Editing Platypus

{{Short description|Species of mammal}}
{{Other uses}}
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{{Use Australian English|date=February 2012}}
{{Use dmy dates|date=September 2024}}
{{Speciesbox
| fossil_range = {{Fossil range/linked|Pliocene|Recent}}
| image = Duck-billed platypus (Ornithorhynchus anatinus) Scottsdale.jpg
| image_caption = Platypus swimming in waters near [[Scottsdale, Tasmania]]
| status = NT
| status_system = IUCN3.1
| status_ref = <ref name="iucn">{{cite iucn |author=Woinarski, J. |author2=Burbidge, A.A. |date=2016 |title=''Ornithorhynchus anatinus'' |volume=2016 |page=e.T40488A21964009 |doi=10.2305/IUCN.UK.2016-1.RLTS.T40488A21964009.en |access-date=19 November 2021}}</ref>
| taxon = Ornithorhynchus anatinus
| parent_authority = [[Johann Friedrich Blumenbach|Blumenbach]], 1800
| authority = ([[George Shaw (biologist)|Shaw]], 1799)
| synonyms = {{Species list
|''Platypus anatinus''| Shaw, 1799
|''Ornithorhynchus paradoxus''| Blumenbach, 1800
|''O. novaehollandiae''| [[Bernard Germain de Lacépède|Lacépède]], 1800
|''O. fuscus''| [[François Péron|Péron]], 1807
|''O. rufus''| Péron, 1807
|''O. paradoxi''| [[Johann Friedrich Meckel|Meckel]], 1826
|''O. crispus''| [[William MacGillivray|MacGillivray]], 1827
|''O. laevis''| MacGillivray, 1827
|''O. brevirostris''| [[William Ogilby|Ogilby]], 1832
|''O. agilis''| [[Charles Walter De Vis|de Vis]], 1886
|''O. phoxinus'' | [[Oldfield Thomas|O. Thomas]], 1923
|''O. triton'' | O. Thomas, 1923
}}
| synonyms_ref = <ref>{{GBIF |id=2433376 |taxon=''Ornithorhynchus anatinus'' |access-date=13 July 2021}}</ref><ref>{{cite journal |last1=Pasitschniak-Arts |first1=Maria |last2=Marinelli |first2=Lui |title=Ornithorhynchus anatinus |journal=Mammalian Species |date=1 June 1998 |issue=585 |pages=1–9 |doi=10.2307/3504433 |jstor=3504433 |url=https://academic.oup.com/mspecies/article/doi/10.2307/3504433/2600754 |access-date=15 October 2024}}</ref>
| range_map = Distribution of the Platypus (Ornithorhynchus anatinus).png
| range_map_caption = Platypus range{{break}}(red – native, yellow – introduced)
}}

The '''platypus''' ('''''Ornithorhynchus anatinus'''''), sometimes referred to as the '''duck-billed platypus''', is a [[semiaquatic]], egg-laying [[mammal]] endemic to [[Eastern states of Australia|eastern Australia]], including [[Tasmania]]. The platypus is the sole living representative or [[monotypic taxon]] of its [[Family (biology)|family]] [[Ornithorhynchidae]] and [[genus]] '''''Ornithorhynchus''''', though a number of [[Fossil Monotremes|related species]] appear in the fossil record.

Together with the four species of [[echidna]], it is one of the five [[wikt:extant|extant]] species of [[monotreme]]s, mammals that lay [[Egg (biology)|eggs]] instead of giving birth to live young. Like other monotremes, the platypus has a sense of [[electroreception|electrolocation]], which it uses to detect prey in cloudy water. It is one of the few species of [[venomous mammals]], as the male platypus has a [[spur (zoology)|spur]] on the hind foot that delivers an extremely painful [[Platypus venom|venom]].

The unusual appearance of this egg-laying, [[duck]]-billed, [[beaver]]-tailed, [[otter]]-footed mammal at first baffled European naturalists. In 1799, the first scientists to examine a preserved platypus body judged it a fake made of several animals sewn together.

The unique features of the platypus make it important in the study of [[evolutionary biology]], and a recognisable and iconic symbol of [[Australia]]. It is culturally significant to several [[Aboriginal Australians|Aboriginal peoples]], who also used to hunt it for food. It has appeared as a national mascot, features on the [[Obverse and reverse|reverse]] of the [[Australian twenty-cent coin]], and is an emblem of the state of [[New South Wales]].

The platypus was hunted for its fur, but it has been a legally [[protected species]] in all states where it occurs since 1912. Its population is not under severe threat, although [[captive breeding|captive-breeding]] programs have had slight success, and it is vulnerable to pollution. It is classified as a [[near-threatened species]] by the [[IUCN]], but a November 2020 report has recommended that it be upgraded to [[threatened species]] under the federal ''[[EPBC Act]]'', due to [[habitat destruction]] and declining numbers in all states.

== Taxonomy and naming ==
{{See also|Plural form of words ending in -us#Platypus}}

[[Australian Aboriginal people]] name or have named the platypus in various ways depending on [[Australian Aboriginal languages|Australian indigenous languages and dialects]]. Among the names found: ''boondaburra'', ''mallingong'', ''tambreet'', ''watjarang''<ref>{{cite web|access-date=2024-10-03 |date=2024-03-06 |language=en-US |title=Platypus names (including "What's the plural of platypus?") - Australian Platypus Conservancy |url=https://platypus.asn.au/platypus-names-including-whats-the-plural-of-platypus/ |website=platypus.asn.au}}<!-- auto-translated from French by Module:CS1 translator --></ref> (names in [[Yass, New South Wales|Yass]], [[Murrumbidgee Shire|Murrumbidgee]], and [[Tumut]]),<ref name=":2" /> ''tohunbuck'' (region of [[Goomburra]], [[Darling Downs]]),<ref name=":2">{{cite web|access-date=2024-10-03 |language=en-US |title=Platypus {{!}} Wildlife Preservation Society of Queensland |url=https://wildlife.org.au/news-resources/educational-resources/species-profiles/mammals/platypus/}}<!-- auto-translated from French by Module:CS1 translator --></ref> ''dulaiwarrung''<ref>{{cite book|author1=M. Serena & G.A. Williams |date=2010 |publisher=Australian Platypus Conservancy |title=Conserving platypus and rat waters |url=https://www.tweed.nsw.gov.au/files/assets/public/v/1/documents/environment/waterways-amp-coastline/conserving-platypus-information-and-guidelines.pdf}}<!-- auto-translated from French by Module:CS1 translator --></ref> or ''dulai warrung'' ([[Woiwurrung–Taungurung language|Woiwurrung]] language, [[Wurundjeri]], [[Victoria (State)|Victoria]]),<ref name=":1">{{cite web|access-date=2024-10-03 |language=en |title=Platypus- WWF-Australia {{!}} Platypus {{!}} WWF Australia |url=https://wwf.org.au/what-we-do/species/platypus/ |website=wwf.org.au}}<!-- auto-translated from French by Module:CS1 translator --></ref> ''djanbang'' ([[Yugambeh–Bundjalung languages|Bundjalung]], [[Queensland]]),<ref>{{cite web|access-date=2024-10-03 |language=en |title=Platypus- WWF-Australia {{!}} Platypus {{!}} WWF Australia |url=https://wwf.org.au/what-we-do/species/platypus/ |website=wwf.org.au}}<!-- auto-translated from French by Module:CS1 translator --></ref> ''djumulung'' ([[Yuin–Kuric languages|Yuin]] language, [[Yuin]], [[New South Wales]]),<ref>{{cite web|access-date=2024-10-03 |language=en |title=Platypus- WWF-Australia {{!}} Platypus {{!}} WWF Australia |url=https://wwf.org.au/what-we-do/species/platypus/ |website=wwf.org.au}}<!-- auto-translated from French by Module:CS1 translator --></ref> ''maluŋgaŋ'' (ngunnawal language, [[Ngunnawal]], [[Australian Capital Territory]]<ref>{{cite web|access-date=2024-10-03 |language=en |title=Platypus- WWF-Australia {{!}} Platypus {{!}} WWF Australia |url=https://wwf.org.au/what-we-do/species/platypus/ |website=wwf.org.au}}<!-- auto-translated from French by Module:CS1 translator --></ref>), ''biladurang'', ''wamul'', ''dyiimalung'', ''oornie'', ''dungidany'' ([[Wiradjuri language|Wiradjuri]] language, [[Wiradjuri]], [[Victoria (State)|Vic]], [[New South Wales|NSW]]),<ref name=":1" /> ''oonah'',<ref>{{cite web | url=https://steemit.com/animals/@mostly.nature/platypus-out-of-the-water | title=Platypus Out of the Water | date=3 July 2017 }}</ref> etc. The name chosen and approved in [[Palawa kani]] (reconstructed [[Tasmanian languages|Tasmanian]] language) is ''larila''.<ref>{{cite web|access-date=2024-10-03 |language=en-AU |title=Larila's Legacy |url=https://hobartrivuletplatypus.org/larilas-legacy/ |website=Hobart Rivulet Platypus}}<!-- auto-translated from French by Module:CS1 translator --></ref>

