Limacina rangii is a species of swimming sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies (Thecosomata). Limacina rangii is a keystone species of the mesozooplankton of Antarctic pelagic ecosystems.(Main article: Limacina helicina § Subspecies) Until 2010 this taxon was known only as Limacina helicina antarctica or as Limacina helicina f. antarctica. Limacina rangii is however now considered to be a separate species from Limacina helicina, based on cytochrome c oxidase subunit I (COI) gene sequences.