Spirula

Spirula Temporal range: Miocene–Recent[1] PreꞒ Ꞓ O S D C P T J K Pg N
Dorsal view of female
Ventral view of female (chromatophores of mantle missing)
Conservation status
Least Concern  (IUCN 3.1)[2]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Spirulida
Family:	Spirulidae Owen, 1836
Genus:	Spirula Lamarck, 1799
Species:	S. spirula
Binomial name
Spirula spirula (Linnaeus, 1758)
Synonyms
Nautilus spirula Linnaeus, 1758

Spirula spirula is a species of deep-water squid-like cephalopod mollusk. It is the only extant member of the genus Spirula, the family Spirulidae, and the order Spirulida. Because of the shape of its internal shell, it is commonly known as the ram's horn squid^[3] or the little post horn squid. Because the live animal has a light-emitting organ, it is also sometimes known as the tail-light squid.

Live specimens of this cephalopod are very rarely seen because it is a deep-ocean dweller. The small internal shell of the species is, however, quite a familiar object to many beachcombers. The shell of Spirula is extremely light in weight, very buoyant, and surprisingly durable; it very commonly floats ashore onto tropical beaches (and sometimes even temperate beaches) all over the world. This seashell is known to shell collectors as the ram's horn shell or simply as Spirula.