Editing Nautilus

{{Short description|Family of molluscs}}
{{About|the marine mollusc family Nautilidae|ships of the same name|List of ships named Nautilus|other uses}}
{{Automatic taxobox
| name = Nautilus
| fossil_range = [[Triassic]]{{en dash}}present {{Fossil range|230|0|ref=<ref>{{Cite journal| journal = Journal of Paleontology| year = 1997| volume = 71| issue = 6| title = ''Allonautilus'': A New Genus of Living Nautiloid Cephalopod and Its Bearing on Phylogeny of the Nautilida| last1 = Ward| first1 = P. D.| last2 = Saunders| first2 = W. B.| jstor = 1306604| pages = 1054–1064| doi = 10.1017/S0022336000036039| bibcode = 1997JPal...71.1054W| s2cid = 87319305}}</ref>}}
| image = Nautilus belauensis from Palau.jpg
| image_caption = ''[[Palau Nautilus|Nautilus belauensis]]''
| status = CITES_A2
| status_system = CITES
| taxon = Nautilidae
| authority = [[Henri Marie Ducrotay de Blainville|Blainville]], 1825
| subdivision_ranks = Genera
| subdivision = †''[[Carinonautilus]]''<br/>
†''[[Cenoceras]]''<br/>
†''[[Eutrephoceras]]''<br/>
†''[[Pseudocenoceras]]''<br/>
†''[[Strionautilus]]''<br/>
''[[Allonautilus]]''<br/>
''[[Nautilus (genus)|Nautilus]]''<br/>
† = Extinct
| synonyms_ref = <ref>{{cite journal |last1=Cichowolski|first1=M. |last2=Ambrosio|first2=A. |last3=Concheyro|first3=A. |doi=10.1017/S0954102005002671 |title=Nautilids from the Upper Cretaceous of the James Ross Basin, Antarctic Peninsula |journal=[[Antarctic Science]] |volume=17 |issue=2 |page=267 |year=2005 |bibcode=2005AntSc..17..267C |s2cid=128767860 |hdl=11336/96152 |hdl-access=free }}</ref>
| synonyms = *Eutrephoceratidae <small>Miller, 1951</small>
}}

A '''nautilus''' ({{etymology|la|{{wikt-lang|la|nautilus}}|sails like a vessel}}; {{etymology|grc|''{{wikt-lang|grc|ναυτίλος}}'' ({{grc-transl|ναυτίλος}})|seaman, sailor }})<ref>{{cite encyclopedia |url= https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dnautilus |title= nautĭlus or nautĭlŏs |last1= Lewis |first1= Charlton T. |author1-link=Charlton T. Lewis |last2= Short |first2= Charles|author2-link=Charles Short |dictionary= A Latin Dictionary |edition= |publisher= [[Perseus Digital Library]] |date = 1879 }}</ref> {{efn|The word originally referred to a type of [[Mediterranean]]<ref name=Prescott>{{Cite journal|last1= Prescott|first1=Henry W.|author1-link=Henry W. Prescott |url=https://www.jstor.org/stable/262901  |date=October 1921|title=Callimachus' Epigram on the Nautilus|journal=[[Classical Philology (journal)|Classical Philology]]|volume=16|issue=4|publisher=[[University of Chicago Press]]|doi=|issn=|arxiv=|bibcode=|s2cid=|doi-access=}}</ref> [[cephalopod]] [[mollusc]] ''[[Argonauta argo#Gallery|Argonauta argo]]'', also known as 'paper nautilus', which were thought to use their membrane arms as sails.<ref>{{cite web|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dnauti/los |title=ναυτίλος |last1=Liddell |first1=Henry George |last2=Scott |first2=Robert |work=A Greek-English Lexicon |publisher=Perseus Digital Library |date= 1940 }}</ref> [[Ancient Greek]] usage: [[Aristotle]]. [[Callimachus]] - [[Callimachus#Epigrams|Epigram]]<ref name=Prescott/> V.<ref>{{cite web|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0226%3Atext%3Depigrams%3Apoem%3D5|website=www.perseus.tufts.edu|title=Callimachus, Epigrams|date=|editor=Ulrich von Wilamowitz-Moellendorff|editor-link=Ulrich von Wilamowitz-Moellendorff|publisher=|access-date=|url-status=|archive-url=|archive-date=}}</ref>}} is any of the various species within the [[cephalopod]] family '''Nautilidae'''. This is the sole extant family of the superfamily [[Nautilaceae]] and the suborder [[Nautilina]].

It comprises nine living species in two genera, the [[type genus|type]] of which is the genus ''[[Nautilus (genus)|Nautilus]]''. Though it more specifically refers to the species ''[[chambered nautilus|Nautilus pompilius]]'', the name [[chambered nautilus]] is also used for any of the Nautilidae. All are protected under [[CITES]] [[CITES Appendix II|Appendix II]].<ref>{{cite web |title=Checklist of CITES species |url=http://checklist.cites.org |publisher=[[CITES]] |access-date=24 June 2020}} (please fill in 'Nautilus' in the search-box).</ref> Depending on species, adult shell diameter is between {{convert|4|and|10|in|cm|abbr=in|order=flip}}.

The Nautilidae, both extant and extinct, are characterized by [[involute]] or more or less convoluted shells that are generally smooth, with compressed or depressed [[whorl (mollusc)|whorl]] sections, straight to sinuous [[Suture (anatomy)|suture]]s, and a tubular, generally central [[siphuncle]].<ref name=Kummel>Kümmel, B. 1964. Nautiloidae-Nautilida, in the [[Treatise on Invertebrate Paleontology]], Geological Society of America and Univ of Kansas Press, Teichert and Moore eds.</ref> Having survived relatively unchanged for hundreds of millions of years, nautiluses represent the only living members of the subclass [[Nautiloidea]], and are often considered "[[living fossil]]s".
[[File:The_first_and_oldest_fossil_of_Chambered_Nautilus_displayed_at_Philippine_National_Museum.jpg|thumb|The first and oldest fossil of [[chambered nautilus]] displayed at [[National Museum of the Philippines|Philippine National Museum]].]]

==Anatomy==
[[File:Nautilus diagram-en.svg|upright=1.8|thumb|Diagram of the anatomical structure of a female ''N. pompilius'' including most of its internal organs.]]

