and a thickened and frequently expanded outer lip (e.g. the queen conch, Lobatus gigas, or the goliath conch, Lobatus goliath) that may be ornamented by long spines (e.g. the spider conch, Lambis chiragra, common pelican foot, Aporrhais spp.) or digitations (e.g. the millipede spider conch, Lambis millepeda). The anterior portion of the outer lip may present a stromboid notch, an indentation through which one of the animal's long eyestalks may protrude.[3]

The shell morphology of some stromboideans (e.g. Lobatus gigas) is not solely determined by the animal's genes; environmental conditions such as location, diet, temperature and depth, and biological interactions such as predation, can greatly affect it.[4] Juvenile individuals of some species develop heavier shells when exposed to predators. They also develop wider and thicker shells with fewer but longer spines in deeper water.[5]

• 
  Five views of a shell of Aporrhais pespelecani, a species in the family Aporrhaidae
• 
  Five views of a shell of Lobatus gigas, a species in the family Strombidae
• 
  Struthiolaria papulosa, a species in the family Struthiolariidae
• 
  Five views of a shell of Tibia insulaechorab, a species in the family Rostellariidae

According to the classification proposed by Bouchet & Rocroi (2005),[9] the families and subfamilies in the superfamily Stromboidea are as follows. Fossil families are marked with a dagger †.

• Aporrhaidae Gray, 1850 - the pelican's foot shells, synonyms: Aporrhaididae, Aporrhaiidae,
  • Subfamily Aporrhainae Gray, 1850
  • Subfamily Arrhoginae Popenoe, 1983
  • † Subfamily Harpagodinae Pchelintsev, 1963
  • † Subfamily Perissopterinae Korotkov, 1992
  • † Subfamily Spinigerinae Korotkov, 1992 (inv.)
• † Colombellinidae P. Fischer, 1884
• † Pugnellidae Kiel & Bandel, 1999
• Seraphsidae Gray, 1853 - synonym: Terebellidae
• Strombidae Rafinesque, 1815 - the "true conchs"
• Struthiolariidae Gabb, 1868
• † Thersiteidae Savornin, 1915
• † Tylostomatidae Stoliczka, 1868

Some authors consider two following families as separate families:

• Rimellidae
• Rostellariidae - synonym: Tibiidae

Herbivory is the most common feeding habit among stromboideans. Snails in the family Strombidae were widely accepted as carnivores by several authors in the 19th century, a concept that persisted until the first half of the 20th century. This erroneous idea evidently originated in the writings of Jean-Baptiste Lamarck, who classified strombids with other supposedly carnivorous snails. This idea was subsequently repeated by other authors, but were not supported by observation.[12] Nowadays, strombids are known to be specialized herbivores and occasional detritivores. They are usually associated with shallow water reefs and seagrass meadows.[3]

Struthiolariids are ciliary mucous feeders, obtaining their nutrition from particles and organic matter suspended in the water. While remaining completely buried in the sand, struthiolariids are connected to the surface by two artificially produced holes. These holes are made by the animal's proboscis, held in place with mucus, and are used for inhalating and exhalating water. Feeding particles are captured as the inhaled water flows over the animal's gills, become embedded in mucus, and are moved along a ciliary tract that leads to the animal's mouth, where they are finally ingested.[3]