Palau nautilus (Nautilus belauensis)
Nautilus belauensis, also known as the Palau nautilus, is a species of nautilus native to the waters around the Pacific island nation of Palau. Nautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera. The nautilus is similar in general form to other cephalopods, with a prominent head and tentacles. Nautiluses typically have more tentacles than other cephalopods, up to ninety. These tentacles are arranged into two circles and, unlike the tentacles of other cephalopods, they have no suckers, are undifferentiated and retractable. The radula (structure used for feeding) is wide and distinctively has nine teeth. There are two pairs of gills. Nautiluses are the sole living cephalopods whose bony body structure is externalized as a shell. The animal can withdraw completely into its shell and close the opening with a leathery hood formed from two specially-folded tentacles.