The name "octopus" comes from the Greek. It means eight-foot, and that also makes an octopus special among other cephalopods. Where a squid or a cuttlefish has got ten arms, an octopus has got eight. In that regards, octopuses have something in common with their nearest relatives, the argonauts, which also have got eight arms.
The number of their arms is not the only thing, which separates octopuses from other cephalopods. It is also the absence of a shell. All cephalopods, leaving aside the ancient Nautilus, which still has got an external shell, have got the tendency to reduce their shell, so squids only have left an internal sword-shaped structure called the gladius and cuttlefish have their internal cuttlebone, also a remainder of a shell. Octopuses have got neither, they lack any trace of a shell, internal or external.
The name "octopus" comes from the Greek. It means eight-foot, and that also makes an octopus special among other cephalopods. Where a squid or a cuttlefish has got ten arms, an octopus has got eight. In that regards, octopuses have something in common with their nearest relatives, the argonauts, which also have got eight arms.The number of their arms is not the only thing, which separates octopuses from other cephalopods. It is also the absence of a shell. All cephalopods, leaving aside the ancient Nautilus, which still has got an external shell, have got the tendency to reduce their shell, so squids only have left an internal sword-shaped structure called the gladius and cuttlefish have their internal cuttlebone, also a remainder of a shell. Octopuses have got neither, they lack any trace of a shell, internal or external.
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