Nautilus

Nautilus

Overview
Nautilus is the common name of marine creatures of cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . 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...

 family Nautilidae, the sole extant family of the superfamily Nautilaceae
Nautilaceae
The Nautilaceae is one of five superfamilies that make up the Nautilida according to Bernard Kummel , and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilidae, Cymatoceratidae, Hercoglossidae, and Aturiidae...

 and of its smaller but near equal suborder, Nautilina
Nautilina
The Nautilina is the last suborder of the Nautilida and the only nautiloids living since the end of the Triassic. The Nautilina, proposed by Shimanskiy, is basically the Nautilaceae of Kummel, 1964, defined by Furnish and Glenister, but differs in omitting two families, the Paracenoceratidae and...

. It comprises six living species in two genera, the type
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...

 of which is the genus Nautilus
Nautilus (genus)
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...

. Though it more specifically refers to species Nautilus pompilius, the name chambered nautilus
Chambered Nautilus
The Chambered Nautilus, Nautilus pompilius, 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...

 is also used for any species of the Nautilidae.

Nautilidae, both extant and extinct, are characterized by involute
Involute
In the differential geometry of curves, an involute is a curve obtained from another given curve by attaching an imaginary taut string to the given curve and tracing its free end as it is wound onto that given curve; or in reverse, unwound. It is a roulette wherein the rolling curve is a straight...

 or slightly evolute
Evolute
In the differential geometry of curves, the evolute of a curve is the locus of all its centers of curvature. Equivalently, it is the envelope of the normals to a curve....

 shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle.
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Encyclopedia
Nautilus is the common name of marine creatures of cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . 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...

 family Nautilidae, the sole extant family of the superfamily Nautilaceae
Nautilaceae
The Nautilaceae is one of five superfamilies that make up the Nautilida according to Bernard Kummel , and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilidae, Cymatoceratidae, Hercoglossidae, and Aturiidae...

 and of its smaller but near equal suborder, Nautilina
Nautilina
The Nautilina is the last suborder of the Nautilida and the only nautiloids living since the end of the Triassic. The Nautilina, proposed by Shimanskiy, is basically the Nautilaceae of Kummel, 1964, defined by Furnish and Glenister, but differs in omitting two families, the Paracenoceratidae and...

. It comprises six living species in two genera, the type
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...

 of which is the genus Nautilus
Nautilus (genus)
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...

. Though it more specifically refers to species Nautilus pompilius, the name chambered nautilus
Chambered Nautilus
The Chambered Nautilus, Nautilus pompilius, 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...

 is also used for any species of the Nautilidae.

Nautilidae, both extant and extinct, are characterized by involute
Involute
In the differential geometry of curves, an involute is a curve obtained from another given curve by attaching an imaginary taut string to the given curve and tracing its free end as it is wound onto that given curve; or in reverse, unwound. It is a roulette wherein the rolling curve is a straight...

 or slightly evolute
Evolute
In the differential geometry of curves, the evolute of a curve is the locus of all its centers of curvature. Equivalently, it is the envelope of the normals to a curve....

 shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle. Having survived relatively unchanged for millions of years, nautiluses represent the only living members of the subclass Nautiloidea, and are often considered "living fossil
Living fossil
Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...

s."

The name "Nautilus" originally referred to the Argonauta, otherwise known as paper nautiluses, because the ancients believed these animals used their two expanded arms as sails (cf. Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 Historia Animalium
History of Animals
History of Animals is a zoological natural history text by Aristotle.-Arabic translation:The Arabic translation of Historia Animalium comprises treatises 1-10 of the Kitāb al-Hayawān .-See also:...

622b). However, this octopus is not closely related to the Nautiloidea.

Anatomy



The nautilus is similar in general form to other cephalopods, with a prominent head and tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

s. Nautiluses typically have more tentacles than other cephalopods, up to ninety. These tentacles are arranged into two circles and, unlike the tentacles of other cephalopods, they have no suckers, are undifferentiated and retractable. The radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...

 is wide and distinctively has nine teeth. There are two pairs of gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

s. These are the only remnants of the ancestral metamerism
Metamerism (biology)
In biology, metamerism is a linear series of body segments fundamentally similar in structure, though not all such structures are entirely alike in any single life form because some of them perform special functions....

 to be visible in extant cephalopods.

