The nautilus is a 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.
The Argonautidae are a family of pelagic cephalopods that inhabit tropical and temperate oceans of the world. The family encompasses the modern paper nautiluses of the genus Argonauta along with several extinct genera of shelled octopods. Though argonauts are derived from benthic octopuses, they have evolved to depart the sea floor and live their life-cycle in the open seas.
The argonauts are a group of pelagic octopuses. They are also called paper nautiluses, referring to the paper-thin eggcase that females secrete. This structure lacks the gas-filled chambers present in chambered nautilus shells and is not a true cephalopod shell, but rather an evolutionary innovation unique to the genus Argonauta. It is used as a brood chamber, and to trap surface air to maintain buoyancy. It was once speculated that the argonauts did not manufacture their own eggcases but instead utilized shells abandoned by other organisms, in the manner of hermit crabs. Experiments by pioneering marine biologist Jeanne Villepreux-Power in the early 19th century disproved this hypothesis, as Villepreux-Power was able to successfully rear argonaut young and observe the development of their shells.
Argonauta argo, also known as the greater argonaut, is a species of pelagic octopus belonging to the genus Argonauta. The Chinese name for this species translates as "white sea-horse's nest".
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. This is to help avoid predators, because when seen from above, it blends in with the darkness of the sea, and when seen from below, it blends in with the light coming from above.
Argonauta nouryi, also known as Noury's argonaut, is a species of pelagic octopus. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The shell is usually approximately 80 mm in length, although it can exceed 90 mm in exceptional specimens; the world record size is 95.5 mm.
Argonauta hians, also known as the winged argonaut, muddy argonaut or brown paper nautilus, is a species of pelagic octopus. The common name comes from the grey to brown coloured shell. The Chinese name for this species translates as "Grey Sea-horse's Nest". The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The eggcase is characterised by a wide keel that gives it a square appearance, few rounded tubercles along the keel, and less than 40 smooth ribs across the sides of the shell. The shell is usually approximately 80 mm in length, although it can exceed 120 mm in exceptional specimens; the world record size is 121.5 mm.
Argonauta cornuta is a species of pelagic octopus belonging to the genus Argonauta. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus reminiscent of the way a nautilus lives in its shell. The shell is usually approximately 80 mm in length, although it can exceed 90 mm in exceptional specimens; the world record size is 98.6 mm.
Argonauta nodosa, also known as the knobby or knobbed argonaut, is a species of pelagic octopus. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The shell is usually approximately 150 mm in length, although it can exceed 250 mm in exceptional specimens; the world record size is 292.0 mm. A. nodosa produces a very characteristic shell, which is covered in many small nodules on the ridges across the shell, hence the specific epithet nodosa and common name. These nodules are less obvious or even absent in juvenile females, especially those under 5 cm in length. All other argonaut species have smooth ridges across the shell walls.
Argonauta bottgeri, also known as Böttger's argonaut, is a species of pelagic octopus belonging to the genus Argonauta. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell.
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 instantly 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. According to The Telegraph, "the allonautilus scrobiculatus has inhabited the earth for 500 million years and has only been seen twice, until now".
Allonautilus perforatus also known as the Bali chambered nautilus, is a species of nautilus native to the waters around Bali, Indonesia. It is known only from drifted shells and, as such, is the least studied of the six recognized nautilus species. Thus, not much is known about it outside of the shell.
Incirrata is a suborder of the order Octopoda. The suborder contains the classic "benthic octopuses," as well as many pelagic octopus families, including the paper nautiluses. The incirrate octopuses are distinguished from the cirrate octopuses by the absence in the former of the "cirri" filaments for which the cirrates are named, as well as by the lack of paired swimming fins on the head, and lack of a small internal shell.
Cephalopods vary enormously in size. The smallest are only about 1 centimetre (0.39 in) long and weigh less than 1 gram (0.035 oz) at maturity, while the largest—the giant and colossal squids—can exceed 10 metres (33 ft) in length and weigh close to half a tonne (1,100 lb), making them the largest living invertebrates. Living species range in mass more than three-billion-fold, or across nine orders of magnitude, from the lightest hatchlings to the heaviest adults. Certain cephalopod species are also noted for having individual body parts of exceptional size. The giant and colossal squids, for example, have the largest known eyes among living animals.
Obinautilus is an extinct genus of shelled cephalopod that has been variously identified as an argonautid octopod or a nautilid. It is known from the Late Oligocene to Pliocene of Japan. The shell is discoidal and very involute, with rapidly expanding and compressed whorls, fine radial ribs, a rounded venter with a shallow furrow, and almost closed umbilicus.
†Argonauta absyrtus is an extinct species of octopus assigned to the genus Argonauta.
Argonauta joanneus is an extinct species of octopus assigned to the genus Argonauta. It was described in 1915 based on fossil material from the Middle Miocene of Austria. It was found in fine sandy clay.
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.
Argonauta oweri is an extinct species of argonautid octopus. It is known from the early Pliocene of New Zealand.
Argonautoidea is a superfamily of the suborder Incirrata containing all known argonautoids.
