Interesting innovations (House 1988)
1). A chambered shell with siphuncle which is a slender outgrowth of the body wall which secretes gas into the chambered shell for buoyancy is present in most cephalopods.
2). Refinement of the siphuncle which allows both poise and hydrostatic control of buoyancy.
3). Some groups such as the Nautiloidea have a simple siphuncle, but they have a wide range of shell forms.
4). A mechanism for protected fertilization leading to the formation of an egg for the developing embryo, rather than a ciliated larval stage, as in other molluscs.
5). The achievement of mantle pump respiration allowed the exhalent current to be used for the jet propulsion system of locomotion. The ability to contract the mantle wall allowed for greater force and speed.
6). Skin camouflage is possible because of chromatophores in the skin.
7). In more advanced cephalopods
such as the squid and octopus the eye
is comparable to that of vertebrates.