Nautilus pompilius is the largest species in the genus. One form from western Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 may reach 26.8 centimetres (10.6 in) in diameter. However, most other nautilus species never exceed 20 centimetres (7.9 in). Nautilus macromphalus
Bellybutton Nautilus
The Bellybutton Nautilus is a species of nautilus native to the waters off New Caledonia, the Loyalty Islands, and northeastern Australia. The shell of this species lacks a callus, leaving the umbilicus exposed, in which the inner coils of the shell are visible...

is the smallest species, usually measuring only 16 centimetres (6.3 in).

Shell



Nautiluses are the sole living cephalopods whose bony body structure is externalized as a shell. The animal can withdraw completely into its shell and close the opening with a leathery hood formed from two specially folded tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

s. The shell is coiled, aragonitic
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...

, nacreous and pressure resistant, imploding at a depth of about 800 metres (2,624.7 ft). The nautilus shell is composed of 2 layers: a matte
Matte
Matte may refer to:In film:* Matte , filmmaking and video production technology* Matte painting, a process of creating sets used in film and video* Matte box, a camera accessory for controlling lens glare...

 white outer layer, and a striking white iridescent
Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...

 inner layer. The innermost portion of the shell is a pearlescent blue-gray. The osmena pearl, contrarily to its name, is not a pearl
Pearl
A pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...

, but a jewellery
Jewellery
Jewellery or jewelry is a form of personal adornment, such as brooches, rings, necklaces, earrings, and bracelets.With some exceptions, such as medical alert bracelets or military dog tags, jewellery normally differs from other items of personal adornment in that it has no other purpose than to...

 product derived from this part of the shell.

Internally, the shell divides into camerae
Camerae
Camerae are the spaces or chambers enclosed between two adjacent septa in the phragmocone of a nautiloid or ammonoid cephalopod. These can be seen in cross-sections of a nautilus shell and in the polished cross-sections of ammonites...

 (chambers), the chambered section being called the phragmocone
Phragmocone
The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae.In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines buoyancy by means of gas...

. The divisions are defined by septa
Septa (biology)
Septa are thin walls or partitions between the internal chambers of the shell of a cephalopod, namely nautiloids or ammonoids....

, each of which is pierced in the middle by a duct, the siphuncle
Siphuncle
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 nautiluses, cuttlefish, and Spirula...

. As the nautilus matures it creates new, larger camerae, and moves its growing body into the larger space, sealing the vacated chamber with a new septum. The camerae increase in number from around four at the moment of hatching
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

 to thirty or more in adults.

The shell colouration also keeps the animal cryptic in the water. When seen from above, the shell is darker in color and marked with irregular stripes, which helps it blend into the dark water below. The underside is almost completely white, making the animal indistinguishable from brighter waters near the surface. This mode of camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

 is named countershading
Countershading
Countershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...

.

The nautilus shell presents one of the finest natural examples of a logarithmic spiral
Logarithmic spiral
A logarithmic spiral, equiangular spiral or growth spiral is a special kind of spiral curve which often appears in nature. The logarithmic spiral was first described by Descartes and later extensively investigated by Jacob Bernoulli, who called it Spira mirabilis, "the marvelous...

, although it is not a golden spiral
Golden spiral
In geometry, a golden spiral is a logarithmic spiral whose growth factor is , the golden ratio. That is, a golden spiral gets wider by a factor of for every quarter turn it makes.-Formula:...

. The use of nautilus shells in art and literature is covered at nautilus shell.

Tentacles


Nautilus tentacles differ from those of other cephalopods. Lacking pads, the tentacles stick to prey by virtue of their ridged surface. Nautiloids have a powerful grip. Attempts to take an object already seized by a nautilus may tear tentacles away from the creature, which remain firmly attached to the surface of the object. Two pairs of tentacles are separate from the other 90-ish, the pre-ocular and post-ocular, situated before and behind the eye. These are more evidently grooved, with more pronounced ridges. They are extensively ciliated and serve an olfactory purpose.

Buoyancy and movement




To swim, the nautilus draws water into and out of the living chamber with its hyponome
Hyponome
A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda. In other words, a siphon is found in some saltwater and freshwater snails, in some clams, and in octopus, squid and relatives.Siphons in molluscs are tube-like...

, which uses jet propulsion
Jet propulsion
Jet propulsion is motion produced by passing a jet of fluid in the opposite direction to the direction of motion. By conservation of momentum, the moving body is propelled in the opposite direction to the jet....

