Which is the other name for paper nautiluses?
The argonauts (genus 'Argonauta', the only extant genus in the family 'Argonautidae') are a group of pelagic octopuses. They are also called paper nautiluses, referring to the paper-thin eggcase that females secrete. This structure lacks the gas-filled chambers present in chambered nautilus shells and is not a true cephalopod shell, but rather an evolutionary innovation unique to the genus 'Argonauta'. It is used as a brood chamber and for trapped surface air to maintain buoyancy.
Argonauts are found in tropical and subtropical waters worldwide; they live in the open ocean, i.e. they are pelagic. Like most octopuses, they have a rounded body, eight arms and no fins. However, unlike most octopuses, argonauts live close to the sea surface rather than on the seabed.