We place three families in the sepioid clade: Sepiidae, Sepiadariidae and Sepiolidae. The latter two families are related and placed in the suborder Sepiolida. Two additional families (Idiosepiidae, Spirulidae) have often been included in the Order Sepioidea. However considerable uncertainty exists concerning the relationships of the Idiospiidae in general and the closeness of the relationship of the Spirulidae to the sepioid families. Members of the sepioidea are mostly neritic and upper slope benthic species although one group (Heteroteuthinae) is pelagic.

Brief diagnosis:

A decapodiform ...

• with corneal membranes covering eye lenses.
• without branchial canals in gills.
• with circularis muscles in suckers.