===Tentacles===
The arm crown of modern nautilids (genera ''[[Nautilus (genus)|Nautilus]]'' and ''[[Allonautilus]]'') is very distinct in comparison to coleoids. Unlike the ten-armed [[Squid|Decabrachia]] or the eight-armed [[Octopodiformes]], nautilus may possess any number of tentacles (cirri) from 50 to  over 90 tentacles depending on the sex and individual.<ref>{{cite journal |last1=Kröger |first1=Björn |last2=Vinther |first2=Jakob |last3=Fuchs |first3=Dirk |title=Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules: Extant cephalopods are younger than previously realised and were under major selection to become agile, shell-less predators |journal=BioEssays |date=August 2011 |volume=33 |issue=8 |pages=602–613 |doi=10.1002/bies.201100001|pmid=21681989 |s2cid=2767810 }}</ref><ref name=":1">{{cite book |last1=Sasaki |first1=T |last2=Shigeno |first2=S|last3=Tanabe |first3=K |date=2010 |title=Cephalopods - Present and Past |publisher=Tokai University Press |chapter=Anatomy of living Nautilus: reevaluation of primitiveness and comparison with Coeloidea |name-list-style=amp}}</ref> These tentacles are classified into three distinct categories: ocular, digital, and labial (buccal).<ref name=":2">{{cite book |last1=Owen |first1=Richard |title=Memoir on the pearly nautilus (Nautilus pompilius, Linn). With illustrations of its external form and internal structure |date=1832 |publisher=Richard Taylor |location=London |url=https://www.biodiversitylibrary.org/bibliography/10441}}</ref> There are two sets of ocular tentacles: one set in front of the eye (pre-ocular) and one set behind the eye (post-ocular). The digital and labial tentacles are arrayed circularly around the mouth, with the digital tentacles forming the outermost ring and the labial tentacles in between the digital tentacles and the mouth. There are 19 pairs of digital tentacles that, together with the ocular tentacles, make up the 42 appendages that are visible when observing the animal (not counting the modified tentacles that form the hood). The labial tentacles are generally not visible, being smaller than the digital tentacles, and more variable both in number and in shape.<ref name=":1" /><ref name=":2" /><ref>{{Cite journal |last=Griffin |first=Lawrence E. |date=1899 |title=XXVI.— Notes on the tentacles of Nautilus pompilius |journal=Annals and Magazine of Natural History |language=en |volume=3 |issue=14 |pages=170–176 |doi=10.1080/00222939908678098 |issn=0374-5481|url=https://www.biodiversitylibrary.org/part/58804 }}</ref> Males modify three of their labial tentacles into the [[Spadix (zoology)|spadix]], which delivers [[spermatophore]]s into the female during copulation.<ref name=":1" />

The tentacle is composed of two distinct structures: the first structure, a fleshy sheath that contains the second structure: an extendable [[cirrus (biology)|cirrus]] (plural: cirri).<ref name=":2" /><ref name=":3">{{Citation |last=Kier |first=William M. |title=The Functional Morphology of the Tentacle Musculature of Nautilus pompilius |date=2010 |url=https://doi.org/10.1007/978-90-481-3299-7_18 |work=Nautilus: The Biology and Paleobiology of a Living Fossil, Reprint with additions |pages=257–269 |editor-last=Saunders |editor-first=W. Bruce |access-date=2023-11-28 |series=Topics in Geobiology |volume=6 |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-90-481-3299-7_18 |isbn=978-90-481-3299-7 |editor2-last=Landman |editor2-first=Neil H.|url-access=subscription }}</ref> The sheaths of the digital tentacles are fused at their base into a single mass referred to as the cephalic sheath. The digital cirri can be fully withdrawn into the sheath and are highly flexible, capable of extending just over double their fully retracted length and show a high degree of allowable bendability and torsion.<ref name=":3" /> Despite not having suckers, the digital tentacles show strong adhesive capabilities. Adhesion is achieved through the secretion of a neutral (rather than acidic) [[Glycosaminoglycan|mucopolysaccharide]] from secretory cells in the ridges of the digital cirri.<ref>{{Citation |last=Fukuda |first=Yoshio |title=Histology of the Long Digital Tentacles |date=2010 |url=https://doi.org/10.1007/978-90-481-3299-7_17 |work=Nautilus: The Biology and Paleobiology of a Living Fossil, Reprint with additions |pages=249–256 |editor-last=Saunders |editor-first=W. Bruce |access-date=2023-11-28 |series=Topics in Geobiology |volume=6 |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-90-481-3299-7_17 |isbn=978-90-481-3299-7 |editor2-last=Landman |editor2-first=Neil H.|url-access=subscription }}</ref><ref>{{Cite journal |last1=Muntz |first1=W. R. A. |last2=Wentworth |first2=S. L. |date=1995 |title=Structure of the Adhesive Surface of the Digital Tentacles of Nautilus Pompilius |journal=Journal of the Marine Biological Association of the United Kingdom |language=en |volume=75 |issue=3 |pages=747–750 |doi=10.1017/S0025315400039163 |bibcode=1995JMBUK..75..747M |s2cid=83497566 |issn=1469-7769}}</ref><ref name=":4">{{Cite journal |last1=von Byern |first1=Janek |last2=Wani |first2=Ryoji |last3=Schwaha |first3=Thomas |last4=Grunwald |first4=Ingo |last5=Cyran |first5=Norbert |date=2012-02-01 |title=Old and sticky—adhesive mechanisms in the living fossil Nautilus pompilius (Mollusca, Cephalopoda) |journal=Zoology |volume=115 |issue=1 |pages=1–11 |doi=10.1016/j.zool.2011.08.002 |issn=0944-2006 |pmc=3311398 |pmid=22221553|bibcode=2012Zool..115....1V }}</ref> Release is triggered through contraction of the tentacle musculature rather than the secretion of a chemical solvent, similar to the adhesion/release system in ''[[Euprymna]]'', though it is unclear whether these adhesives are [[Homology (biology)|homologous]].<ref name=":4" /><ref>{{Cite journal |last1=von Byern |first1=Janek |last2=Cyran |first2=Norbert |last3=Klepal |first3=Waltraud |last4=Nödl |first4=Marie Therese |last5=Klinger |first5=Lisa |date=February 2017 |title=Characterization of the adhesive dermal secretion of Euprymna scolopes Berry, 1913 (Cephalopoda) |url=https://linkinghub.elsevier.com/retrieve/pii/S0944200616300836 |journal=Zoology |language=en |volume=120 |pages=73–82 |doi=10.1016/j.zool.2016.08.002|pmid=27646066 |bibcode=2017Zool..120...73V |url-access=subscription }}</ref> The ocular tentacles show no adhesive capability but operate as sensory organs. Both the ocular tentacles and the eight lateral digital tentacles show chemoreceptive abilities; the preocular tentacles detect distant odor and the lateral digital tentacles detect nearby odor.<ref>{{Cite journal |last1=Basil |first1=Jennifer |last2=Bahctinova |first2=Irina |last3=Kuroiwa |first3=Kristine |last4=Lee |first4=Nandi |last5=Mims |first5=Desiree |last6=Preis |first6=Michael |last7=Soucier |first7=Christian |date=2005 |title=The function of the rhinophore and the tentacles of Nautilus pompilius L. (Cephalopoda, Nautiloidea) in orientation to odor |journal=Marine and Freshwater Behaviour and Physiology |language=en |volume=38 |issue=3 |pages=209–221 |doi=10.1080/10236240500310096 |bibcode=2005MFBP...38..209B |s2cid=33835096 |issn=1023-6244}}</ref><ref>{{Cite journal |last1=Ruth |first1=Peter |last2=Schmidtberg |first2=Henrike |last3=Westermann |first3=Bettina |last4=Schipp |first4=Rudolf |date=March 2002 |title=The sensory epithelium of the tentacles and the rhinophore of Nautilus pompilius L. (cephalopoda, nautiloidea) |journal=Journal of Morphology |volume=251 |issue=3 |pages=239–255 |doi=10.1002/jmor.1086 |issn=0362-2525 |pmid=11835362|s2cid=38377665 }}</ref>

===Digestive system===
The [[radula]] is wide and distinctively has nine teeth.