When the platypus was first encountered by Europeans in 1798, a [[Pelage|pelt]] and sketch were sent back to [[Kingdom of Great Britain|Great Britain]] by [[John Hunter (Royal Navy officer)|Captain John Hunter]], the second Governor of [[New South Wales]].<ref name="Paradox">{{cite journal|journal=BioScience|jstor=1313511|title=The Paradoxical Platypus|first=Brian K. |last=Hall|volume=49|issue=3|pages=211–8|date=March 1999|doi=10.2307/1313511|doi-access=free}}</ref> British scientists' initial hunch was that the attributes were a hoax.<ref name="hoax">{{cite web|url=http://www.museumofhoaxes.com/hoax/archive/permalink/the_duckbilled_platypus|title=Duck-billed Platypus|publisher=Museum of hoaxes|access-date=21 July 2010|archive-date=29 July 2014|archive-url=https://web.archive.org/web/20140729074144/http://www.museumofhoaxes.com/hoax/archive/permalink/the_duckbilled_platypus|url-status=live}}</ref> [[George Shaw (biologist)|George Shaw]], who produced the first description of the animal in the ''Naturalist's Miscellany'' in 1799, stated it was impossible not to entertain doubts as to its genuine nature,<ref name="Shaw-1799">{{cite journal |last1=Shaw |first1=George |last2=Nodder |first2=Frederick Polydore |title=The Duck-Billed Platypus, ''Platypus anatinus'' |journal=The Naturalist's Miscellany |year=1799 |volume=10 |issue=CXVIII |pages=385–386 |doi=10.5962/p.304567 |url=https://www.biodiversitylibrary.org/part/304567 }}</ref> and [[Robert Knox (surgeon)|Robert Knox]] believed it might have been produced by some Asian [[Taxidermy|taxidermist]].<ref name="hoax"/> It was thought somebody had sewn a duck's beak onto the body of a beaver-like animal. Shaw even took a pair of scissors to the dried skin to check for stitches.<ref name="APC">{{cite web|url=http://www.platypus.asn.au/|title=Platypus facts file|publisher=Australian Platypus Conservancy|access-date=13 September 2006|archive-date=10 November 2015|archive-url=https://web.archive.org/web/20151110113935/http://www.platypus.asn.au/|url-status=live}}</ref><ref name="Shaw-1799" />

The common name "platypus" literally means 'flat-foot', deriving from the [[Ancient Greek|Greek]] word {{transliteration|grc|platúpous}} ({{wikt-lang|grc|πλατύπους}}),<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dplatu%2Fpous πλατύπους] {{Webarchive|url=https://web.archive.org/web/20210225004134/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dplatu%2Fpous |date=25 February 2021 }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> from {{transliteration|grc|platús}} ({{wikt-lang|grc|πλατύς}} 'broad, wide, flat')<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dplatu%2Fs πλατύς] {{Webarchive|url=https://web.archive.org/web/20210225083230/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dplatu%2Fs |date=25 February 2021 }}, ''A Greek-English Lexicon'', on Perseus</ref>{{efn|The same root gives rise to [[platysma]], a broad, wide and flat muscle of the neck.}} and {{transliteration|grc|poús}} ({{wikt-lang|grc|πούς}} 'foot').<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dpou%2Fs πούς] {{Webarchive|url=https://web.archive.org/web/20210227054504/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dpou%2Fs |date=27 February 2021 }}, ''A Greek-English Lexicon'', on Perseus</ref><ref>{{cite book|author1=Liddell, Henry George|author2=Scott, Robert|name-list-style=amp|year=1980|title=Greek-English Lexicon, Abridged Edition|publisher=Oxford University Press, Oxford, UK|isbn=978-0-19-910207-5|url-access=registration|url=https://archive.org/details/lexicon00lidd}}</ref> Shaw initially assigned the species the [[Linnaean taxonomy|Linnaean]] name ''Platypus anatinus'' when he described it,<ref name="Shaw-1799"/> but the genus term was quickly discovered to already be in use as the name of the wood-boring [[ambrosia beetle]] genus ''[[Platypus (beetle)|Platypus]]''.<ref name="ABRS">{{cite book|chapter-url=http://www.deh.gov.au/biodiversity/abrs/publications/fauna-of-australia/pubs/volume1b/16-ind.pdf |title=Fauna of Australia |chapter=16 |volume=1b |first=J.R. |last=Grant |publisher=Australian Biological Resources Study (ABRS) |access-date=13 September 2006 |url-status=dead |archive-url=https://web.archive.org/web/20050519143852/http://www.deh.gov.au/biodiversity/abrs/publications/fauna-of-australia/pubs/volume1b/16-ind.pdf |archive-date=19 May 2005 }}</ref> It was independently described as ''Ornithorhynchus paradoxus'' by [[Johann Blumenbach]] in 1800 (from a specimen given to him by [[Sir Joseph Banks]])<ref name="NLA">{{cite web|url=http://www.nla.gov.au/pub/gateways/archive/52/p16a01.html|title=Platypus Paradoxes|publisher=National Library of Australia|date=August 2001|access-date=14 September 2006|archive-date=5 March 2012|archive-url=https://web.archive.org/web/20120305074657/http://www.nla.gov.au/pub/gateways/archive/52/p16a01.html|url-status=live}}</ref> and following the [[principle of priority|rules of priority]] of nomenclature, it was later officially recognised as ''Ornithorhynchus anatinus''.<ref name="ABRS"/>

There is no universally agreed plural form of "platypus" in the English language. Scientists generally use "platypuses" or simply "platypus". Alternatively, the term "platypi" is also used for the plural, although this is a form of [[Dog Latin|pseudo-Latin]];<ref name="APC" /> going by the word's Greek roots the plural would be "platypodes". Early [[United Kingdom|British]] [[settler]]s called it by many names, such as "watermole", "duckbill", and "duckmole".<ref name="APC" /> Occasionally it is specifically called the "duck-billed platypus".

The scientific name ''Ornithorhynchus anatinus'' literally means 'duck-like bird-snout',<ref name="Shaw-1799"/> deriving its [[generic epithet|genus name]] from the Greek root {{transliteration|grc|ornith-}} ({{wikt-lang|grc|ὄρνις|όρνιθ}} ''ornith'' or {{lang|el|ὄρνις}} ''órnīs'' 'bird')<ref>{{cite web |url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=o)/rnis |title=ὄρνις |last1=Liddell |first1=Henry George |last2=Scott |first2=Robert |work=A Greek-English Lexicon |publisher=Perseus Digital Library |date=1940 |access-date=29 September 2022 |archive-date=4 April 2023 |archive-url=https://web.archive.org/web/20230404195515/https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=o)/rnis |url-status=live }}</ref> and the word {{transliteration|grc|rhúnkhos}} ({{wikt-lang|grc|ῥύγχος}} 'snout', 'beak').<ref>{{cite web |url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=r(u/gxos |title=ῥύγχος |last1=Liddell |first1=Henry George |last2=Scott |first2=Robert |work=A Greek-English Lexicon |publisher=Perseus Digital Library |date=1940 |access-date=29 September 2022 |archive-date=23 April 2023 |archive-url=https://web.archive.org/web/20230423120445/https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=r(u/gxos |url-status=live }}</ref> Its [[specific epithet|species name]] is derived from Latin {{wikt-lang|la|anatinus}} ('duck-like') from {{wikt-lang|la|anas}} 'duck'.<ref name="Shaw-1799"/><ref>{{cite encyclopedia |url= https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Danas1 |title= ănăs |last1= Lewis |first1= Charlton T. |last2= Short |first2= Charles |dictionary= A Latin Dictionary |edition=  |publisher= Perseus Digital Library |date= 1879 |access-date= 29 September 2022 |archive-date= 27 September 2023 |archive-url= https://web.archive.org/web/20230927152321/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Danas1 |url-status= live }}</ref> The platypus is the sole living representative or monotypic taxon of its [[Family (biology)|family]] (Ornithorhynchidae).<ref>{{cite web |last=Bess |first=Anna |url=https://animaldiversity.org/accounts/Ornithorhynchidae/ |title=ADW: Ornithorhynchidae: INFORMATION |publisher=Animaldiversity.org |date= |access-date=11 February 2022 |archive-date=17 January 2022 |archive-url=https://web.archive.org/web/20220117035152/https://animaldiversity.org/accounts/Ornithorhynchidae/ |url-status=live }}</ref>
<gallery mode="packed" heights="180px">
platypus-plate.jpg|A book for children published in Germany in 1798
Platypus (Ornithorhynchus anatinus). First Description 1799.jpg|Illustration from the first scientific description in 1799
platypus-sketch.jpg|Colour print from 1863
</gallery>

== Description ==
In [[David Collins (lieutenant governor)|David Collins]]'s account of the new colony 1788–1801, he describes "an amphibious animal, of the mole species", with a drawing.<ref>{{cite book|url=https://archive.org/details/anaccountoftheen12668gut|title=An Account of the English Colony in New South Wales, Volume 2|first=David|last=Collins|access-date=5 July 2017|via=Internet Archive}}</ref>

