nautiluses is the only cephalopod with an exoskeleton. all shells of mollusks are formed from the ectoderm which is outer layer of the embryo. The largest group of shelled cephalopods, the ammonites, are extinct. The carbonate mineralilized shell has to do with the shell's matrix having an acid matrix, while the gladius of squid contains a basic matrix.
The inward movement of an outer layer of the ectoderm forms during the embryonic period, resulting in a shell that is an internal skeleton in adults. The same is true of the gladius of squid and octopus. octopus have cartilage in their fin that supports the fin, which are sometimes called a "shell vestige" or "gladius". They have no trace of an internal shell, and some squids also do not have a gladius.
The Spiral shell begins as an organic structure, and is then turned into a mineral like structure after a short period of time. Females of the octopus genus Argonauta secrete a thin egg case in which their eggs ARE HELD, and this is USUALLY KNOWN as a "shell", although it is not attached to the body of the animal iT iS STill regarded as a shell of the octopus.
The inward movement of an outer layer of the ectoderm forms during the embryonic period, resulting in a shell that is an internal skeleton in adults. The same is true of the gladius of squid and octopus. octopus have cartilage in their fin that supports the fin, which are sometimes called a "shell vestige" or "gladius". They have no trace of an internal shell, and some squids also do not have a gladius.
The Spiral shell begins as an organic structure, and is then turned into a mineral like structure after a short period of time. Females of the octopus genus Argonauta secrete a thin egg case in which their eggs ARE HELD, and this is USUALLY KNOWN as a "shell", although it is not attached to the body of the animal iT iS STill regarded as a shell of the octopus.