The mouth consists of a [[cephalopod beak|parrot-like beak]] made up of two interlocking jaws capable of ripping the animal's food— mostly crustaceans— from the rocks to which they are attached.<ref name=grif>{{Cite book
|title=The anatomy of ''Nautilus pompilius''
|last=Griffin
|first=Lawrence E.
|volume=8
|year=1900
|publisher=Government Printing Office
|place=Washington, D.C.
|url={{google books |plainurl=y |id=IHJBAQAAIAAJ}}
|oclc=18760979
|doi=10.5962/bhl.title.10466
}}</ref>{{rp|p. 105}} Males can be superficially differentiated from females by examining the arrangement of tentacles around the buccal cone: males have a [[Spadix (zoology)|spadix]] organ (shaped like a spike or shovel) located on the left side of the cone making the cone look irregular, whereas the buccal cone of the female is [[Symmetry in biology|bilaterally symmetrical]].<ref name=grif/>{{rp|pp. 115–130}}

The crop is the largest portion of the digestive tract, and is highly extensible. From the crop, food passes to the small muscular stomach for crushing, and then goes past a digestive caecum before entering the relatively brief intestine.

===Circulatory system===
Like all cephalopods, the blood of the nautilus contains [[hemocyanin]], which is blue in its oxygenated state. There are two pairs of [[gill]]s which are the only remnants of the ancestral [[Metamerism (biology)|metamerism]] to be visible in extant cephalopods.<ref name=Wingstrand1985>{{cite journal
|url=http://www.zmuc.dk/inverweb/Galathea/Galathea_p5.html
|format=Link to free full text + plates
|last=Wingstrand
|first=KG
|year=1985
|title=On the anatomy and relationships of Recent Monoplacophora
|journal=Galathea Rep.
|volume=16
|pages=7–94
|access-date=2009-04-21
|archive-url=https://web.archive.org/web/20160303182836/http://www.zmuc.dk/inverweb/Galathea/Galathea_p5.html
|archive-date=2016-03-03
|url-status=dead
}}</ref>{{rp|56}} Oxygenated blood arrives at the heart through four ventricles and flows out to the animal's organs through distinct aortas but returns through veins which are too small and varied to be specifically described. The one exception to this is the vena cava, a single large vein running along the underside of the crop into which nearly all other vessels containing deoxygenated blood empty. All blood passes through one of the four sets of filtering organs (composed of one pericardial appendage and two renal appendages) upon leaving the vena cava and before arriving at the gills for re-oxygenation. Blood waste is emptied through a series of corresponding pores into the [[pallial cavity]].

===Nervous system===
The central component of the nautilus nervous system is the oesophageal [[nerve ring]] which is a collection of [[ganglia]], [[commissure]]s, and connectives that together form a ring around the animal's oesophagus. From this ring extend all of the nerves forward to the mouth, tentacles, and funnel; laterally to the eyes and [[rhinophore]]s; and posteriorly to the remaining organs.

The nerve ring does not constitute what is typically considered a cephalopod "brain": the upper portion of the nerve ring lacks differentiated lobes, and most of the nervous tissue appears to focus on finding and consuming food (i.e., it lacks a "higher learning" center). Nautili also tend to have rather short memory spans, and the nerve ring is not protected by any form of brain case.<ref>{{cite journal
 | last =Young
 | first =J. Z.
 | title =The Central Nervous System of Nautilus
 | journal =Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
 | volume =249
 | issue =754
 | pages =1–25
 | date =27 May 1965
 | jstor =2416631
 | doi =10.1098/rstb.1965.0006
 | bibcode =1965RSPTB.249....1Y
 | s2cid =83951270
 | doi-access =
 }}</ref>

===Shell===
[[Image:NautilusCutawayLogarithmicSpiral.jpg|thumb|Nautilus half-shell showing the camerae in a [[logarithmic spiral]]|alt=]][[File:Nautilus Section cut.jpg|thumb|Section cut of a nautilus shell]]
{{multiple image
| align = right
| total_width = 220
| image1 = NautilusTop.jpg
| alt1 = 
| caption1 = 
| image2 = NautilusBottom.jpg
| alt2 = 
| caption2 = 
| footer = A nautilus shell viewed from above (left), and from underneath  (right)
}}

Nautili are the sole living cephalopods whose bony body structure is externalized as a planispiral [[Exoskeleton|shell]]. The animal can withdraw completely into its shell and close the opening with a leathery hood formed from two specially folded [[tentacle]]s. The shell is coiled, [[aragonite|aragonitic]],<ref>{{Cite journal| last1 = Buchardt| first1 = B.| title = Diagenesis of aragonite from Upper Cretaceous ammonites: a geochemical case-study| journal = Sedimentology| volume = 28| issue =  3| pages = 423–438| year = 1981| doi = 10.1111/j.1365-3091.1981.tb01691.x| last2 =  Weiner| first2 = S.|bibcode = 1981Sedim..28..423B }}</ref> [[nacre]]ous and pressure-resistant, imploding at a depth of about {{cvt|800|m|ft|-2}}. The nautilus shell is composed of two layers: a [[Gloss (material appearance)|matte]] white outer layer with dark orange stripes,<ref>{{cite web |url= https://marinesanctuary.org/blog/sea-wonder-chambered-nautilus/ |title= Sea Wonder: Chambered Nautilus |date= 21 August 2021 |website= National Marine Sanctuary Foundation |access-date= 26 November 2022}}</ref> and a striking white [[iridescence|iridescent]] inner layer. The innermost portion of the shell is a pearlescent blue-gray. The [[osmeña pearl]], contrarily to its name, is not a [[pearl]], but a [[jewellery]] product derived from this part of the shell.{{Citation needed|date=August 2024}}

Internally, the shell divides into [[Camera (cephalopod)|camerae]] (chambers), the chambered section being called the [[phragmocone]]. The divisions are defined by [[Septa (biology)|septa]], each of which is pierced in the middle by a duct, the [[siphuncle]]. 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 4 at the moment of [[egg (biology)|hatching]] to 30 or more in adults.

The shell coloration also keeps the animal [[cryptic (zoology)|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]] is called [[countershading]].

The nautilus shell presents one of the finest natural examples of a [[logarithmic spiral]], although it is not a [[golden spiral]]. The use of nautilus shells in art and literature is covered at [[Chambered Nautilus#In literature and art|nautilus shell]].

===Size===
''N. pompilius'' is the largest species in the genus. One form from [[Indonesia]] and northern [[Australia]], once called ''N. repertus'', may reach {{cvt|25.4|cm}} in diameter.<ref>Pisor, D.L. (2008). ''[[Registry of World Record Size Shells]]''. Fifth edition. ConchBooks, Hackenheim. 207&nbsp;pp. {{ISBN|0615194753}}.</ref> However, most nautilus species never exceed {{cvt|20|cm|in|0}}. ''[[Bellybutton Nautilus|Nautilus macromphalus]]'' is the smallest species, usually measuring only {{cvt|16|cm|in|frac=2}}. A dwarf population from the [[Sulu Sea]] (''[[Nautilus pompilius suluensis]]'') is even smaller, with a mean shell diameter of {{cvt|11.56|cm}}.<ref name="Dunstan et al. 2011" />

==Physiology==

===Buoyancy and movement===
[[File:Nautilus.ogv|thumb|Nautilus locomotion<br/>File format: Ogg<br/>File size: 1.29 MB<br/>Duration: 5 seconds|alt=Video]]
[[Image:Nautilus oceanworld thailand.png|thumb|left|upright|Nautilus with extended tentacles and hyponome visible|alt=]]

To swim, the nautilus draws water into and out of the living chamber with its [[hyponome]], which uses [[jet propulsion]]. This mode of propulsion is generally considered inefficient compared to propulsion with fins or [[undulatory locomotion]], however, the nautilus has been found to be particularly efficient compared to other jet-propelled marine animals like [[squid]] and [[jellyfish]], or even [[salmon]] at low speeds.<ref>{{Cite journal|title=Swimming mechanics and propulsive efficiency in the chambered nautilus|journal=Royal Society Open Science|volume=5|issue=2|page=170467|doi=10.1098/rsos.170467|pmc=5830708|pmid=29515819|year = 2018|last1 = Neil|first1 = T. R.|last2=Askew|first2=G. N.|bibcode=2018RSOS....570467N}}</ref> It is thought that this is related to the use of asymmetrical contractile cycles and may be an adaptation to mitigate metabolic demands and protect against [[Hypoxia (environmental)|hypoxia]] when foraging at depth.<ref>{{Cite book|last=Askew|first=Graham|date=2017|title=Dataset associated with study on swimming mechanics and propulsive efficiency in the chambered nautilus|chapter-url=http://archive.researchdata.leeds.ac.uk/305/|language=en|publisher=University of Leeds|doi=10.5518/192|type=Data Set|chapter=B120}}</ref> While water is inside the chamber, the [[siphuncle]] extracts [[salt]] from it and diffuses it into the blood.

