Cephalopod zootomy

thumb|upright=1.7|Chromatophores in the skin of a squid Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, have a class of cells called melanocytes for coloration.

The radula (; : radulae or radulas) is an anatomical structure found in most mollusks, serving as their primary feeding tool. Often compared to a tongue, this minutely toothed, chitinous ribbon typically functions by scraping or cutting food before it enters the esophagus. Mollusks in every class possess a radula, except for bivalves, which instead employ waving cilia to draw in minute organisms for feeding.

thumb|300px|right|The elongate jewel squid (Histioteuthis reversa), so called because the photophores festooning its body make it appear bejewelled. thumb|300px|right|Diagram of a cephalopod's photophore, in vertical section.

part of the anatomy of molluscs

thumb|Cuttlebone of Sepia officinalis (left to right: ventral, dorsal, and lateral views). The cuttlebone is about 15cm in length. thumb| thumb|Tortoise with cuttlebone thumb|Fossil cuttlebone of the Pliocene species [[Sepia rugulosa]] thumb|Fossilised cuttlebone-like gladius (cephalopod)|gladius of [[Trachyteuthis]]

exoskeleton of an animal in the phylum Mollusca

anatomical structure which is part of the body of some aquatic molluscs

thumb|160px|Georges Cuvier's original illustration of an octopus hectocotylus. Mistaking it for its own separate organism, he named it Hectocotyle octopodis.

Organ in cephalopods used to squirt ink in defense

right|thumb|upright=2.5|A diagram of a hypothetical ancestral mollusc (HAM) with osphradia indicated on the far right side of the image inside the posterior mantle cavity The osphradium is a pigmented chemosensory epithelium patch in the mantle cavity present in six of the eight extant classes of molluscs (it is absent in the Scaphopoda and Monoplacophora; most Cephalopoda also lack it, but the nautilus has what appears to be a set of osphradia), on or adjacent to the ctenidia (gills). The main function of this organ is disputed but it is believed to be used to test incoming water for silt and

respiratory organ or gill which is found in many mollusks

very large nerve fiber that controls part of the water jet propulsion system in squid

thumb|upright 2.0|Some examples of aptychi (top right: Oppelia from Late Jurassic of Solnhofen, Germany; bottom left: aptychi (recto and versus) from Late Jurassic of Lombardy, Italy), and conceptual scheme of their function if indeed they were used to close the shell aperture, as opposed to being jaws. thumb|One of what would have been a pair of aptychi (at first given the name Trigonellites|Trigonellites latus and described as a bivalve) from the [[Kimmeridge Clay Formation in England]]

body part of cephalopods

distal portion of the fore limb of an animal

Visual sensory organs of cephalopod mollusks

limbs of cephalopod molluscs

thumb|300px|Fossilised Orthoceras orthocones. An orthocone is the long, cone-shaped shell belonging to several species of ancient nautiloid cephalopod—the prehistoric ancestors of today's marine cephalopod mollusks, including the cuttlefishes, nautiluses, octopuses and squids. During the 18th and 19th centuries, all such shells discovered were given the "catch-all" name Orthoceras, thus creating a wastebasket taxon. However, it is now known that many species, genera and families of nautiloids developed or retained this form of shell.

thumb|Cutaway of a nautilus shell showing the chambers