The body and the broad, flat tail of the platypus are covered with dense, brown, biofluorescent [[fur]] that traps a layer of insulating air to keep the animal warm.<ref name="APC" /><ref name="ABRS" /><ref>{{cite journal |last1=Anich |first1=Paula Spaeth |title=Biofluorescence in the platypus (Ornithorhynchus anatinus) |journal=[[Mammalia (journal)|Mammalia]] |date=15 October 2020 |volume=85 |issue=2 |pages=179–181 |doi=10.1515/mammalia-2020-0027 |doi-access=free }}</ref> The fur is waterproof, and textured like that of a [[Mole (animal)|mole]].<ref>{{cite web |url=http://animal.discovery.com/mammals/platypus/ |title=Platypus: Facts, Pictures: Animal Planet |publisher=Animal.discovery.com |date=16 November 2011 |access-date=8 September 2012 |archive-date=27 July 2011 |archive-url=https://web.archive.org/web/20110727171511/http://animal.discovery.com/mammals/platypus/ |url-status=live }}</ref> The platypus's tail stores fat reserves, an adaptation also found in the [[Tasmanian devil]].<ref name="Guiler">{{cite book|author=Guiler, E.R.|year=1983|chapter=Tasmanian Devil|editor=R. Strahan|title=The Australian Museum Complete Book of Australian Mammals|pages=27–28|publisher=Angus & Robertson|isbn=978-0-207-14454-7}}</ref> [[webbed foot|Webbing]] is more significant on the front feet, which in land walking are folded up in [[knuckle-walking]] to protect the webbing.<ref name="Fish">{{cite journal |last1=Fish |first1=F. E. |last2=Frappell |first2=P. B. |last3=Baudinette |first3=R. V. |last4=Macfarlane |first4=P. M. |title=Energetics of Terrestrial Locomotion of the Platypus Ornithorhynchus Anatinus |journal=Journal of Experimental Biology |date=15 February 2001 |volume=204 |issue=4 |pages=797–803 |doi=10.1242/jeb.204.4.797 |pmid=11171362 |bibcode=2001JExpB.204..797F |hdl-access=free |hdl=2440/12192 }}</ref> The elongated snout and lower jaw are covered in soft skin, forming the bill. The nostrils are located on the snout's dorsal surface, while the eyes and ears are just behind the snout in a groove which closes underwater.<ref name="ABRS" /> Platypuses can give a low growl when disturbed, and a range of vocalisations have been reported in captivity.<ref name="APC" />

Size varies considerably in different regions, with average weight from {{convert|0.7|to|2.4|kg|lboz|abbr=on}}; males have average length {{convert|50|cm|in|0|abbr=on}}, while females are the smaller at {{convert|43|cm|in|frac=2|abbr=on}}.<ref name="ABRS" /> This variation does not seem to follow any particular climatic rule and may be due to other factors such as predation and human encroachment.<ref name="Workshop">{{cite web|url=http://www.medicine.utas.edu.au/research/mono/Taspaper.html|title=Current research on the platypus, ''Ornithorhynchus anatinus'' in Tasmania: Abstracts from the 1999 'Tasmanian Platypus Workshop'|author1=Munks, Sarah |author2=Nicol, Stewart |name-list-style=amp |publisher=University of Tasmania|date=May 1999| access-date = 23 October 2006|archive-url = https://web.archive.org/web/20060830075935/http://www.medicine.utas.edu.au/research/mono/Taspaper.html |archive-date = 30 August 2006|url-status=dead}}</ref>

The platypus has an average [[Core temperature|body temperature]] of about {{convert|32|C|F}}, lower than the {{convert|37|C|F}} typical of [[placentalia|placental mammals]].<ref name="DC">{{cite web|url=http://www.bio.davidson.edu/courses/anphys/1999/White/thermal.htm |title=Thermal Biology of the Platypus |publisher=Davidson College |year=1999 |access-date=14 September 2006 |url-status=dead |archive-url=https://web.archive.org/web/20120306024923/http://www.bio.davidson.edu/courses/anphys/1999/White/thermal.htm |archive-date=6 March 2012 }}</ref> Research suggests this has been a gradual adaptation to harsh environmental conditions among the few marginal surviving monotreme species, rather than a general characteristic of past monotremes.<ref name="temp">{{cite journal |last1=Watson |first1=Jm |last2=Graves |first2=Jam |title=Monotreme Cell-Cycles and the Evolution of Homeothermy |journal=Australian Journal of Zoology |date=1988 |volume=36 |issue=5 |pages=573 |doi=10.1071/ZO9880573 }}</ref><ref name="temp2">{{cite journal |last1=Dawson |first1=Tj |last2=Grant |first2=Tr |last3=Fanning |first3=D |title=Standard Metabolism of Monotremes and the Evolution of Homeothermy. |journal=Australian Journal of Zoology |date=1979 |volume=27 |issue=4 |pages=511 |doi=10.1071/ZO9790511 }}</ref>

In addition to laying eggs, the anatomy, [[ontogeny]], and genetics of monotremes shows traces of similarity to reptiles and birds. The platypus has a [[Reptile|reptilian]] gait with legs on the sides of the body, rather than underneath.<ref name="ABRS" /> The platypus's genes are a possible evolutionary link between the mammalian [[XY sex-determination system|XY]] and bird/reptile [[ZW sex-determination system|ZW]] sex-determination systems, as one of the platypus's five X chromosomes contains the [[DMRT1]] gene, which birds possess on their Z chromosome.<ref name="Graves">{{cite journal |last=Graves |first=Jennifer |date=10 March 2006 |title=Sex Chromosome Specialization and Degeneration in Mammals |journal=Cell |volume=124 |issue=5 |pages=901–914 |doi=10.1016/j.cell.2006.02.024 |pmid=16530039 |s2cid=8379688 |doi-access=free}}</ref>

As in all true mammals, the tiny bones that conduct sound in the [[middle ear]] are fully incorporated into the skull, rather than lying in the jaw as in pre-mammalian [[synapsid]]s. However, the external opening of the ear still lies at the base of the jaw.<ref name="ABRS" /> The platypus has extra bones in the shoulder girdle, including an [[interclavicle]] not found in other mammals.<ref name="ABRS" /> As in many other aquatic and semiaquatic [[vertebrates]], the bones show [[osteosclerosis]], increasing their density to provide ballast.<ref>{{Cite journal | doi = 10.1371/journal.pone.0059146|pmid=23565143|pmc=3615000| title = Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)| journal = PLOS ONE| volume = 8| issue = 4| pages = e59146| year = 2013| last1 = Hayashi | first1 = S.| last2 = Houssaye | first2 = A.| last3 = Nakajima | first3 = Y.| last4 = Chiba | first4 = K.| last5 = Ando | first5 = T.| last6 = Sawamura | first6 = H.| last7 = Inuzuka | first7 = N.| last8 = Kaneko | first8 = N.| last9 = Osaki | first9 = T.|bibcode=2013PLoSO...859146H|doi-access=free}}</ref>

The platypus [[jaw]] is constructed differently from that of other mammals, and the jaw-opening muscle is different.<ref name="ABRS" /> Modern platypus young have three teeth in each of the [[maxilla]]e (one premolar and two [[Molar (tooth)|molars]]) and [[Mandible|dentaries]] (three molars), which they lose before or just after leaving the breeding burrow;<ref name="ABRS" /> adults instead develop heavily [[keratinisation|keratinised]] food-grinding pads called [[ceratodontes]].<ref name="ABRS" /><ref name="Piper-2007" /><ref name="Haeckel1895">{{cite book |last=Haeckel |url=https://books.google.com/books?id=AOi2AAAAIAAJ&pg=PA142 |title=Systematische Phylogenie der Wirbelthiere (Vertebrata) |publisher=Georg Reimer |year=1895 |edition=1 |series=Entwurf einer systematischen Stammesgeschichte |volume=3 |location=Berlin |pages=142–143 |language=de |access-date=16 July 2021 |archive-url=https://web.archive.org/web/20210716071006/https://books.google.com/books?id=AOi2AAAAIAAJ&pg=PA142 |archive-date=16 July 2021 |url-status=live}}</ref> The first upper and third lower cheek teeth of platypus nestlings are small, each having one principal cusp, while the other teeth have two main cusps.<ref>{{cite book |last=Ungar |first=Peter S. |title=Mammal Teeth: Origin, Evolution, and Diversity |publisher=The Johns Hopkins University Press |year=2010 |isbn=978-0-801-89668-2 |page=130 |chapter=Monotremata and Marsupialia}}</ref>

<gallery mode="packed" heights="180px">
Duck-billed platypus (Ornithorhynchus anatinus) diving Scottsdale.jpg|Diving
Duck-billed platypus (Ornithorhynchus anatinus) surfacing Scottsdale.jpg|Surfacing
Duck-billed platypus (Ornithorhynchus anatinus) Scottsdale 4.jpg
</gallery>

=== Venom ===
{{Main|Platypus venom}}
[[File:Platypus spur.JPG|right|thumb|The calcaneus spur on the male's hind limb is used to inject venom.]]

