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Pteropod | Sea Snails, Shells & Swimming | Britannica
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pteropod A shell-less sea snail (Cliona limacina). sea butterfly
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Sea otter (Enhydra lutris), also called great sea otter, rare, completely marine otter of the northern Pacific, usually found in kelp beds. Floats on back. Looks like sea otter laughing. saltwater otters
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pteropod
pteropod A pteropod.

pteropod

mollusk
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Also known as: sea butterfly
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Also called:
sea butterfly

pteropod, small marine gastropods of the subclass Opisthobranchia (phylum Mollusca) characterized by a foot modified to form a pair of winglike flaps (parapodia) that are used for swimming. They live at or near the sea surface; most are less than 1 cm (0.4 inch) long.

A shell-less sea snail (Cliona limacina).
A shell-less sea snail (Cliona limacina).

Those that lack a shell and have complicated mechanisms for capturing and eating other small animals constitute the order Gymnosomata; those having a shell and feeding by means of cilia and mucus constitute the order Thecosomata. The shell is delicate and translucent; contrasting forms are seen in the straight-needle pteropod (Creseis acicula), the coiled pteropod (Limacina species), and the long-snouted pteropod (Cavolina longirostris).

This article was most recently revised and updated by John P. Rafferty.