Nautilus

Nautilus
Chambered nautilus: Nautilus pompilius
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Nautilida
Family:	Nautilidae Blainville, 1825
Genera
Allonautilus Nautilus

Nautilus^[1] is the common name for cephalopods of the family Nautilidae. They are the only living members of the subclass Nautiloidea.^[2] In appearance, they have not changed much in millions of years. The term chambered nautilus is also used for any species of the Nautilidae.

Many biologists see them as 'living fossils', because they are the only living descendents of the group which gave rise to the ammonites in the Palaeozoic era.

Today, there are six living species in two genera. The species Nautilus pompilius, from Western Australia is the largest and best known. It get up to 27 cm in diameter. However, most other nautiluses never exceed 20 cm. The Bellybutton nautilus, Nautilus macromphalus, is the smallest species, usually measuring only 16 cm.

The radula is wide and has exactly nine teeth. There are two pairs of gills.

1. ↑ from Greek nautilos, 'sailor'
2. ↑ Sweeney M.J. 2002. Taxa associated with the Family Nautilidae Blainville, 1825. Archived 2007-09-30 at the Wayback Machine Tree of Life web project.