The animal adjusts its [[buoyancy]] only in long term density changes by [[osmosis]], either removing liquid from its chambers or allowing water from the blood in the siphuncle to slowly refill the chambers. This is done in response to sudden changes in buoyancy that can occur with predatory attacks of fish, which can break off parts of the shell. This limits nautiluses in that they cannot operate under the extreme [[hydrostatic pressure]]s found at depths greater than approximately {{convert|800|m}}, and in fact implode at about that depth, causing instant death.<ref name="Dunstan et al. 2011" /> The gas also contained in the chambers is slightly below atmospheric pressure at sea level.<ref>{{cite book |last1= Saunders |first1= W. Bruce |last2= Landman |first2=Neil H. |orig-date= 1987 |year=2009 |title= Nautilus: The Biology and Paleobiology of a Living Fossil | edition = 2nd |publisher= Springer Netherlands |page= 552 |isbn=978-90-481-3298-0 }}</ref> The maximum depth at which they can regulate buoyancy by osmotic removal of chamber liquid is not known.<ref name=Ward1987 />

The nautilus has the extremely rare ability to withstand being brought to the surface from its deep natural habitat without suffering any apparent damage from the experience. Whereas fish or crustaceans brought up from such depths inevitably arrive dead, a nautilus will be unfazed despite the pressure change of as much as {{convert|80|atm|psi|lk=in}}. The exact reasons for this ability, which is thought to be coincidental rather than specifically functional, are not known, though the perforated structure of the animal's [[vena cava]] is thought to play an important role.<ref name=grif/>{{rp|p. 188}}

===Senses===
[[File:Nautilus pompilius (head).jpg|thumb|Head of ''N. pompilius'' showing the rudimentary eye, which functions similarly to a [[pinhole camera]]]]

Unlike many other cephalopods, nautiluses do not have what many consider to be good vision; their [[eye]] structure is highly developed but lacks a solid [[lens (anatomy)|lens]]. Whereas a sealed lens allows for the formation of highly focused and clear, detailed surrounding imagery, nautiluses have a simple [[Pinhole camera|pinhole]] eye open to the environment which only allows for the creation of correspondingly simple imagery.

Instead of vision, the animal is thought to use [[olfaction]] (smell) as the primary sense for [[foraging]] and for locating and identifying potential mates.<ref>{{Cite journal| last1 = Grasso | first1 = F.| last2 = Basil | first2 = J.| title = The evolution of flexible behavioral repertoires in cephalopod molluscs| journal = Brain, Behavior and Evolution| volume = 74| issue = 3| pages = 231–245| year = 2009| pmid = 20029186| doi = 10.1159/000258669| s2cid = 13310728}}</ref>

The "ear" of the nautilus consists of structures called ''[[otocyst]]s'' located immediately behind the pedal [[ganglia]] near the nerve ring. They are oval structures densely packed with elliptical [[calcium carbonate]] crystals.

===Brain and intelligence===
{{Main|Cephalopod intelligence}}
Nautiluses are much closer to the first cephalopods that appeared about 500 million years ago than the early modern cephalopods that appeared maybe 100 million years later ([[ammonoids]] and [[coleoids]]). They have a seemingly simple [[brain]], not the large complex brains of [[octopus]], [[cuttlefish]] and [[squid]], and had long been assumed to lack intelligence. But the cephalopod nervous system is quite different from that of other animals, and recent experiments have shown not only memory, but a changing response to the same event over time.<ref name="callaway">{{cite magazine|url=https://www.newscientist.com/article/dn14033-simpleminded-nautilus-reveals-flash-of-memory.html|title=Simple-Minded Nautilus Shows Flash of Memory|author=Ewen Callaway|date=2 June 2008|magazine=New Scientist|access-date=7 March 2012}}</ref><ref name="phillips">{{cite journal|url=http://jeb.biologists.org/content/211/12/iii.full.pdf#page=1&view=FitH |archive-url=https://web.archive.org/web/20121029181222/http://jeb.biologists.org/content/211/12/iii.full.pdf |archive-date=2012-10-29 |url-status=live|title=Living Fossil Memories|author=Kathryn Phillips|date=15 June 2008|page=iii|volume=211|doi=10.1242/jeb.020370 |journal= Journal of Experimental Biology|issue=12|s2cid=84279320|doi-access=free|bibcode=2008JExpB.211Y...3P }}</ref><ref name="crook"/>

In a study in 2008, a group of nautiluses (''N. pompilius'') were given food as a bright blue light flashed until they began to associate the light with food, extending their tentacles every time the blue light was flashed. The blue light was again flashed without the food 3 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours later. The nautiluses continued to respond excitedly to the blue light for up to 30 minutes after the experiment. An hour later they showed no reaction to the blue light. However, between 6 and 12 hours after the training, they again responded to the blue light, but more tentatively. The researchers concluded that nautiluses had memory capabilities similar to the "[[short-term memory|short-term]]" and "[[long-term memory|long-term memories]]" of the more advanced cephalopods, despite having different brain structures.<ref name="callaway" /><ref name="phillips" /><ref name="crook"/> However, the long-term memory capability of nautiluses was much shorter than that of other cephalopods. The nautiluses completely forgot the earlier training 24 hours later, in contrast to octopuses, for example, which can remember conditioning for weeks afterwards. However, this may be simply the result of the [[classical conditioning|conditioning]] procedure being suboptimal for sustaining long-term memories in nautiluses. Nevertheless, the study showed that scientists had previously underestimated the memory capabilities of nautiluses.<ref name="crook">{{cite journal|author1=Robyn Crook  |author2=Jennifer Basil |name-list-style=amp |year=2008|title=A biphasic memory curve in the chambered nautilus, ''Nautilus pompilius'' L. (Cephalopoda: Nautiloidea) |journal=The Journal of Experimental Biology|volume=211|pages=1992–1998|doi=10.1242/jeb.018531 |url=http://jeb.biologists.org/content/211/12/1992.full.pdf#page=1&view=FitH |archive-url=https://web.archive.org/web/20110817221242/http://jeb.biologists.org/content/211/12/1992.full.pdf |archive-date=2011-08-17 |url-status=live|issue=12 |pmid=18515730|s2cid=6305526 |doi-access=free|bibcode=2008JExpB.211.1992C }}</ref>

