Sea butterfly

Sea butterflies
Temporal range:
Limacina helicina
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Clade: Euopisthobranchia
Order: Pteropoda
Suborder: Thecosomata
Blainville, 1824
Families

Limacinidae
Cavoliniidae
Cliidae
Creseidae
Cuvierinidae
Praecuvierinidae
Peraclididae
Cymbuliidae
Desmopteridae

The Thecosomata (collective/plural: thecosomes, meaning "case/shell-body"), or sea butterflies, are a taxonomic suborder of small, pelagic, free-swimming sea snails known as holoplanktonic opisthobranch gastropod mollusks, in the order Pteropoda (also included within the informal group Opisthobranchia). Most pteropods have some form of calcified shell, although it is often very light, even translucent.

The sea butterflies include some of the world's most abundant gastropod species; as their large numbers are an essential part of the ocean food chain, they are a significant contributor to the oceanic carbon cycle.