While both male and female platypuses are born with back ankle spurs, only the males' deliver venom.<ref>{{cite web |url=http://www.australianfauna.com/platypus.php |title=Australian Fauna |publisher=Australian Fauna |access-date=14 May 2010 |url-status=dead |archive-url=https://web.archive.org/web/20120529040439/http://www.australianfauna.com/platypus.php |archive-date=29 May 2012 }}</ref><ref>{{cite web |url=http://www.usyd.edu.au/news/84.html?newsstoryid=2267 |title=Platypus venom linked to pain relief |publisher=University of Sydney |date=8 May 2008 |access-date=14 May 2010 |archive-date=21 August 2011 |archive-url=https://web.archive.org/web/20110821151157/http://www.usyd.edu.au/news/84.html?newsstoryid=2267 |url-status=live }}</ref><ref>{{cite web |url=http://rainforest-australia.com/platypus_poison.htm |title=Platypus poison |publisher=Rainforest Australia |access-date=14 May 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100529165453/http://rainforest-australia.com/platypus_poison.htm |archive-date=29 May 2010 }}</ref>
It is powerful enough to kill smaller animals such as dogs, and though it is not lethal to humans, it can inflict weeks of agony.<ref name="PS" /><ref>Weimann, Anya (4 July 2007) [https://web.archive.org/web/20121105043922/http://www.cosmosmagazine.com/news/1423/evolution-platypus-venom-revealed Evolution of platypus venom revealed]. ''[[Cosmos (magazine)|Cosmos]]''.</ref> [[Edema]] rapidly develops around the wound and gradually spreads through the affected limb, and it may develop into an excruciating [[hyperalgesia]] (heightened sensitivity to pain) persisting for days or even months.<ref name="JN">{{cite journal |author=de Plater, G.M. |author2=Milburn, P.J. |author3=Martin, R.L. |year=2001 |title=Venom From the Platypus, ''Ornithorhynchus anatinus'', Induces a Calcium-Dependent Current in Cultured Dorsal Root Ganglion Cells |journal=Journal of Neurophysiology |volume=85 |issue=3 |pages=1340–5 |doi=10.1152/jn.2001.85.3.1340 |pmid=11248005 |s2cid=2452708 }}</ref><ref name="venom">{{cite web |title=The venom of the platypus (''Ornithorhynchus anatinus'') |url=http://www.kingsnake.com/toxinology/old/mammals/platypus.html |url-status=dead |archive-url=https://web.archive.org/web/20120201185504/http://www.kingsnake.com/toxinology/old/mammals/platypus.html |archive-date=1 February 2012 |access-date=13 September 2006}}</ref>

The venom is composed largely of [[defensin]]-like [[protein]]s (DLPs) produced by the immune system, three of which are unique to the platypus.<ref name="PS">{{cite journal| last = Gerritsen| first = Vivienne Baillie| title = Platypus poison| journal = Protein Spotlight| issue = 29| date = December 2002| url = http://www.expasy.org/spotlight/back_issues/sptlt029.shtml| access-date = 14 September 2006| archive-date = 20 October 2008| archive-url = https://web.archive.org/web/20081020054110/http://www.expasy.org/spotlight/back_issues/sptlt029.shtml| url-status = live}}</ref> In other animals, defensins [[lysis|kill]] pathogenic bacteria and viruses, but in platypuses they are also collected into a venom against predators. Venom is produced in the [[wikt:crural|crural]] glands of the male, which are kidney-shaped [[alveolar gland]]s connected by a thin-walled duct to a [[calcaneus]] spur on each hind limb. The female platypus, in common with echidnas, has rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands.<ref name="ABRS" /> Venom production rises among males during the breeding season, and it may be used to assert dominance.<ref name="PS" />

Similar spurs are found on many archaic mammal groups, indicating that this was an ancient general characteristic among mammals.<ref>Jørn H. Hurum, Zhe-Xi Luo, and Zofia Kielan-Jaworowska, 
Were mammals originally venomous?, Acta Palaeontologica Polonica 51 (1), 2006: 1–11</ref>

=== Electrolocation ===
[[File:Platypus electrolocation.svg|thumb|upright=2<!--for readability of svg text-->|The platypus has secondarily acquired [[Electroreception and electrogenesis|electroreception]]. Its receptors are arranged in stripes on its bill, giving it high sensitivity to the sides and below; it makes quick turns of its head as it swims to detect prey.<ref name="Electro1"/>]]

[[Monotremes]] are the only mammals (apart from the [[Guiana dolphin]])<ref>{{cite journal |last1=Czech-Damal |first1=Nicole U. |last2=Liebschner |first2=Alexander |last3=Miersch |first3=Lars |last4=Klauer |first4=Gertrud |last5=Hanke |first5=Frederike D. |last6=Marshall |first6=Christopher |last7=Dehnhardt |first7=Guido |last8=Hanke |first8=Wolf |date=22 February 2012 |title=Electroreception in the Guiana dolphin (Sotalia guianensis) |journal=Proceedings of the Royal Society B: Biological Sciences |volume=279 |issue=1729 |pages=663–668 |doi=10.1098/rspb.2011.1127 |pmc=3248726 |pmid=21795271}}</ref> known to have a sense of [[electroreception]], and the platypus's electroreception is the most sensitive of any monotreme.<ref>{{cite journal |last1=Proske |first1=Uwe |last2=Gregory |first2=J. E. |last3=Iggo |first3=A. |year=1998 |title=Sensory receptors in monotremes |journal=Philosophical Transactions of the Royal Society of London |volume=353 |issue=1372 |pages=1187–1198 |doi=10.1098/rstb.1998.0275 |pmc=1692308 |pmid=9720114}}</ref><ref name="Electro1">{{cite journal |last=Pettigrew |first=John D. |year=1999 |title=Electroreception in Monotremes |url=http://jeb.biologists.org/cgi/reprint/202/10/1447.pdf |url-status=live |journal=The Journal of Experimental Biology |volume=202 |issue=Part 10 |pages=1447–54 |doi=10.1242/jeb.202.10.1447 |pmid=10210685 |archive-url=https://web.archive.org/web/20060928054253/http://jeb.biologists.org/cgi/reprint/202/10/1447.pdf |archive-date=28 September 2006 |access-date=19 September 2006 |doi-access=free|bibcode=1999JExpB.202.1447P }}</ref> Feeding by neither sight nor smell,<ref name="draft_genome" /> the platypus closes its eyes, ears, and nose when it dives.<ref>{{cite journal |author=Gregory, J.E. |author2=Iggo, A. |author3=McIntyre, A.K. |author4=Proske, U. |date=June 1988 |title=Receptors in the Bill of the Platypus |journal=Journal of Physiology |volume=400 |issue=1 |pages=349–366 |doi=10.1113/jphysiol.1988.sp017124 |pmc=1191811 |pmid=3418529}}</ref> Digging in the bottom of streams with its bill, its electroreceptors detect tiny electric currents generated by the muscular contractions of its prey, enabling it to distinguish between animate and inanimate objects.<ref name="Electro1" /> Experiments have shown the platypus will even react to an "artificial shrimp" if a small electric current is passed through it.<ref name="Manning">{{cite book |author1=Manning, A. |url=https://archive.org/details/introductiontoan0000mann_m2z8 |title=An Introduction to Animal Behaviour |author2=Dawkins, M.S. |publisher=Cambridge University Press |year=1998 |edition=5th |url-access=registration}}</ref>

The [[electroreceptor]]s are located in rostrocaudal rows in the skin of the bill, while [[mechanoreceptor]]s for touch are uniformly distributed across the bill. The electrosensory area of the [[cerebral cortex]] is in the tactile [[somatosensory]] area, and some cortical cells receive input from both electroreceptors and mechanoreceptors, suggesting the platypus feels electric fields like touches. These receptors in the bill dominate the [[somatotopic map]] of the platypus brain, in the same way human hands dominate the [[Cortical homunculus|Penfield homunculus map]].<ref name="sensory_platypus">{{cite journal |last1=Pettigrew |first1=John D. |first2=P. R. |last2=Manger |first3=S. L. |last3=Fine |title=The sensory world of the platypus |journal=Philosophical Transactions of the Royal Society of London |pages=1199–1210 |issue=1372 |year=1998 |pmid=9720115|pmc=1692312 |doi=10.1098/rstb.1998.0276 |volume=353 }}</ref><ref name="Ancestors_Tale">{{cite book |first=Richard |last=Dawkins |author-link=Richard Dawkins |title=The Ancestor's Tale, A Pilgrimage to the Dawn of Life |chapter=The Duckbill's Tale |publisher=Houghton Mifflin |location=Boston, Massachusetts |year=2004 |isbn=978-0-618-00583-3 |title-link=The Ancestor's Tale }}</ref>

The platypus can feel the direction of an electric source, perhaps by comparing differences in [[signal strength]] across the sheet of electroreceptors, enhanced by the characteristic side-to-side motion of the animal's head while hunting. It may also be able to determine the distance of moving prey from the time lag between their electrical and mechanical pressure pulses.<ref name="Electro1" />

Monotreme electrolocation for hunting in murky waters may be tied to their tooth loss.<ref name="Masakazu Asahara 2016">Masakazu Asahara; Masahiro Koizumi; Thomas E. Macrini; Suzanne J. Hand; Michael Archer (2016). "Comparative cranial morphology in living and extinct platypuses: Feeding behavior, electroreception, and loss of teeth". Science Advances. 2 (10): e1601329. {{doi|10.1126/sciadv.1601329}}.</ref> The extinct ''[[Obdurodon]]'' was electroreceptive, but unlike the modern platypus it foraged [[pelagic zone|pelagically]].<ref name="Masakazu Asahara 2016" />

=== Eyes ===
In recent studies it has been suggested that the eyes of the platypus are more similar to those of [[Pacific hagfish]] or Northern Hemisphere [[lamprey]]s than to those of most tetrapods. The eyes also contain [[Double cone (biology)|double cones]], unlike most mammals.<ref>{{cite journal |last1=Zeiss|first1=Caroline|title=Comparative retinal morphology of the platypus|doi=10.1002/jmor.10959 |year=2011 |first2=Ivan R. |last3=Murphy|first3=Christopher J. |last4=Dubielzig|first4=Richard W. |journal=Journal of Morphology |volume=272 |issue=8 |pages=949–57 |pmid=21567446|last2=Schwab|s2cid=28546474}}</ref>