===Reproduction and lifespan===
Nautiluses reproduce by laying [[egg (biology)|egg]]s. Gravid females attach the fertilized eggs, either singly or in small batches, to rocks in warmer waters (21–25 Celsius), whereupon the eggs take eight to twelve months to develop until the {{convert|30|mm|adj=on}} juveniles hatch.<ref>{{cite book |last1=Hanlon |first1=Roger T. |last2=Messenger |first2=John B. |title=Cephalopod Behaviour |date=1998 |publisher=Cambridge University Press |location=Cambridge, UK |isbn=9780521645836 |page=178}}</ref> Females spawn once per year and regenerate their [[gonad]]s, making nautiluses the only cephalopods to present [[iteroparity]] or [[polycyclic spawning]].<ref>{{Cite journal | last1 = Rocha | first1 = F. | last2 = Guerra | first2 = Á. | last3 = González | first3 = Á. F. | doi = 10.1017/S1464793101005681 | title = A review of reproductive strategies in cephalopods | journal = Biological Reviews of the Cambridge Philosophical Society | volume = 76 | issue = 3 | pages = 291–304 | year = 2001 | pmid =  11569786| s2cid = 5777682 }}</ref>

Nautiluses are [[sexual dimorphism|sexually dimorphic]], in that males have four tentacles modified into an organ, called the "[[spadix (zoology)|spadix]]", which transfers sperm into the female's mantle during mating. At sexual maturity, the male shell becomes slightly larger than the female's.<ref name="Bruce Saunders1978">{{Cite journal | last1 = Bruce Saunders | first1 = W. | last2 = Spinosa | first2 = C. | title = Sexual Dimorphism in Nautilus from Palau | journal = Paleobiology | volume = 4 | issue = 3 | pages = 349–358 | year = 1978 |jstor=2400210| doi = 10.1017/S0094837300006047 | bibcode = 1978Pbio....4..349S | s2cid = 85899974 }}</ref> Males have been found to greatly outnumber females in practically all published studies, accounting for 60 to 94% of all recorded individuals at different sites.<ref name="Dunstan et al. 2011" />

The lifespan of nautiluses may exceed 20 years, which is exceptionally lengthy for a cephalopod, many of whom live less than three even in captivity and under ideal living conditions.<ref>{{cite journal |author=Saunders WB |title=Nautilus Growth and Longevity: Evidence from Marked and Recaptured Animals |journal=Science |volume=224 |issue=4652 |pages=990–992 |date=June 1984 |pmid=17731999 |doi=10.1126/science.224.4652.990 |bibcode = 1984Sci...224..990S |s2cid=40891271 }}</ref> However, nautiluses typically do not reach sexual maturity until they are about 15 years old, limiting their reproductive lifespan to often less than five years.<ref name="Dunstan et al. 2011">{{cite journal |last1=Dunstan |first1=A.J. |last2=Ward |first2=P.D. |last3=Marshall |first3=N.J. |date=February 2011 |editor1-last=Solan |editor1-first=Martin |title=''Nautilus pompilius'' life history and demographics at the Osprey Reef Seamount, Coral Sea, Australia |journal=PLOS ONE |volume=6 |issue=2 |pages=e16312 |pmid=21347356 |pmc=3037366 |bibcode = 2011PLoSO...616312D |doi=10.1371/journal.pone.0016312 |doi-access=free }}</ref>

''Nautilus'' male has a reproductive organ named [[Van der Hoeven's organ]]. ''Nautilus'' female has two reproductive organs whose functions are unknown, the [[Organ of Valenciennes]] and [[Owen's laminated organ]].<ref name="Willey1902">{{cite book |author=Arthur Willey |url=https://books.google.com/books?id=Jwo4AQAAMAAJ&pg=PA778 |title=Zoological Results Based on Material from New Britain, New Guinea, Loyalty Islands and Elsewhere: The anatomy and development of Peripatus novae-britanniae |publisher=University Press |year=1902 |pages=778–9}}</ref>

{{multiple image
| align = center
| footer = '''Left:''' Frequency distribution of ''N. pompilius'' shell diameter at [[Osprey Reef]], part of the [[Coral Sea Islands]], based on  2067 captured individuals. Shells ranged in size from 76 to 145&nbsp;mm, with a mean of 128.6±28.01&nbsp;mm.<ref name="Dunstan et al. 2011" /><br/>
'''Right:''' Shell diameter of mature male and female ''N.&nbsp;pompilius'' caught at Osprey Reef. Males (''n'' = 870) had a mean shell diameter of 131.9±2.6&nbsp;mm, compared to 118.9±7.5&nbsp;mm in females (''n'' = 86). The Osprey Reef ''N.&nbsp;pompilius'' population is the second smallest known in terms of mean shell diameter, after the dwarf form from the [[Sulu Sea]] (130.7&nbsp;mm and 115.6&nbsp;mm, respectively).<ref name="Dunstan et al. 2011" />
| image1 = Size frequency distribution for Nautilus pompilius at Osprey Reef.png
| image2 = Sexual dimorphism in mature male and female Nautilus pompilius.png
| direction = 
| total_width = 660
| alt1 = 
| caption1 = 
| caption2 = 
}}

==Ecology==

===Range and habitat===
[[File:Comparison of Nautilus capture rates with trapping depth.png|thumb|upright=1.5|Number of captured ''N.&nbsp;pompilius'' at various depths around the Osprey Reef Seamount, [[Coral Sea]]. The data was collated from 271 trapping events spread across all months of the year. Nautiluses were most common at {{cvt|300|-|350|m|ft|-2}}. No specimens were recovered from a depth of less than {{cvt|150|m|ft|-2}} during 18 trapping efforts.<ref name="Dunstan et al. 2011" />]]
Nautiluses are found only in the [[Indo-Pacific]], from 30° N to 30° S latitude and 90° E to 175° E longitude. They inhabit the deep slopes of [[coral reef]]s.

Nautiluses usually inhabit depths of several hundred metres. It has long been believed that nautiluses rise at night to feed, mate, and lay [[Egg (biology)|eggs]], but it appears that, in at least some populations, the vertical movement patterns of these animals are far more complex.<ref name=vertical>{{Cite journal | last1 = Dunstan | first1 = A. J. | last2 = Ward | first2 = P. D. | last3 = Marshall | first3 = N. J. | editor1-last = Solan | editor1-first = Martin | title = Vertical distribution and migration patterns of ''Nautilus pompilius''| doi = 10.1371/journal.pone.0016311 | journal = [[PLOS ONE]] | volume = 6 | issue = 2 | pages = e16311 | year = 2011 | pmid =  21364981| pmc =3043052 | bibcode = 2011PLoSO...616311D | doi-access = free }}</ref> The greatest depth at which a nautilus has been sighted is {{cvt|703|m|ft}} (''N.&nbsp;pompilius'').<ref name=vertical /> Implosion depth for nautilus shells is thought to be around {{cvt|800|m|ft|-2}}.<ref name="Dunstan et al. 2011" /><ref name=vertical /> Only in [[New Caledonia]], the [[Loyalty Islands]], and [[Vanuatu]] can nautiluses be observed in very shallow water, at depths of as little as {{cvt|5|m|ft|round=5}}.<ref name=Ward1987 /><ref name=vertical /> This is due to the cooler surface waters found in these southern hemisphere habitats as compared to the many equatorial habitats of other nautilus populations – these usually being restricted to depths greater than {{cvt|100|m|ft|-2}}.<ref name=Ward1987 /><ref name=vertical /> Nautiluses generally avoid water temperatures above {{cvt|25|°C|round=5}}.<ref name=vertical />

While nautiloids were once common worldwide, their numbers declined and their distribution became restricted to their current habitats during the Pleistocene, largely due to the diversification of pinnipeds.<ref>{{Cite journal |last=Kiel |first=Steffen |last2=Goedert |first2=James L. |last3=Tsai |first3=Cheng-Hsiu |date=2022 |title=Seals, whales and the Cenozoic decline of nautiloid cephalopods |url=https://onlinelibrary.wiley.com/doi/10.1111/jbi.14488 |journal=Journal of Biogeography |language=en |volume=49 |issue=11 |pages=1903–1910 |doi=10.1111/jbi.14488 |issn=1365-2699}}</ref>

[[File:Deepest record of Nautilus – 703 meters.png|thumb|left|A pair of ''N.&nbsp;pompilius'' feeding on [[two-spot red snapper]] (''Lutjanus bohar'') bait during daytime at {{cvt|703|m|ft}} depth. This observation constitutes the deepest record of any nautilus species.]]

