A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.
The nautilus is an ancient pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.
Nautilus is a genus of cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of morphology from those placed in the sister taxon Allonautilus. The oldest fossils of the genus are known from the Late Eocene Hoko River Formation, in Washington State and from Late-Eocene to Early Oligocene sediments in Kazakhstan. The oldest fossils of the modern species Nautilus pompilius are from Early Pleistocene sediments off the coast of Luzon in the Philippines.
The genus Allonautilus contains two species of nautiluses, which have a significantly different morphology from those placed in the sister taxon Nautilus. Allonautilus is now thought to be a descendant of Nautilus, rendering the latter genus paraphyletic.
Nautilus stenomphalus, also known as the white-patch nautilus, is a species of nautilus native to the Great Barrier Reef. N. stenomphalus is very similar to N. pompilius and may in fact represent a subspecies. It is separated by the absence of a thickened callus and the presence of white patches in the umbilical and shoulder regions of the shell. The sheaths of this species have scalloped edges compared with the smooth sheaths of N. pompilius. N. stenomphalus also differs slightly in hood ornamentation. The shell is usually up to around 180 mm in diameter, although the largest specimen ever recorded measured 201 mm.
Allonautilus scrobiculatus, also known as the crusty nautilus or fuzzy nautilus, is a species of nautilus native to the waters around New Guinea, specifically New Britain and Milne Bay, and the Solomon Islands. A. scrobiculatus is recognizable by the large open umbilicus, which is around 20% of the shell diameter at its widest point. This species, along with the closely related A. perforatus, were originally placed in the genus Nautilus, but have recently been given their own genus on account of significant morphological differences. The most obvious are features of the shell, including crease and an encrusting layer (periostracum) that covers most of the shell. Gills and reproductive structures also differ significantly from members of the genus Nautilus. The shell is usually up to around 18 cm in diameter, although the largest specimen ever recorded measured 21.5 cm. The species was thought to have gone extinct after 1986, but was rediscovered in July 2015.
Sepia adami is a species of cuttlefish native to the southwestern Indian Ocean. It is known only from the type locality, S 79ºE off Cape Natal. It lives at a depth of up to 99 m.
Sepia bartletti is a species of cuttlefish native to the western Pacific Ocean. It is known only from the type locality. Depth range is unknown. Some authorities regard S. bartletti as a nomen dubium.
Sepia baxteri is a species of cuttlefish native to the southwestern Pacific Ocean, specifically the waters around Lord Howe Island. It is known only from the type cuttlebones. Depth range is unknown.
Sepia joubini is a species of cuttlefish native to the southwestern Indian Ocean, specifically South Africa, off Tugela River Mouth, to Cape Natal, off southern Mozambique, and in the Saya-de-Malha Bank. It lives at a depth of between 66 and 170 m.
Rossia glaucopis is a species of bobtail squid native to the southeastern Pacific Ocean, specifically the waters around Chile.
Austrorossia mastigophora is a species of bobtail squid native to western, southern and eastern Africa, from Guinea and Somalia to the Cape of Good Hope. A doubtful record of this species exists from Chile. It lives at depths to approximately 640 m.
Sepia robsoni is a species of cuttlefish known only from its type locality, Hout Bay in South Africa. It lives at depths of between 17 and 37 m.
Sepiella cyanea is a species of cuttlefish native to the southwestern Indian Ocean, from Port Elizabeth and Durban north to central Mozambique (26ºN) and Madagascar. It lives at depths of 13 to 73 m.
Sepiella ocellata is a species of cuttlefish known only from the type locality off Java. The depth range of this species is unknown. Only a single male specimen has been recorded. The status of S. ocellata is questionable.
Euprymna hoylei is a species of bobtail squid native to the tropical waters of the Indo-Pacific, specifically the western Pacific Ocean and northwestern Australia. Little is known about the size range of this species.
Sepietta petersi, also known as the mysterious bobtail, is a species of bobtail squid native to the Mediterranean Sea. A doubtful record of S. petersi also exists from the Atlantic Ocean off Morocco.
Inioteuthis japonica is a species of bobtail squid native to the western Pacific Ocean, specifically the waters off China, Taiwan, and southern Japan.
Rossia pacifica diegensis is a subspecies of bobtail squid native to the eastern Pacific Ocean off Santa Catalina Basin, California. It occurs at greater depths than its sister taxon R. p. pacifica.
Inioteuthis is a genus of bobtail squid comprising three species.