Although the platypus's eyes are small and not used under water, several features indicate that vision was important for its ancestors. The [[cornea]]l surface and the adjacent surface of the lens is flat, while the posterior surface of the lens is steeply curved, similar to the eyes of other aquatic mammals such as otters and sea-lions. A [[Temporal bone|temporal]] (ear side) concentration of [[retinal ganglion cell]]s, important for binocular vision, indicates a vestigial role in [[predation]], though the actual visual acuity is insufficient for such activities. Limited acuity is matched by low [[cortical magnification]], a small [[lateral geniculate nucleus]], and a large [[optic tectum]], suggesting that the [[Midbrain tectum|visual midbrain]] plays a more important role than the [[visual cortex]], as in some rodents. These features suggest that the platypus has adapted to an aquatic and nocturnal lifestyle, developing its electrosensory system at the cost of its visual system. This contrasts with the small number of electroreceptors in the [[short-beaked echidna]], which dwells in dry environments, while the [[long-beaked echidna]], which lives in moist environments, is intermediate between the other two monotremes.<ref name="sensory_platypus" />

=== Biofluorescence ===
In 2020, research revealed that platypus fur gives a bluish-green [[biofluorescent]] glow in [[Blacklight|black light]].<ref>{{cite web|last=November 2020|first=Mindy Weisberger-Senior Writer 02|title=Platypuses glow an eerie blue-green under UV light|url=https://www.livescience.com/platypuses-glow-uv-light.html|access-date=7 November 2020|website=livescience.com|date=2 November 2020 |language=en|archive-date=5 November 2020|archive-url=https://web.archive.org/web/20201105063117/https://www.livescience.com/platypuses-glow-uv-light.html|url-status=live}}</ref>

==Distribution, ecology, and behaviour==
[[File:Animaldentition ornithoryncusanatinus.png|thumb|Dentition, as illustrated in Knight's ''Sketches in Natural History'']]
[[File:Ornithorhynchus anatinus -Sydney Aquarium, Sydney, Australia -swimming-6a.ogv|thumbtime=50|right|thumb|Swimming underwater at [[Sydney Aquarium]], Australia]]

The platypus is semiaquatic, inhabiting small streams and rivers over an extensive range from the cold highlands of [[Tasmania]] and the [[Australian Alps]] to the [[tropical rainforest]]s of coastal [[Queensland]] as far north as the base of the [[Cape York Peninsula]].<ref name="DPIW">{{cite web|url=http://www.dpiw.tas.gov.au/inter.nsf/WebPages/BHAN-53573T?open |title=Platypus |publisher=Department of Primary Industries and Water, Tasmania |date=31 August 2006 |access-date=12 October 2006 |url-status=dead |archive-url=https://web.archive.org/web/20061009211345/http://www.dpiw.tas.gov.au/inter.nsf/WebPages/BHAN-53573T?open |archive-date= 9 October 2006 }}</ref>

Inland, its distribution is not well known. It was considered extinct on the [[South Australia]]n mainland, with the last sighting recorded at [[Renmark, South Australia|Renmark]] in 1975.<ref name="Sutton">{{cite web | last=Sutton | first=Malcolm | title=Platypus 'sighting' in the Adelaide Hills sparks camera set-up to capture extinct species - ABC News | website=ABC (Australian Broadcasting Corporation) | date=3 May 2017 | url=https://www.abc.net.au/news/2017-05-04/cameras-set-up-to-confirm-platypus-sighting-in-adelaide-hills/8492400 | access-date=12 October 2020 | archive-date=26 November 2020 | archive-url=https://web.archive.org/web/20201126044708/https://www.abc.net.au/news/2017-05-04/cameras-set-up-to-confirm-platypus-sighting-in-adelaide-hills/8492400 | url-status=live }}</ref> In the 1980s, [[John Wamsley]] created a platypus breeding program in [[Warrawong Sanctuary]] (see [[#Platypus in wildlife sanctuaries|below]]), which subsequently closed.<ref>{{cite web | title=Life reinstated to much-loved Warrawong Wildlife Sanctuary | first=Melissa | last=Keogh | website=The Lead SA | date=3 October 2018 | url=http://theleadsouthaustralia.com.au/industries/regional-showcase/life-reinstated-to-much-loved-warrawong-wildlife-sanctuary/ | access-date=12 October 2020 | archive-date=12 October 2020 | archive-url=https://web.archive.org/web/20201012171044/http://theleadsouthaustralia.com.au/industries/regional-showcase/life-reinstated-to-much-loved-warrawong-wildlife-sanctuary/ | url-status=live }}</ref><ref>{{cite news|last=Adams|first=Prue|title=Wamsley walks away from Earth Sanctuaries|work=Landline|publisher=Australian Broadcasting Corporation|url=https://www.abc.net.au/local/archives/landline/content/2005/s1330004.htm|date=27 March 2005|access-date=12 October 2020|archive-date=12 October 2020|archive-url=https://web.archive.org/web/20201012103440/https://www.abc.net.au/local/archives/landline/content/2005/s1330004.htm|url-status=live}}</ref> In 2017 there were some unconfirmed sightings downstream from the sanctuary,<ref name="Sutton"/> and in October 2020 a nesting platypus was filmed inside the recently reopened sanctuary.<ref name="Sutton 2020">{{cite web | last=Sutton | first=Malcolm | title=V6 Commodore water pump gets the tick from nesting platypus at Warrawong | website=ABC News | publisher=Australian Broadcasting Corporation | date=1 October 2020 | url=https://www.abc.net.au/news/2020-10-02/playtpus-nesting-in-restored-swamp-at-warrawong/12719346 | access-date=7 October 2020 | archive-date=7 October 2020 | archive-url=https://web.archive.org/web/20201007035918/https://www.abc.net.au/news/2020-10-02/playtpus-nesting-in-restored-swamp-at-warrawong/12719346 | url-status=live }}</ref>

There is a population on [[Kangaroo Island]]<ref name="RKI">{{cite web|url=http://www.ees.adelaide.edu.au/research/fbp/ki_res/|archive-url=https://web.archive.org/web/20040706181309/http://www.ees.adelaide.edu.au/research/fbp/ki_res/|url-status=dead|archive-date=6 July 2004|title=Research on Kangaroo Island|publisher=University of Adelaide|date=4 July 2006| access-date = 23 October 2006}}</ref> introduced in the 1920s, said to stand at 150 individuals in the Rocky River region of [[Flinders Chase National Park]]. In the [[2019–20 Australian bushfire season]], large portions of the island burnt, decimating wildlife. However, [[Department for Environment and Water (South Australia)|SA Department for Environment and Water]] recovery teams worked to reinstate their habitat, with a number of sightings reported by April 2020.<ref>{{cite web | title=Find out how platypuses are faring on Kangaroo Island following the bushfires | website=Department for Environment and Water | date=7 April 2020 | url=https://www.environment.sa.gov.au/goodliving/posts/2020/04/platypus-recovery-on-ki | access-date=12 October 2020 | archive-date=21 July 2021 | archive-url=https://web.archive.org/web/20210721003955/https://www.environment.sa.gov.au/goodliving/posts/2020/04/platypus-recovery-on-ki | url-status=live }}</ref>

The platypus is no longer found in the main [[Murray–Darling basin|Murray–Darling Basin]], possibly due to declining [[water quality]] from land clearing and [[irrigation]]<ref name="CSIRO">{{cite web|url=http://www.clw.csiro.au/publications/technical97/tr23-97.pdf|title=Impacts of water management in the Murray-Darling Basin on the platypus (''Ornithorhynchus anatinus'') and the water rat (''Hydromus chrysogaster'')|author1=Scott, Anthony|author2=Grant, Tom|publisher=CSIRO Australia|date=November 1997|access-date=23 October 2006|archive-date=15 March 2016|archive-url=https://web.archive.org/web/20160315115754/http://www.clw.csiro.au/publications/technical97/tr23-97.pdf|url-status=live}}</ref> although it is found in the [[Goulburn River]] in Victoria.<ref>{{cite web|url=https://platypus.asn.au/platypus-burrows/ |title=Platypus burrows |website=Australian Platypus Conservancy|date=6 March 2024 }}</ref> Along the coastal river systems, its distribution is unpredictable: absent in some relatively healthy rivers, but present in some quite degraded ones, for example the lower [[Maribyrnong River|Maribyrnong]].<ref name="APC2">{{cite web|url=http://www.platypus.asn.au/platypus_in_country_areas.html |archive-url=https://web.archive.org/web/20160917002720/http://www.platypus.asn.au/platypus_in_country_areas.html |archive-date=17 September 2016 |title=Platypus in Country Areas |publisher=Australian Platypus Conservancy |access-date=23 October 2006 |url-status=dead }}</ref>