===Diet===
Nautiluses are scavengers and opportunistic predators.<ref>{{Cite journal | last1 = Saunders | first1 = W.B. | title = The role and status of ''Nautilus'' in its natural habitat: Evidence from deep-water remote camera photosequences | journal = Paleobiology | volume = 10 | issue = 4 | pages = 469–486 | doi =  10.1017/S0094837300008472| year = 1984 | jstor = 2400618| bibcode = 1984Pbio...10..469S | s2cid = 87096394 }}</ref><ref>{{Cite journal | last1 = Wells | first1 = M. J. | last2 = Wells | first2 = J. | last3 = O'Dor | first3 = R. K. | doi = 10.1017/S0025315400037723 | title = Life at low oxygen tensions: The behaviour and physiology of ''Nautilus pompilius'' and the biology of extinct forms | journal = Journal of the Marine Biological Association of the United Kingdom | volume = 72 | issue = 2 | pages = 313–328 | year = 2009 | s2cid = 85601385 }}</ref> They eat [[lobster]] [[molt]]s, [[hermit crab]]s, and [[carrion]] of any kind.<ref name=Ward1987>{{cite book |last1= Ward |first1= P.D. |year= 1987 |title= The Natural History of Nautilus |location= London, United Kingdom |publisher= Allen and Unwin |isbn=9780045000364 }}</ref>

==Evolutionary history==
[[File:Allonautilus vs Nautilus.png|thumb|Shell characters of the genera ''Nautilus'' and ''Allonautilus'']]
[[File:Section cut Nautilus.jpg|thumb|Section cut of a nautilus shell]]
[[Fossil]] records indicate that nautiloids have experienced minimal morphological changes over the past 500 million years. Many were initially straight-shelled, as in the extinct genus ''[[Lituites]]''. They developed in the Late [[Cambrian]] period and became a significant group of sea [[predator]]s during the [[Ordovician]] period. Certain species reached over {{cvt|2.5|m|ft|0}} in size. The other cephalopod subclass, [[Coleoidea]], diverged from the nautiloids long ago and the nautilus has remained relatively unchanged since. Nautiloids were much more extensive and varied 200 million years ago. The ancestors of all [[Coleoidea]] (shell-less Cephalopods) once possessed shells, and many early cephalopod [[species]] are only known from shell remains. Following the [[K-Pg extinction event]] most [[nautiloid]] species went [[extinct]], while members of Coleoidea managed to survive. Following the mass extinction, the nautilus became the only extant species of nautiloids.<ref>{{Cite journal|url=https://www.academia.edu/93538950|title=Comparative morphology among representatives of main taxa of Scaphopoda and basal protobranch Bivalvia (Mollusca)|first=Luiz Ricardo L.|last=Simone|date=January 25, 2009|journal=Papéis Avulsos de Zoologia|volume=49|issue=32|pages=405–457|doi=10.1590/S0031-10492009003200001 |via=www.academia.edu|doi-access=free}}</ref><ref>{{Cite journal|url=https://sjpp.springeropen.com/articles/10.1007/s13358-016-0112-7|title=Nautilus: biology, systematics, and paleobiology as viewed from 2015|first1=Peter|last1=Ward|first2=Frederick|last2=Dooley|first3=Gregory Jeff|last3=Barord|date=March 25, 2016|journal=[[Swiss Journal of Palaeontology]]|volume=135|issue=1|pages=169–185|via=sjpp.springeropen.com|doi=10.1007/s13358-016-0112-7|bibcode=2016SwJP..135..169W |s2cid=87025055 |url-access=subscription}}</ref>

The family Nautilidae has its origin in the [[Trigonocerataceae]] ([[Centroceratina]]), specifically in the [[Syringonautilidae]] of the [[Late Triassic]]<ref name=Kummel /> and continues to this day with ''[[Nautilus (genus)|Nautilus]]'', the type genus, and its close relative, ''[[Allonautilus]]''.

===Fossil genera===
[[File:Eutrephoceras dorbignyanum (Forbes in Darwin, 1846) - Santiago specimen.jpg|thumb|''[[Eutrephoceras|Eutrephoceras dorbignyanum]]'']]
The fossil record of Nautilidae begins with ''[[Cenoceras]]'' in the Late Triassic, a highly varied genus that makes up the [[Jurassic]] ''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]] and is followed by the [[Upper Jurassic]]-[[Miocene]] ''[[Eutrephoceras]]''.

''[[Eutrephoceras]]'' is generally subglobular, 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]] 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]] and in [[Libya]].

''[[Carinonautilus]]'' is a genus from the [[Upper Cretaceous]] of [[India]], 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.

''[[Obinautilus]]'' has also been placed in Nautilidae by some authorities, though it may instead be an [[Argonautidae|argonautid]] [[octopus]].<ref>Teichert, C. & T. Matsumoto (2010). The Ancestry of the Genus ''Nautilus''. In: W.B. Saunders & N.H. Landman (eds.) ''Nautilus: The Biology and Paleobiology of a Living Fossil''. Springer. pp.&nbsp;25–32. {{doi|10.1007/978-90-481-3299-7_2}}</ref><ref name=LA>{{cite journal | last1 = Saul | first1 = L.R. | last2 = Stadum | first2 = C.J. | year = 2005 | title = Fossil argonauts (Mollusca: Cephalopoda: Octopodida) from Late Miocene siltstones of the Los Angeles Basin, California | journal = Journal of Paleontology | volume = 79 | issue = 3| pages = 520–531 | doi = 10.1666/0022-3360(2005)079<0520:FAMCOF>2.0.CO;2 | bibcode = 2005JPal...79..520S | s2cid = 131373540 }}</ref>

==Taxonomy==
[[Image:Nautilus species shells.png|thumb|upright=1.35|right |Nautilus shells: Left: ''Nautilus pompilius''; center: ''Allonautilus scrobiculatus''; right: ''Nautilus macromphalus''.|alt=Photo of profiles of three progressively larger nautilus shells]]
The family Nautilidae contains up to nine [[Extant taxon|extant]] species and several [[extinct species]]:<ref name="GoedertEtAl">{{Cite journal|title = Miocene ''Nautilus'' (Mollusca, Cephalopoda) from Taiwan, and a review of the Indo-Pacific fossil record of ''Nautilus''| date=2022 | doi=10.1111/iar.12442 | last1=Goedert | first1=James L. | last2=Kiel | first2=Steffen | last3=Tsai | first3=Cheng-Hsiu | journal=Island Arc | volume=31 | issue=1 | s2cid=247532223 | doi-access=free | bibcode=2022IsArc..31E2442G }}</ref>

