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These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles ( muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods " inkfish ", referring to their common ability to squirt ink.
Approximately half of its shell was filled with septa; 7 were recorded in a 2 cm shell. [13] Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side. [5] Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods, [5] and the Plectronocerida have ...
Nautilus. The nautilus (from Latin nautilus ' paper nautilus ', from Ancient Greek ναυτίλος nautílos 'little sailor') [ 3] is an ancient pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina . It comprises nine living species in two ...
Octopus. An octopus ( pl.: octopuses or octopodes[ a]) is a soft-bodied, eight-limbed mollusc of the order Octopoda ( / ɒkˈtɒpədə /, ok-TOP-ə-də[ 3] ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric ...
Cuttlefish, like other cephalopods, have sophisticated eyes. The organogenesis and the final structure of the cephalopod eye fundamentally differ from those of vertebrates such as humans. [20] Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution. The cuttlefish pupil is a smoothly ...
Siphuncle. A cross-section through a Nautilus shell, showing a narrow siphuncle connecting the chambers of the shell. The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living ...
Cephalopod limb. Arms and buccal mass of the squid Taningia danae. As in other Octopoteuthidae, the tentacles are absent in adults. All cephalopods possess flexible limbs extending from their heads and surrounding their beaks. These appendages, which function as muscular hydrostats, have been variously termed arms, legs or tentacles.
The chambered nautilus ( Nautilus pompilius ), also called the pearly nautilus, is the best-known species of nautilus. The shell, when cut away, reveals a lining of lustrous nacre and displays a nearly perfect equiangular spiral, although it is not a golden spiral. The shell exhibits countershading, being light on the bottom and dark on top.