In captivity, platypuses have survived to 30 years of age, and wild specimens have been recaptured when 24 years old. [[Mortality rate]]s for adults in the wild appear to be low.<ref>{{cite news|title=Oldest-known wild platypus gives new insights into longevity of enigmatic Australian species|website=ABC Science |author=Peter de Kruijff|url=https://www.abc.net.au/news/science/2024-02-15/new-platypus-age-records-for-captive-and-wild-specimens/103450732|date=14 February 2024}}</ref> Natural predators include [[snake]]s, [[Rakali|water rats]], [[goanna]]s, [[hawk]]s, [[owl]]s, and [[eagle]]s. Low platypus numbers in northern Australia are possibly due to predation by [[crocodile]]s.<ref name="EPA">{{cite web|url=http://www.epa.qld.gov.au/nature_conservation/wildlife/az_of_animals/platypus.html |title=Platypus |publisher=Environmental Protection Agency/Queensland Parks and Wildlife Service |year=2006 |access-date=24 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20091021042522/http://www.epa.qld.gov.au/nature_conservation/wildlife/az_of_animals/platypus.html |archive-date=21 October 2009 }}</ref> The introduction of [[red fox]]es in 1845 for sport hunting may have had some impact on its numbers on the mainland.<ref name="Workshop" /> The platypus is generally [[nocturnal]] and [[crepuscular]], but can be active on overcast days.<ref name="EC">{{cite web|url=http://www.biology.iastate.edu/InternationalTrips/1Australia/04papers/CromerMonotrRepro.htm |title=Monotreme Reproductive Biology and Behavior |publisher=Iowa State University |author=Cromer, Erica |date=14 April 2004 |access-date=18 June 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090313030236/http://www.biology.iastate.edu/InternationalTrips/1Australia/04papers/CromerMonotrRepro.htm |archive-date=13 March 2009 }}</ref><ref name="HCP">{{cite journal|journal=Philosophical Transactions: Biological Sciences|title=Field biology of the platypus (''Ornithorhynchus anatinus''): historical and current perspectives|volume=353|issue=1372|author=Grant, T.G.|author2= Temple-Smith, P.D. |year=1998|pmid=9720106|pages=1081–91|pmc=1692311 | doi = 10.1098/rstb.1998.0267}}</ref> Its habitat bridges [[river]]s and the [[riparian zone]], where it finds both prey and river banks to dig resting and nesting burrows.<ref name="HCP" /> It may have a range of up to {{convert|7|km|mi|abbr=on}}, with a male's home range overlapping those of three or four females.<ref name="AJZ4">{{cite journal|journal=Australian Journal of Zoology|title=Spatial-Organization and Movement Patterns of Adult Male Platypus, ''Ornithorhynchus anatinus'' (Monotremata, Ornithorhynchidae) |volume=43 |issue=1 |author= Gardner, J. L. |author2=Serena, M. |year=1995 |pages=91–103 | doi = 10.1071/ZO9950091
}}</ref>

The platypus is an excellent swimmer and spends much of its time in the water foraging for food. It has a swimming style unique among mammals,<ref name="dpipwe">{{cite web|url=https://dpipwe.tas.gov.au/wildlife-management/fauna-of-tasmania/mammals/echidnas-and-platypus/platypus/platypus-in-tasmania|title=Platypus in Tasmania {{!}} Department of Primary Industries, Parks, Water and Environment, Tasmania|website=dpipwe.tas.gov.au|access-date=10 April 2020|archive-date=8 March 2020|archive-url=https://web.archive.org/web/20200308221910/https://dpipwe.tas.gov.au/wildlife-management/fauna-of-tasmania/mammals/echidnas-and-platypus/platypus/platypus-in-tasmania|url-status=live}}</ref> propelling itself by alternate strokes of the front feet, while the webbed hind feet are held against the body and only used for steering, along with the tail.<ref name="Rowing">{{cite journal|journal=The Journal of Experimental Biology|volume=200|issue=20|pages=2647–52|title=Energetics of Swimming by the Platypus ''Ornithorhynchus anatinus'': Metabolic Effort Associated with Rowing|author=Fish, F.E.|author2=Baudinette, R.V.|author3=Frappell, P.B.|author4=Sarre, M.P.|year=1997|doi=10.1242/jeb.200.20.2647|url=http://jeb.biologists.org/cgi/reprint/200/20/2647.pdf|pmid=9359371|bibcode=1997JExpB.200.2647F |access-date=23 October 2006|archive-date=26 September 2009|archive-url=https://web.archive.org/web/20090926191559/http://jeb.biologists.org/cgi/reprint/200/20/2647.pdf|url-status=live}}</ref> It can maintain its relatively low body temperature of about 32{{spaces}}°C (90{{spaces}}°F) while foraging for hours in water below 5{{spaces}}°C (41{{spaces}}°F).<ref name="ABRS" /> Dives normally last around 30 seconds, with an estimated aerobic limit of 40 seconds, with 10 to 20 seconds at the surface between dives.<ref name="Bethge">{{cite thesis|url=http://eprints.utas.edu.au/2326/|title=Energetics and foraging behaviour of the platypus|publisher=University of Tasmania|author=Philip Bethge|date=April 2002|doi=10.25959/23210588.v1 |access-date=21 June 2009|archive-date=25 October 2018|archive-url=https://web.archive.org/web/20181025070921/https://eprints.utas.edu.au/2326/|type=thesis |url-status=live}}</ref><ref>{{cite journal|journal=The Journal of Applied Ecology|jstor=2404239|title=The Diving Behaviour of the Platypus (''Ornithorhynchus anatinus'') in Waters with Different Trophic Status|author=Kruuk, H. |volume=30|issue=4|year=1993|pages=592–8 | doi = 10.2307/2404239|bibcode=1993JApEc..30..592K }}</ref>

The platypus rests in a short, straight burrow in the riverbank about {{convert|30|cm|in|0|abbr=on}} above water level, its oval entrance-hole often [[Camouflage|hidden]] under a tangle of roots.<ref name="dpipwe" /> It may sleep up to 14 hours per day, after half a day of diving.<ref>{{cite journal |author=Holland, Jennifer S. |title=40 Winks? |journal= National Geographic|volume=220 |issue=1 |date=July 2011 }}</ref>

=== Diet ===
The platypus is a [[carnivore]], feeding on [[annelid]] worms, [[Larva|insect larvae]], freshwater [[shrimp]], and [[Cherax|yabby]] ([[crayfish]]) that it digs out of the riverbed with its snout or catches while swimming. It carries prey to the surface in cheek-pouches before eating it.<ref name="dpipwe" /> It eats about 20% of its own weight each day, which requires it to spend an average of 12 hours daily looking for food.<ref name="Bethge" />

=== Reproduction ===
[[File:Ornithorhynchus anatinus - nest with eggs - MUSE.JPG|thumb|Platypus's nest with eggs (replica)]]

The species has a single [[breeding season]] between June and October, with some local variation.<ref name="EPA" /> Investigations have found both resident and transient platypuses, and suggest a [[Polygyny in animals|polygynous]] mating system.<ref name="AJZ2">{{cite journal|journal=Australian Journal of Zoology|title=Aspects of Lactation in the Platypus, ''Ornithorhynchus anatinus'' (Monotremata), in Waters of Eastern New South Wales|author=Grant, T. R. |author2=Griffiths, M. |author3=Leckie, R.M.C. |volume=31|issue=6|pages=881–9|doi=10.1071/ZO9830881|year=1983}}</ref> Females are believed to become sexually mature in their second year, with breeding observed in animals over nine years old.<ref name="AJZ2"/> During [[Copulation (zoology)|copulation]], the male grasps the female's tail with his bill, wraps his tail around her, then grips her neck or shoulder, everts his [[penis]] through his [[cloaca]], and inserts it into her [[urogenital sinus]].<ref>{{Cite book |last=Grant |first=Tom |url=https://books.google.com/books?id=bu8rIm-TdqwC&dq=platypus+copulation&pg=PA17 |title=Platypus |date=2007-10-02 |publisher=Csiro Publishing |isbn=978-0-643-10127-2 |language=en}}</ref> He takes no part in nesting, living in his year-long resting burrow. After mating, the female constructs a deep, elaborate nesting burrow up to {{convert|20|m|ft|round=5|abbr=on}} long.<ref name="ADW">{{cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Ornithorhynchidae.html |title=Family Ornithorhynchidae (platypus) |author1=Anna Bess Sorin |author2=Phil Myers |name-list-style=amp |publisher=University of Michigan Museum of Zoology |year=2001 |access-date=24 October 2006 |archive-date=10 April 2011 |archive-url=https://web.archive.org/web/20110410142645/http://animaldiversity.ummz.umich.edu/site/accounts/information/Ornithorhynchidae.html |url-status=live }}</ref> She tucks fallen leaves and reeds underneath her curled tail, dragging them to the burrow to soften the tunnel floor with folded wet leaves, and to line the nest at the end with bedding.<ref name="APC" />

The male platypus has [[penile spines]] and an asymmetrical [[glans penis]], with the right side smaller than the left.<ref>{{Cite book |last1=Vogelnest |first1=Larry |url=https://books.google.com/books?id=4d6VDwAAQBAJ&dq=platypus&pg=PA64 |title=Current Therapy in Medicine of Australian Mammals |last2=Portas |first2=Timothy |date=2019-05-01 |publisher=Csiro Publishing |isbn=978-1-4863-0752-4 |language=en}}</ref> The female has two [[Ovary|ovaries]], but only the left one is functional.<ref>{{Cite book |last1=Vogelnest |first1=Larry |url=https://books.google.com/books?id=p8cDEAAAQBAJ&pg=PA107 |title=Medicine of Australian Mammals |last2=Woods |first2=Rupert |date=18 August 2008 |publisher=Csiro Publishing |isbn=978-0-643-09797-1 |language=en |access-date=27 April 2024 |archive-date=25 May 2024 |archive-url=https://web.archive.org/web/20240525044226/https://books.google.com/books?id=p8cDEAAAQBAJ&pg=PA107#v=onepage&q&f=false |url-status=live }}</ref><ref name="EC" /> She lays one to three (usually two) small, leathery eggs (similar to those of reptiles), about {{convert|11|mm|in|frac=32|abbr=on}} in diameter and slightly rounder than bird eggs.<ref name="BSED">{{cite journal|journal= Philosophical Transactions of the Royal Society B: Biological Sciences|title=Early development and embryology of the platypus|author=Hughes, R. L. |author2=Hall, L. S. |volume=353|issue=1372|pages=1101–14|date=28 July 1998|pmid= 9720108|pmc= 1692305 | doi = 10.1098/rstb.1998.0269}}</ref> The eggs develop ''[[Uterus|in utero]]'' for about 28 days, with only about 10 days of external [[Avian incubation|incubation]] (in contrast to a chicken egg, which spends about one day in tract and 21 days externally).<ref name="EC" /> The female curls around the incubating eggs, which develop in three phases.<ref name="RS2" /> In the first, the [[embryo]] has no functional organs and relies on the [[yolk sac]] for sustenance, until the sac is absorbed.<ref>{{cite web|title=Ockhams Razor|work=The Puzzling Platypus|url=http://www.abc.net.au/radionational/programs/ockhamsrazor/the-puzzling-platypus/3492688|access-date=2 December 2006|date=20 July 2001|archive-date=9 August 2017|archive-url=https://web.archive.org/web/20170809103030/http://www.abc.net.au/radionational/programs/ockhamsrazor/the-puzzling-platypus/3492688|url-status=live}}</ref> During the second phase, the digits develop, and in the last phase, the [[egg tooth]] appears.<ref name="RS2">{{cite journal|journal=Philosophical Transactions: Biological Sciences|title =The development of the external features of the platypus (''Ornithorhynchus anatinus'')|author=Manger, Paul R. |author2=Hall, Leslie S. |author3=Pettigrew, John D. |volume=353|issue=1372|pages=1115–25|date=29 July 1998|pmid=9720109|pmc=1692310|doi =10.1098/rstb.1998.0270}}</ref> At first, European [[natural history|naturalists]] could hardly believe that the female platypus lays eggs, but this was finally confirmed by [[William Hay Caldwell]] in 1884.<!--for wiring London and other such trivia see that article--><ref name="ABRS"/><ref name="PS"/>