*Genus '''''[[Allonautilus]]'''''
**''[[Allonautilus perforatus|A. perforatus]]''
**''[[Crusty Nautilus|A. scrobiculatus]]''
*Genus '''''[[Nautilus (genus)|Nautilus]]'''''
**†''[[Nautilus altifrons|N. altifrons]]''
**†''[[Nautilus balcombensis|N. balcombensis]]''
**''[[Nautilus belauensis|N. belauensis]]''
**†''[[Nautilus butonensis|N. butonensis]]''
**†''[[Nautilus campbelli|N. campbelli]]''
**†''[[Nautilus cookanus|N. cookanus]]''
**†''[[Nautilus geelongensis|N. geelongensis]]''
**†''[[Nautilus javanus|N. javanus]]''
**''[[Nautilus macromphalus|N. macromphalus]]''
**''[[Nautilus pompilius|N. pompilius]]'' ([[type species|type]])
***''N. p. pompilius''
***''N. p. suluensis''
**†''[[Nautilus praepompilius|N. praepompilius]]''
** ''[[Nautilus samoaensis]]'' <small>Barord ''et al.'', 2023</small><ref name="Barord 2023">Gregory J. Barord, David J. Combosch, Gonzalo Giribet, Neil Landman, Sarah Lemer, Job Veloso et Peter D. Ward, «&nbsp;[https://zookeys.pensoft.net/article/84427/ Three new species of ''Nautilus'' Linnaeus, 1758 (Mollusca, Cephalopoda) from the Coral Sea and South Pacific]&nbsp;», ''ZooKeys'', vol.&nbsp;1143, 2023, p.&nbsp;51-69.</ref> – Samoa
**''[[Nautilus stenomphalus|N. stenomphalus]]''
**†''[[Nautilus taiwanus]]'' <small>Huang, 2002</small>– Taiwan
**''[[Nautilus vanuatuensis]]'' <small>Barord ''et al.'', 2023</small><ref name="Barord 2023"/> – Vanuatu
**''[[Nautilus vitiensis]]'' <small>Barord ''et al.'', 2023</small><ref name="Barord 2023"/> – Fiji

Genetic data collected in 2011 pointed to there being only three extant species: ''A. scrobiculatus'', ''N. macromphalus'', and ''N. pompilius'', with ''N. belauensis'' and ''N. stenomphalus'' both subsumed under ''N. pompilius'', possibly as [[subspecies]],<ref name="Dunstan et al. 2011" /> though this was prior to the description of three additional species (''samoaensis'', ''vanuatuensis'' and ''vitiensis'').

===Dubious or uncertain taxa===
The following [[taxon|taxa]] associated with the family Nautilidae are of uncertain taxonomic status:<ref>Sweeney, M.J. 2002. [http://tolweb.org/accessory/Nautilidae_Taxa?acc_id=2324 Taxa Associated with the Family Nautilidae Blainville, 1825.] Tree of Life web project.</ref>

{| class="wikitable sortable" style="width: 100%; text-align: left;"
|-
! Binomial name and author citation !! Current systematic status !! Type locality !! Type repository
|-
| ''N. alumnus'' [[Tom Iredale|Iredale]], 1944 ||[[Nomen dubium|Species dubium]] [''fide'' Saunders (1987:49)] ||[[Queensland]], [[Australia]] ||  Not designated [''fide'' Saunders (1987:49)]
|-
| ''N. ambiguus'' Sowerby, 1848 || Species dubium [''fide'' Saunders (1987:48)] || Not designated || Unresolved
|-
| ''N. beccarii'' [[Carl Linnaeus|Linné]], 1758 || Non-cephalopod; [[Foraminifera]] [''fide'' Frizzell and Keen (1949:106)] || || 
|-
| ''N. calcar'' Linné, 1758 || ?Non-cephalopod; Foraminifera Lenticulina || [[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. crispus'' Linné, 1758 || Undetermined || [[Mediterranean Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. crista'' Linné, 1758 || Non-cephalopod; ''[[Turbo (genus)|Turbo]]'' [''fide'' Dodge (1953:14)] || || 
|-
| ''N. fascia'' Linné, 1758 || Undetermined || [[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. granum'' Linné, 1758 || Undetermined || [[Mediterranean Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. lacustris'' [[John Lightfoot FRS|Lightfoot]], 1786 || Non-cephalopod; ''[[Helix (genus)|Helix]]'' [''fide'' [[Lewis Weston Dillwyn|Dillwyn]] (1817:339)] || || 
|-
| ''N. legumen'' Linné, 1758 || Undetermined || [[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. micrombilicatus'' [[Louis Joubin|Joubin]], 1888 ||''[[Nomen nudum]]'' || ||
|-
| ''N. obliquus'' Linné, 1758 || Undetermined || [[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. pompilius marginalis'' Willey, 1896 || Species dubium [''fide'' Saunders (1987:50)] || [[New Guinea]] || Unresolved
|-
| ''N. pompilius moretoni'' Willey, 1896 || Species dubium [''fide'' Saunders (1987:49)] || [[New Guinea]] || Unresolved
|-
| ''N. pompilius perforatus'' Willey, 1896 || Species dubium [''fide'' Saunders (1987:49)] || [[New Guinea]] || Unresolved
|-
| ''N. radicula'' Linné, 1758 || ?Non-cephalopod; F. Nodosaria ||[[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. raphanistrum'' Linné, 1758 || Undetermined || [[Mediterranean Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. raphanus'' Linné, 1758 || Undetermined || [[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. semi-lituus'' Linné, 1758 || Undetermined || [[Liburni]], [[Adriatic Sea]] || Unresolved; [[Linnean Society of London]]?
|-
| ''N. sipunculus'' Linné, 1758 || Undetermined || "freto Siculo" || Unresolved; [[Linnean Society of London]]?
|-
| ''N. texturatus'' Gould, 1857 || ''Nomen nudum'' || ||
|-
| ''Octopodia nautilus'' Schneider, 1784 || Rejected specific name [''fide'' Opinion 233, ICZN (1954:278)] || ||
|}

==  Conservation status and human use ==
Nautilus are collected or fished for sale as live animals or to carve the shells for souvenirs and collectibles, not for just the shape of their shells, but also the nacreous inner shell layer, which is used as a [[pearl]] substitute.<ref name="RBoZ">{{Cite journal |last1=Nijman |first1=Vincent |last2=Lee |first2=Paige Biqi |date=December 2016 |title=Trade in nautilus and other large marine molluscs as ornaments and decorations in Bali, Indonesia |url=https://www.researchgate.net/publication/311466511 |journal= Raffles Bulletin of Zoology |volume=64 |pages=368–373 |via= ResearchGate}}</ref><ref>{{Cite journal|last=De Angelis |first=Patricia |year=2012 |title=Assessing the impact of international trade on chambered nautilus|journal=Geobios |volume=45 |issue=1 |pages=5–11 |via=Elsevier Science Direct |doi=10.1016/j.geobios.2011.11.005 |bibcode=2012Geobi..45....5D }}</ref><ref>{{Cite journal |last1=Freitas |first1=B. |last2=Krishnasamy |first2=K. |title=An Investigation into the Trade of Nautilus |url=https://www.traffic.org/publications/reports/an-investigation-into-the-trade-of-nautilus/ |year=2016 |location=Washington DC, USA |journal=TRAFFIC Report |publisher=TRAFFIC Network / World Wildlife Fund }}</ref> In [[Samoa]], nautilus shells decorate the forehead band of a traditional headdress called [[Culture of Samoa#Dress|''tuiga'']].<ref>{{Cite web |title=Tuiga: a Samoan ceremonial headdress |publisher=Museum of New Zealand |url=https://collections.tepapa.govt.nz/topic/10595 |access-date=Aug 23, 2023 }}</ref> Nautilus shells were popular items in the [[Renaissance]] and [[Baroque]] [[cabinet of curiosities]] and were often mounted by [[goldsmith]]s on a thin stem to make extravagant [[nautilus shell cups]].

