Tony Wu / Ram's horn squid / Little post horn squid (Spirula spirula) internal shell with Pelagic goose barnacles (Lepas sp.). South Africa, Atlantic Ocean.

Paul D Stewart / Shell of extant deep water squid Spirula (Spirula spirula) backlit and sectioned to show how the structure of partitions within the shell is reminiscent of the extinct ammonites and living nautiloids.

Solvin Zankl / The Tail-Light Squid Shell (Spirula spirula) has a chambered, delicate shell, with diameter of about 1 cm from Raja Ampat, Indonesia. Digital focus stacking image

Solvin Zankl / Ram's horn squid (Spirula spirula) portrait. This species has an internal, chambered, endogastrically coiled shell in the shape of an open planispiral. The shell functions to control buoyancy. O...

Solvin Zankl / Ram's horn squid (Spirula spirula) portrait. This species has an internal, chambered, endogastrically coiled shell in the shape of an open planispiral. The shell functions to control buoyancy. O...

Solvin Zankl / Ram's horn squid (Spirula spirula) portrait. This species has an internal, chambered, endogastrically coiled shell in the shape of an open planispiral. The shell functions to control buoyancy. O...