Most mammal zygotes go through [[holoblastic]] cleavage, splitting into multiple divisible daughter cells. However, [[monotremes]] like the platypus, along with [[Sauropsida|reptiles and birds]], undergo meroblastic cleavage, in which the ovum does not split completely. The cells at the edge of the yolk remain continuous with the egg's cytoplasm, allowing the yolk and embryo to exchange waste and nutrients with the egg through the cytoplasm.<ref>{{cite journal|author=Myers, P. Z.|url=http://www.nature.com/scitable/topicpage/interpreting-shared-characteristics-the-platypus-genome-44568|title=Interpreting Shared Characteristics: The Platypus Genome|journal=Nature Education|volume=1|issue=1|page=462008|year=2008|access-date=26 March 2015|archive-date=4 March 2018|archive-url=https://web.archive.org/web/20180304124410/http://www.nature.com/scitable/topicpage/interpreting-shared-characteristics-the-platypus-genome-44568|url-status=live}}</ref>

Young platypus are called "puggles". Newly hatched platypuses are vulnerable, blind, and hairless, and are fed by the mother's milk, that provides all the requirements for growth and development.<ref>{{cite web|last1=Stannard|first1=Hayley J.|last2=Old|first2=Julie M.|title=Wallaby joeys and platypus puggles are tiny and undeveloped when born. But their mother's milk is near-magical|url=https://theconversation.com/wallaby-joeys-and-platypus-puggles-are-tiny-and-undeveloped-when-born-but-their-mothers-milk-is-near-magical-207726|publisher=The Conversation|year=2023|access-date=25 October 2023|archive-date=10 November 2023|archive-url=https://web.archive.org/web/20231110202925/https://theconversation.com/wallaby-joeys-and-platypus-puggles-are-tiny-and-undeveloped-when-born-but-their-mothers-milk-is-near-magical-207726|url-status=live}}</ref><ref>{{cite journal|last1=Stannard|first1=Hayley J.|last2=Miller|first2=Robert D.|last3=Old|first3=Julie M.|title=Marsupial and monotreme milk – a review of its nutrients and immune properties|journal=PeerJ|year=2020|volume=8|page=e9335|doi=10.7717/peerj.9335 |pmid=32612884 |pmc=7319036 |doi-access=free }}</ref> The platypus's [[mammary gland]]s lack [[teat]]s, with milk released through pores in the skin. The milk pools in grooves on the mother's abdomen, allowing the young to lap it up.<ref name="APC" /><ref name="EPA" /> After they hatch, the offspring are milk-fed for three to four months.

During incubation and weaning, the mother initially leaves the burrow only for short periods to forage. She leaves behind her a number of thin soil plugs along the length of the burrow, possibly to protect the young from predators; pushing past these on her return squeezes water from her fur and allows the burrow to remain dry.<ref name="QM">{{cite web|url=http://www.qm.qld.gov.au/inquiry/factsheets/leaflet0010.pdf|title=Egg-laying mammals|publisher=Queensland Museum|date=November 2000| access-date = 19 June 2009|archive-url = https://web.archive.org/web/20080722180447/http://www.qm.qld.gov.au/inquiry/factsheets/leaflet0010.pdf |archive-date = 22 July 2008|url-status=dead}}</ref> After about five weeks, the mother begins to spend more time away from her young, and at around four months, the young emerge from the burrow.<ref name="EPA" /> A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates it uses to grind food.<ref name="Piper-2007">{{cite book |author-link=Ross Piper |first=Ross |last=Piper |title=Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals |url=https://archive.org/details/extraordinaryani0000pipe |url-access=registration |publisher=[[Greenwood Press (publisher)|Greenwood Press]] |year=2007 |isbn=978-0-313-33922-6 }}</ref>

== Evolution ==
{{cladogram
|caption=Evolutionary relationships between the platypus and other mammals<ref name="LecointreGuyader2006">{{cite book|last1=Lecointre|first1=Guillaume|last2=Le Guyader|first2=Hervé|title=The Tree of Life: A Phylogenetic Classification|url=https://archive.org/details/treeoflifephylog0000leco|url-access=registration|access-date=28 March 2015|year=2006|publisher=Harvard University Press|isbn=978-0-674-02183-9}}</ref>
|cladogram=
{{clade
|1={{clade
   |1={{clade
      |1='''Platypus'''
      |2=[[Echidna]]s
      }}
   |label2=''{{spaces}}live{{spaces}}birth{{spaces}}''
   |2={{clade
      |1=[[Marsupial]]s
      |label2=''{{spaces}}true{{spaces}}placenta{{spaces}}''
      |2=[[Placental]]s
      }}
   }}
}}
}}

The platypus and other monotremes were very poorly understood, and some of the 19th century myths that grew up around them{{snd}}for example, that the monotremes were "inferior" or [[Reptile|quasireptilian]]{{snd}}still endure.<ref name="Rodent">{{cite journal|journal=Philosophical Transactions: Biological Sciences|title=The platypus is not a rodent: DNA hybridization, amniote phylogeny and the palimpsest theory|author=Kirsch, John A. W. |author2=Mayer, Gregory C. |volume=353|issue=1372|pages=1221–37|date=29 July 1998|pmid=9720117|pmc=1692306|doi=10.1098/rstb.1998.0278}}</ref> In 1947, [[William King Gregory]] theorised that placental mammals and marsupials may have diverged earlier, and a subsequent branching divided the monotremes and marsupials, but later research and fossil discoveries have suggested this is incorrect.<ref name="Rodent" /><ref name="JM">{{cite journal |journal=Nature |volume=416 |issue= 6877|pages=165–8 |year=2002 |doi=10.1038/416165a |title=The first Jurassic mammal from South America |author=Rauhut, O.W.M.|author2= Martin, T.|author3= Ortiz-Jaureguizar, E.|author4= Puerta, P. |pmid=11894091|bibcode=2002Natur.416..165R|hdl=11336/99461 |s2cid=4346804 |hdl-access=free }}</ref> In fact, modern monotremes are the survivors of an early branching of the mammal tree, and a later branching is thought to have led to the [[marsupial]] and placental groups.<ref name="Rodent" /><ref name="JME">{{cite journal|journal=Journal of Mammalian Evolution|title=Evolution of the Monotremes: Phylogenetic Relationship to Marsupials and Eutherians, and Estimation of Divergence Dates Based on α-Lactalbumin Amino Acid Sequences|author=Messer, M.|author2= Weiss, A.S.|author3= Shaw, D.C.|author4= Westerman, M.|volume=5|issue=1|pages=95–105|date=March 1998 | doi = 10.1023/A:1020523120739|s2cid=39638466}}</ref> [[Molecular clock]] and fossil dating suggest platypuses split from [[echidna]]s around 19–48{{spaces}}million years ago.<ref name="Phillips">{{cite journal | author = Phillips MJ|author2= Bennett TH|author3= Lee MS | year = 2009 | title = Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas | journal =Proc. Natl. Acad. Sci. U.S.A. | volume = 106 | issue = 40| pages = 17089–94 | doi = 10.1073/pnas.0904649106 | pmid = 19805098 | pmc = 2761324 | bibcode = 2009PNAS..10617089P |doi-access= free}}</ref>
[[File:Steropodon BW.jpg|thumb|right|Reconstruction of ancient platypus relative ''Steropodon'']]