. While water is inside the chamber, the siphuncle
Siphuncle
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 nautiluses, cuttlefish, and Spirula...

 extracts salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 from it and diffuses it into the blood. The animal adjusts its buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...

 by osmotically
Osmosis
Osmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides...

 pumping gas and fluid into or out of the camerae along the siphuncles. This limits them; they cannot operate under the extreme hydrostatic pressures found at depths greater than approximately 800 metres (2,624.7 ft).

In the wild, nautiluses usually inhabit depths of about 300 metres (984.3 ft), rising to around 100 metres (328.1 ft) at night to feed, mate and to lay eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

.

Senses


Unlike many other cephalopods, they do not have good vision; their eye structure is highly developed but lacks a solid lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...

. They have a simple "pinhole
Pinhole camera
A pinhole camera is a simple camera without a lens and with a single small aperture – effectively a light-proof box with a small hole in one side. Light from a scene passes through this single point and projects an inverted image on the opposite side of the box...

" eye open to the environment.

Instead of vision, the animal is thought to use olfaction
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...

 as the primary sense for foraging
Foraging
- Definitions and significance of foraging behavior :Foraging is the act of searching for and exploiting food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce...

, locating or identifying potential mates.

Reproduction and lifespan


Nautiluses reproduce by laying egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

s. Gravid females attach the fertilized eggs to rocks in shallow waters, whereupon the eggs take eight to twelve months to develop until the 30 millimetres (1.2 in) juveniles hatch. Females spawn once per year and regenerate their gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...

s, making nautiluses the only cephalopods to present iteroparity or polycyclic spawning.

Nautiluses are sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

, in that males have four tentacles modified into an organ, called the "spadix," which transfers sperm into the female's mantle during mating. At sexual maturity, the male shell becomes slightly larger than the female's.

The lifespan of nautiluses may exceed 20 years, which is exceptionally lengthy for a cephalopod. However, nautiluses typically reach sexual maturity when they are about 15 years old.

Diet


Nautiluses are predators that feed mainly on small fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

, and other crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, which are captured by the tentacles. Due to the limited energy they expend in swimming, nautiloids only need to eat once a month.

Range, habitat, and status


Nautiluses are only found in the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...

, from 30° N to 30° S latitude and 90° to 185° W longitude. They inhabit the deep slopes of coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...

s. There is growing concern that nautiluses are being greatly overfished. Their limited ecological range and the late onset of their sexual maturity combined with this overfishing has led to recent investigations into the need to protect them from possible endangerment or extinction.

Evolution



Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 records indicate that nautiluses have not evolved much during the last 500 million years. Many were initially straight-shelled, as in the extinct genus Lituites
Lituites
Lituites is an extinct nautiloid genus from the Middle Ordovician and type for the Lituitidae, a tarphycerid family that in some more recent taxonomies has been classified with the orthocerids and listed under the order Lituitida...

. They developed in the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 period and became a significant sea predator in the Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 period. Certain species reached over 2.5 metres (8.2 ft) in size. The other cephalopod subclass, Coleoidea
Coleoidea
Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the primarily soft-bodied creatures. Unlike its sister group Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal bone or shell that is used for buoyancy or support...

, diverged from the Nautilidae long ago and the nautilus has remained relatively unchanged since. Nautiloids were much more extensive and varied 200 million years ago. Extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 relatives of the nautilus include ammonite
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...

s, such as the baculite
Baculite
Baculites is an extinct cephalopod genus with a nearly straight shell that is included in the heteromorph ammonites...

s and goniatites
Goniatites
Goniatites is genus of the Goniatitaceae superfamily. They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopuses, and cuttlefish, and more distantly to the nautiloids.-References:* accessed on 10/01/07...

.

The Nautilidae has its origin in the Trigonocerataceae
Trigonocerataceae
The Trigonocerataceae is a superfamily within the Nautilida that ranged from the Devonian to the Triassic that is thought to have contained the source for the Nautilaceae in which Nautilus is found....

 (Centroceratina), specifically in the Syringonautilidae
Syringonautilidae
The Syringonautilidae comprise the last of the Trigonocerataceae and are the source for the Nautilaceae which continued the Nautiloidea through the Mesozoic and into the Cenozoic right down to the recent. The Syringonautilidae, itself, is a strictly Triassic family, derived early in the Triassic...

 of the Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...

 and continues to this day with Nautilus
Nautilus (genus)
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...

, the type genus, and its close relative, Allonautilus
Allonautilus
The genus Allonautilus contains two species of nautiluses, which differ significantly in terms of morphology from those placed in the sister taxon Nautilus. Allonautilus is now thought to be a descendant of Nautilus and the latter paraphyletic.-External links:*...

