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Gastropteridae Family

Family Gastropteridae

In these small cephalaspideans, sometimes commonly known as bat-winged slugs, the head shield is short and triangular. Anteriorly the head shield is raised and folded into a long medial inhalant siphon that arches forward over the head and is sometimes (in the genus Siphopteron) supported by a medial rib which may extend past the siphon itself.
The posterior shield overlaying the visceral hump is large and elongate. On the dorsum there is a right lateral ridge that may continue diagonally and posteriorly to form a prominent short papilla or a longer filament (or two filaments). The shell is reduced, internal or absent.
The broad foot is somewhat longer than the visceral hump and evolves laterally into large, thin parapodia which meet or overlap on the dorsum. The plicate gill may be observed between the body and the right parapodium especially in the genus Sagaminopteron where it is quite large, extending past the visceral hump posteriorly.
Many species can swim when disturbed by flapping their large parapodia. Striking colours, combinations of colours, and or patterns are exhibited by the majority of gastropterids.
Many gastropterids are found living on certain sponges and it seems likely these sponges may constitute their diet.