The low [[fecundity]], late maturity, long gestation period and long life-span of nautiluses suggest that these species are vulnerable to overexploitation and demand for the ornamental shell is causing population declines.<ref>{{Cite journal|last1=Dunstan|first1=Andrew|last2=Bradshaw|first2=Corey J. A.|last3=Marshall|first3=Justin|date=2011-02-10|title=Nautilus at risk – Estimating population size and demography of ''Nautilus pompilius''|journal=PLOS ONE|volume=6|issue=2|doi=10.1371/journal.pone.0016716|issn=1932-6203|pmc=3037370|pmid=21347360|page=e16716|bibcode=2011PLoSO...616716D|doi-access=free}}</ref> The threats from trade in these shells has led to countries such as Indonesia legally protecting the chambered nautilus with fines of up to US$8,500 and/or 5 years in prison for trading in this species. Despite their legal protection, these shells were reported to be openly sold at tourist areas in Bali as of 2014.<ref name="RBoZ" /> The continued trade of these animals has led to a call for increased protection<ref>{{cite web|url=https://blogs.scientificamerican.com/extinction-countdown/nautilus-protection/|title=Nautilus Finally Moves toward Endangered Species Protection|last=Platt|first=John|website=Scientific American}}</ref> and in 2016 all species in Family Nautilidae<ref name="cites">{{cite web|url=https://cites.org/sites/default/files/eng/cop/17/prop/060216/E-CoP17-Prop-48%20Rev.pdf |archive-url=https://web.archive.org/web/20170118111839/https://cites.org/sites/default/files/eng/cop/17/prop/060216/E-CoP17-Prop-48%20Rev.pdf |archive-date=2017-01-18 |url-status=live|title=Inclusion of the Family Nautilidae|author1=Fiji|author2=India|author3=Palau|author4=the United States of America|year=2016|publisher=CITES|quote=because  all  species  are  being  proposed  for  listing,  this  proposal  seeks  to  list  the Family Nautilidae in Appendix II.}}</ref> were added to [[CITES Appendix II]], regulating international trade.<ref>{{cite web|url=https://www.fws.gov/le/pdf/12-21-2016-COP-17-Changes.pdf |archive-url=https://web.archive.org/web/20161228203239/https://www.fws.gov/le/pdf/12-21-2016-COP-17-Changes.pdf |archive-date=2016-12-28 |url-status=live|title=Notice to the Wildlife Import/Export Community}}</ref><ref name="sa">{{cite magazine|url=https://blogs.scientificamerican.com/extinction-countdown/cites-cop17-wrapup/|title=Great News for Rhinos, Pangolins, Parrots, Sharks and Chambered Nautilus|last=Platt|first=John R.|date=2016-10-05|magazine=Scientific American|access-date=2017-01-15|quote=The chambered nautilus—victim of intense overharvesting for their beautiful shells—has been added to CITES Appendix II, which means all trade will now take place under a permit system, allowing the industry to be monitored for sustainability.}}</ref>

<gallery widths="200px" heights="200px">
File:Berlín KGM nautilus.JPG|Baroque ''nautilus cup'' of Aleksander Kęsowski, abbot of [[Oliwa]], 1643–1667<ref name=artinpl/>
File:Nautilus shell carved and painted C19th Poldi Pezzoli Museum.jpg|Nautilus shell carved and painted with fanciful scenes of human figures and animals (spider, dragonfly, dog, butterfly, sawfly, fly), bronze pendant mount, nineteenth century. [[Museo Poldi Pezzoli|Poldi Pezzoli Museum]], Milan
File:Nautilus cup in the form of a chicken.jpg|A nautilus shell in the form of a chicken, circa 1550
</gallery>

==In human culture==
[[Palau]]ans see nautili ({{langx|pau|kedarm}}) as a symbol of vulnerable or fragile character from a belief that they easily die even from slight bumps on ocean rocks; hence someone who gets quickly angry after being pranked is compared to one ({{lang|pau|ng ko er a kedarm, el di metirem e metord}}<!--spelling from New Palauan-English Dictionary [1990]-->).<ref>{{cite journal |title=Proverbs of Palau |first1=Robert K. |last1=McKnight |journal=The Journal of American Folklore |date=1968 |volume=81 |issue=319 |pages=22 |doi=10.2307/537435|jstor=537435 }}</ref>

==See also==

* [[Cephalopod size]], for maximum shell diameters
* ''[[Historia animalium (Gessner book)|Historia animalium]]'' by [[Conrad Gessner]], first book with fossil illustrations
* ''[[The Nautilus (journal)|The Nautilus]]'', a malacological journal
* [[Chambered Nautilus#In literature and art|''The Chambered Nautilus'']], a poem of [[Oliver Wendell Holmes Sr.|Oliver Wendell Holmes]]
*[[Nautilus Pompilius (band)|Nautilus Pompilius]], a Russian rock band
*[[Nautilus (fictional submarine)|''Nautilus'' (fictional submarine)]] from [[Jules Verne]]’s classic 1870 science-fiction novel ''[[Twenty Thousand Leagues Under the Seas]]'', describing the voyage of [[Captain Nemo]]’s ''Nautilus'' submarine.

==Notes==
{{notelist}}

==References==
{{Reflist|colwidth=30em|refs=
<ref name=artinpl>{{cite web|author=Marcin Latka |title= Abbot Kęsowski's cup |url=https://artinpoland.weebly.com/en/abbot-kesowskis-cup |work=artinpl |access-date=26 July 2019}}</ref>}}

== Bibliography ==
* Ward, P.D. 1988. ''In Search of Nautilus''. Simon and Schuster.
* {{Cite book | title = Nautilus: the biology and palaeontology of a living fossil |author1=W. Bruce Saunders  |author2=Neil H. Landman  |name-list-style=amp |series=Topics in Geobiology |volume=6 |year=2010 | isbn = 978-90-481-3299-7 |location=Dordrecht |publisher=Springer Science+Business Media B.V | doi = 10.1007/978-90-481-3299-7 |s2cid=237330597 }}
{{CephBase Family|Nautilidae}}

==External links==
* [https://www.tonmo.com/community/forums/nautilidae.58/ Nautilidae discussion forum], tonmo.com
* [https://web.archive.org/web/20060924223738/http://www.waquarium.org/MLP/root/pdf/MarineLife/Invertebrates/Molluscs/Nautilus.pdf Waikïkï Aquarium: Marine Life Profile: Chambered Nautilus], waguarium.org
* [https://web.archive.org/web/20050426132101/http://www.cephbase.utmb.edu/refdb/pdf/8036.pdf A molecular and karyological approach to the taxonomy of ''Nautilus''], utmb.edu

{{Edible molluscs}}
{{Taxonbar|from=Q223939}}
{{Authority control}}

[[Category:Nautiluses| ]]
[[Category:Articles containing video clips]]
[[Category:Extant Triassic first appearances]]