.

Fossil genera


The Nautilidae begin with Cenoceras
Cenoceras
The genus Cenoceras is a member of the Nautilidae, which in turn makes up part of the superfamily Nautilaceae.Cenoceras is variable in form, depending on species; ranges from evolute to involute, compressed lenticular to globose with rounded to flattened venter and flanks. The suture generally has...

in the Late Triassic, a highly varied genus that makes up the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 Cenoceras complex. Cenoceras is evolute to involute, and globular to lentincular; with a suture that generally has a shallow ventral and lateral lobe and a siphuncle that is variable in position but never extremely ventral or dorsal. Cenoceras is not found above the Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....

 and is followed by the Upper Jurassic-Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 Eutrephoceras.

Eutrephoceras is generally subgobular, broadly rounded laterally and ventrally, with a small to occluded umbilicus, broadly rounded hyponomic sinus, only slightly sinuous sutures, and a small siphuncle that is variable in position.

Next to appear is the Lower Cretaceous Strionautilus from India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 and the European ex-USSR, named by Shimankiy in 1951. Strionautilus is compressed, involute, with fine longitudinal striations. Whorl sections are subrectangular, sutures sinuous, the siphuncle subcentral.

Also from the Cretaceous is Pseudocenoceras, named by Spath in 1927. Pseudocenoceras is compressed, smooth, with subrectangular whorl sections, flattened venter, and a deep umbilicus. The suture crosses the venter essentially straight and has a broad, shallow, lateral lobe. The siphuncle is small and subcentral. Pseudocenoceras is found in the Crimea
Crimea
Crimea , or the Autonomous Republic of Crimea , is a sub-national unit, an autonomous republic, of Ukraine. It is located on the northern coast of the Black Sea, occupying a peninsula of the same name...

 and in Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....

.

Carinonautilus is a genus from the Upper Cretaceous of India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, named by Spengler in 1919. Carinonautilus is a very involute form with high whorl section and flanks that converge on a narrow venter that bears a prominent rounded keel. The umbilicus is small and shallow, the suture only slightly sinuous. The siphuncle is unknown.

Taxonomy



The family Nautilidae contains six extant species and several extinct species
Extinct species
This page features extinct species, organisms that have become extinct.* List of extinct animals* List of extinct plants...

.
  • Genus Allonautilus
    Allonautilus
    The genus Allonautilus contains two species of nautiluses, which differ significantly in terms of morphology from those placed in the sister taxon Nautilus. Allonautilus is now thought to be a descendant of Nautilus and the latter paraphyletic.-External links:*...

    • A. perforatus
      Allonautilus perforatus
      Allonautilus perforatus 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 recognised nautilus species....

    • A. scrobiculatus
      Crusty Nautilus
      Allonautilus scrobiculatus, also known as the Crusty 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 recognisable by the large open umbilicus, which is around 20% of the shell...

  • Genus Nautilus
    Nautilus (genus)
    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...

    • N. belauensis
      Palau Nautilus
      Nautilus belauensis, also known as the Palau Nautilus, is a species of nautilus native to the waters around the Pacific island nation of Palau. N. belauensis is very similar to Nautilus pompilius and shares with this species a closed umbilicus covered with a callus...

    • N. cookanum
      Nautilus cookanum
      Nautilus cookanum is an extinct species of nautilus. It lived during the Eocene epoch. N. cookanum has been grouped into a single taxon together with extant species based on their shared shell characters. Fossils of the species from the Late Eocene Hoko River Formation are noted as one of the two...

    • N. macromphalus
      Bellybutton Nautilus
      The Bellybutton Nautilus is a species of nautilus native to the waters off New Caledonia, the Loyalty Islands, and northeastern Australia. The shell of this species lacks a callus, leaving the umbilicus exposed, in which the inner coils of the shell are visible...

    • N. pompilius (type
      Type species
      In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

      )
      • N. p. pompilius
      • N. p. suluensis
    • N. praepompilius
      Nautilus praepompilius
      Nautilus praepompilius is an extinct species of nautilus. It lived during the Late Eocene through Oligocene epochs. Fossil specimens have been uncovered from the Chegan Formation of Kazakhstan. N. praepompilius has been grouped into a single taxon together with extant species based on their shared...

    • N. stenomphalus
      White-patch Nautilus
      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...


