Acteonoidea
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Acteonoidea is a superfamily of headshield slugs or snails, marine gastropod mollusks belonging to the suborder Cephalaspidea, the headshield slugs and snails. They are considered to be very primitive opisthobranchs.
In the new taxonomy of Bouchet & Rocroi (2005), The superfamily Acteonoidea has been included into the new Informal Group "Lower Heterobranchia" (Heterostropha sensu Ponder & Warén, 1988).
The shell of these micromollusks is gradually reduced in size relative to the size of the body from the Acteonidae, to the Bullidae, to the Hydatinidae.
They all have first an external penis; afterwards they develop the female part (a process called protrandry). They are distinguished from other opisthobranchs, by having a headshield, lack of tentacles and broad parapodia (mantle flaps), which fold along the side of the shell as the mollusk crawls on a sandy bottom. They are carnivores, preying on polychaete worms.
[edit] Families in the superfamily Acteonoidea
- family Acteonidae d' Orbigny, 1843
- family Bullinidae Gray, 1850
- family Aplustridae Gray, 1847 (former name Hydatinidae has been declared invalid)
- † family Acteonellidae Gill, 1871
- † family Zardinellidae Bandel, 1994
