Knowra Nautilus Nautilus Nautilus is a genus of marine cephalopods whose members have an external coiled shell divided into gas-filled chambers. They are the only living cephalopods with an external chambered shell.
Nautilus shell : The external shell of a nautilus, coiled and partitioned into chambers by internal walls. Its chambered architecture lets the animal regulate buoyancy as it moves through the water column.
Cephalopod : A class of mollusks that includes octopuses, squids, cuttlefish, and nautiluses. Nautilus belongs to this group but retains an external shell unlike most living members.
Nautiloid : A member of Nautiloidea, a major lineage of externally shelled cephalopods. Living Nautilus is the sole surviving genus of a lineage with a deep fossil record.
Nautilus trapping : The capture of nautiluses using baited pots, often for shells or the aquarium trade. Harvest pressure from trapping has contributed to concern about declining populations.
Octopus : A soft-bodied cephalopod with eight arms and no external shell in living species. Octopuses exemplify the shell-less body plan that dominates living cephalopods.
Siphuncle : A tubular tissue strand that passes through the chambers of a nautilus shell. It controls chamber fluid and gas, enabling buoyancy adjustment.
Mollusca : A large animal phylum that includes snails, clams, chitons, and cephalopods. This broader lineage supplies the body plan shared by nautiluses and other mollusks.
Ammonoidea : An extinct subclass of externally shelled cephalopods that includes ammonites. Ammonoids were diverse shelled relatives, but their lineage disappeared at the end-Cretaceous extinction.
CITES : An international agreement regulating trade in wild animals and plants. Nautilus species entered CITES Appendix II in 2017, restricting international trade.
Squid : A fast-swimming cephalopod with an elongated body, fins, and usually an internal shell. Squids retain a reduced internal shell rather than Nautilus's external chambered one.
Show all 26