Dubious or uncertain taxa


The following taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 associated with the family Nautilidae are of uncertain taxonomic status:
Binomial name and author citation Current systematic status Type locality Type repository
N. alumnus Iredale
Tom Iredale
Tom Iredale was an English-born ornithologist and malacologist who had a long association with Australia, where he lived for most of his life. He was an autodidact who never went to university and lacked formal training...

, 1944
Species dubium [fide Saunders (1987:49)] Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 
Not designated [fide Saunders (1987:49)]
N. ambiguus Sowerby, 1848 Species dubium [fide Saunders (1987:48)] Not designated Unresolved
N. beccarii Linne, 1758 Non-cephalopod; Foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

 [fide Frizzell and Keen (1949:106)]
N. calcar Linne, 1758 ?Non-cephalopod; Foraminifera Lenticulina Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. crispus Linne, 1758 Undetermined Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. crista Linne, 1758 Non-cephalopod; Turbo [fide Dodge (1953:14)]
N. fascia Linne, 1758 Undetermined Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. granum Linne, 1758 Undetermined Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. lacustris Lightfoot
John Lightfoot FRS
The Reverend John Lightfoot was an English conchologist and botanist.He was born in Newent, Gloucestershire and educated at Pembroke College, Oxford. He gained a BA in 1756 and an MA in 1766....

, 1786
Non-cephalopod; Helix
Helix (genus)
Helix is a genus of large air-breathing land snails, terrestrial pulmonate gastropod molluscs. This genus is native to Europe and the regions around the Mediterranean Sea. Helix is the type genus of the family Helicidae....

[fide Dillwyn
Lewis Weston Dillwyn
Lewis Weston Dillwyn, FRS was a British porcelain manufacturer, naturalist and Member of Parliament.He was born in Walthamstow, Essex, the eldest son of William Dillwyn and Sarah Dillwyn...

 (1817:339)]
N. legumen Linne, 1758 Undetermined Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. micrombilicatus Joubin, 1888 Nomen nudum
Nomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...

N. obliquus Linne, 1758 Undetermined Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. pompilius marginalis Willey, 1896 Species dubium [fide Saunders (1987:50)] New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

 
Unresolved
N. pompilius moretoni Willey, 1896 Species dubium [fide Saunders (1987:49)] New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

 
Unresolved
N. pompilius perforatus Willey, 1896 Species dubium [fide Saunders (1987:49)] New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

 
Unresolved
N. radicula Linne, 1758 ?Non-cephalopod; Foraminifera Nodosaria Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. raphanistrum Linne, 1758 Undetermined Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. raphanus Linne, 1758 Undetermined Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. semi-lituus Linne, 1758 Undetermined Liburni, Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

 
Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. sipunculus Linne, 1758 Undetermined "freto Siculo" Unresolved; Linnean Society of London
Linnean Society of London
The Linnean Society of London is the world's premier society for the study and dissemination of taxonomy and natural history. It publishes a zoological journal, as well as botanical and biological journals...

?
N. texturatus Gould, 1857 Nomen nudum
Nomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...

Octopodia nautilus Schneider, 1784 Rejected specific name [fide Opinion 233, ICZN (1954:278)]

In popular culture


The nautilus shell features prominently in the official emblem
Emblem of New Caledonia
The emblem of New Caledonia consists of a nautilus shell in the foreground; the symbol behind it is a flèche faitière, a kind of arrow which adorns the roofs of Kanak houses, thrust through tutut shells....

 of New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...

.

See also


  • Cephalopod size
    Cephalopod size
    Size has been one of the most interesting aspects of cephalopod science to the general public. This article lists the largest cephalopods from various groups, sorted in order of mantle length, total length, weight, and shell diameter...

    , for maximum shell diameters
  • History of animals by Conrad Gesner
    Historiae animalium (Gesner)
    Historiae animalium published at Zurich in 1551-58 and 1587, is an encyclopedic work of "an inventory of renaissance zoology" by Conrad Gesner, a doctor and professor at the Carolinum, the precursor of the University of Zurich...

    , first book with fossil illustrations.
  • The Nautilus
    The Nautilus (journal)
    The Nautilus is a peer-reviewed scientific journal covering research in malacology. Hence its scope includes all aspects of the biology, ecology, and systematics of mollusks....

    , a malacological journal
  • The Chambered Nautilus, a poem of Oliver Wendell Holmes
    Oliver Wendell Holmes, Sr.
    Oliver Wendell Holmes, Sr. was an American physician, professor, lecturer, and author. Regarded by his peers as one of the best writers of the 19th century, he is considered a member of the Fireside Poets. His most famous prose works are the "Breakfast-Table" series, which began with The Autocrat...


External links