Acteonoidea

Acteonoidea
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Orthogastropoda
Superorder:	Heterobranchia
Order:	Opisthobranchia
Suborder:	Cephalaspidea
Superfamily:	Acteonoidea d'Orbigny, 1843
Families
Acteonidae Bullinidae Hydatinidae

The superfamily of headshield slugs of the Acteonoidea belongs to the suborder Cephalaspidea and the Opisthobranchia.

They are considered very primitive opisthobranchs. The shell of these micromollusks is gradually reduced in consecutive order from Acteonidae, to Bullidae, to 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.

Taxonomy

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

Further treatment at Cephalaspidea