The oldest discovered fossil of the modern platypus dates back to about 100,000 years ago during the [[Quaternary]] period, though a limb bone of ''Ornithorhynchus'' is known from [[Pliocene]]-aged strata.<ref>{{cite book|author=Musser, A.M.|editor1=Merrick, J.R.|editor2=Archer, M.|editor3=Hickey, G.M.|editor4=Lee, M.S.Y.|year=2006|chapter=26. Furry Egg-layers: Monotreme Relationships and Radiations|title=Evolution and Biogeography of Australasian Vertebrates|publisher=Auscipub|pages=523–550|isbn=978-0975779002}}</ref> The extinct monotremes ''[[Teinolophos]]'' and ''[[Steropodon]]'' from the [[Cretaceous]] were once thought to be closely related to the modern platypus,<ref name="JM" /> but are now considered more basal taxa.<ref name="Thomas H. Rich 2016">{{Cite journal |last1=Rich |first1=Thomas H. |last2=Hopson |first2=James A. |last3=Gill |first3=Pamela G. |last4=Trusler |first4=Peter |last5=Rogers-Davidson |first5=Sally |last6=Morton |first6=Steve |last7=Cifelli |first7=Richard L. |last8=Pickering |first8=David |last9=Kool |first9=Lesley |year=2016 |title=The mandible and dentition of the Early Cretaceous monotreme Teinolophos trusleri |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=40 |issue=4 |pages=475–501 |doi=10.1080/03115518.2016.1180034 |bibcode=2016Alch...40..475R |s2cid=89034974 |hdl=1885/112071 |hdl-access=free }}</ref> The fossilised ''Steropodon'' was discovered in [[New South Wales]] and is composed of an opalised lower jawbone with three molar teeth (whereas the adult contemporary platypus is toothless). The molar teeth were initially thought to be [[Tribosphenic molar|tribosphenic]], which would have supported a variation of Gregory's theory, but later research has suggested, while they have three cusps, they evolved under a separate process.<ref name="MS">{{cite journal|journal=Acta Palaeontologica Polonica|url=http://www.app.pan.pl/archive/published/app47/app47-487.pdf|title=New data on the Paleocene monotreme ''Monotrematum sudamericanum'', and the convergent evolution of triangulate molars|author=Pascual, R.|author2=Goin, F.J.|author3=Balarino, L.|author4=Udrizar Sauthier, D.E.|volume=47|issue=3|pages=487–492|year=2002|access-date=18 March 2009|archive-date=9 August 2017|archive-url=https://web.archive.org/web/20170809023141/http://www.app.pan.pl/archive/published/app47/app47-487.pdf|url-status=live}}</ref> The fossil jaw of ''Teinolophos'' is thought to be about 110{{spaces}}million years old, making it the oldest mammal fossil found in Australia. Unlike the modern platypus (and [[echidna]]s), ''Teinolophos'' lacked a beak.<ref name="Thomas H. Rich 2016" />

In 2024, [[Late Cretaceous]] ([[Cenomanian]])-aged fossil specimens of actual early platypus relatives were recovered from the same rocks as ''Steropodon'', including the [[Basal (phylogenetics)|basal]] ''[[Opalios]]'' and the more derived ''[[Dharragarra]]'', the latter of which may be the oldest member of the platypus [[Stem group|stem]]-lineage, as it retains the same [[Dentition|dental formula]] found in Cenozoic platypus relatives.<ref name=":0">{{cite journal |last1=Flannery |first1=Timothy F. |last2=McCurry |first2=Matthew R. |last3=Rich |first3=Thomas H. |last4=Vickers-Rich |first4=Patricia |last5=Smith |first5=Elizabeth T. |last6=Helgen |first6=Kristofer M. |title=A diverse assemblage of monotremes (Monotremata) from the Cenomanian Lightning Ridge fauna of New South Wales, Australia |journal=Alcheringa: An Australasian Journal of Palaeontology |date=2 April 2024 |volume=48 |issue=2 |pages=319–337 |doi=10.1080/03115518.2024.2348753 |doi-access=free |bibcode=2024Alch...48..319F }}</ref> ''[[Monotrematum]]'' and ''[[Patagorhynchus]]'', two other fossil relatives of the platypus, are known from the latest Cretaceous ([[Maastrichtian]]) and the mid-[[Paleocene]] of [[Argentina]], indicating that some monotremes managed to colonize [[South America]] from Australia when the two continents were connected via [[Antarctica]]. These are also considered potential members of the platypus stem-lineage.<ref name="MS" /><ref name="patagonia">{{Cite journal|title = A platypus in Patagonia (Ancient life – 1992)|last = Folger|first = Tim| date = 1993 |journal = Discover|volume = 14|issue = 1|page = 66}}</ref><ref name=":0" />  The closest fossil relative of the platypus was ''[[Obdurodon]]'', known from the late [[Oligocene]] to the [[Miocene]] of Australia. It closely resembled the modern platypus, aside from the presence of molar teeth.<ref name=":0" /> A fossilised tooth of the giant platypus ''[[Obdurodon tharalkooschild]]'' was dated 5–15{{spaces}}million years ago. Judging by the tooth, the animal measured 1.3 metres long, making it the largest platypus on record.<ref>{{cite news|url = http://www.zmescience.com/science/geology/platypus-fossil-paleontology-05112013/|title = 'Platypus-zilla' fossil unearthed in Australia|newspaper = ZME Science|last = Mihai|first = Andrei|year = 2013|access-date = 5 November 2013|archive-date = 21 July 2021|archive-url = https://web.archive.org/web/20210721004004/https://www.zmescience.com/science/geology/platypus-fossil-paleontology-05112013/|url-status = live}}</ref>

The loss of teeth in the modern platypus has long been enigmatic, as a distinctive lower molar tooth row was previously present in its lineage for over 95 million years. Even its closest relative, ''Obdurodon'', which otherwise closely resembles the platypus, retained this tooth row. More recent studies indicate that this tooth loss was a geologically very recent event, occurring only around the [[Pliocene|Plio]]-[[Pleistocene]] (around 2.5 million years ago), when the [[rakali]], a large semiaquatic [[rodent]], colonized Australia from [[New Guinea]]. The platypus, which previously fed on a wide array of hard and soft-bodied prey, was outcompeted by the rakali for hard-bodied prey such as crayfish and mussels. This competition may have selected for the loss of teeth in the platypus and their replacement by horny pads, as a way of specializing for softer-bodied prey, over which the rakali did not compete with it.<ref name=":0" />

=== Genome ===
[[File:Platypus skeleton Pengo.jpg|thumb|Platypus skeleton]]

Because of the early divergence from the [[Theria|therian mammals]] and the low numbers of extant monotreme species, the platypus is a frequent subject of research in evolutionary biology. In 2004, [[research]]ers at the [[Australian National University]] discovered the platypus has ten [[sex chromosome]]s, compared with two (XY) in most other mammals. These ten chromosomes form five unique pairs of XY in males and XX in females, i.e. males are X{{sub|1}}Y{{sub|1}}X{{sub|2}}Y{{sub|2}}X{{sub|3}}Y{{sub|3}}X{{sub|4}}Y{{sub|4}}X{{sub|5}}Y{{sub|5}}.<ref name="discover">{{cite web|url=http://discovermagazine.com/2005/apr/sex-ys-platypuses0425/|title=Sex, Ys, and Platypuses|publisher=Discover|first=Jocelyn|last=Selim|date=25 April 2005|access-date=7 May 2008|archive-date=16 May 2008|archive-url=https://web.archive.org/web/20080516233225/http://discovermagazine.com/2005/apr/sex-ys-platypuses0425|url-status=live}}</ref> One of the X chromosomes of the platypus has great homology to the bird Z chromosome.<ref>{{Cite journal|author1=Frank Grützner|author2=Willem Rens|author3=Enkhjargal Tsend-Ayush|author4=Nisrine El-Mogharbel|author5=Patricia C. M. O'Brien|author6=Russell C. Jones|author7=Malcolm A. Ferguson-Smith|author8=Jennifer A. Marshall Graves|title=In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes|journal=Nature|volume=432|issue=7019|pages=913–917|date=16 December 2004|doi=10.1038/nature03021|pmid=15502814|bibcode=2004Natur.432..913G|s2cid=4379897}}
</ref> The platypus genome also has both reptilian and mammalian genes associated with egg fertilisation.<ref name="draft_genome">{{cite journal| journal = Nature| volume = 453| issue = 7192| pages = 175–183| title = Genome analysis of the platypus reveals unique signatures of evolution| date = 8 May 2008| doi = 10.1038/nature06936| author = Warren, Wesley C.| pmid = 18464734| pmc = 2803040 |display-authors=etal|bibcode=2008Natur.453..175W}}</ref><ref>{{cite journal |title=Beyond the Platypus Genome – 2008 Boden Research Conference |journal=Reprod Fertil Dev |volume=21 |issue=8 |pages=i–ix, 935–1027 |year=2009 |url=http://www.publish.csiro.au/nid/44/issue/4849.htm |access-date=3 March 2012 |archive-date=21 November 2015 |archive-url=https://web.archive.org/web/20151121130525/http://www.publish.csiro.au/nid/44/issue/4849.htm |url-status=live }}</ref> Though the platypus lacks the mammalian sex-determining gene [[SRY]], a study found that the mechanism of sex determination is the [[Anti-Müllerian hormone|AMH gene]] on the oldest [[Y chromosome]].<ref>{{cite journal|last1=Cortez|first1=Diego|last2=Marin|first2=Ray|last3=Toledo-Flores|first3=Deborah|last4=Froidevaux|first4=Laure|last5=Liechti|first5=Angélica|last6=Waters|first6=Paul D.|last7=Grützner|first7=Frank|last8=Kaessmann|first8=Henrik|year=2014|title=Origins and functional evolution of Y chromosomes across mammals|journal=Nature|volume=508|issue=7497|pages=488–493|doi=10.1038/nature13151|pmid=24759410|bibcode=2014Natur.508..488C|s2cid=4462870}}</ref><ref>{{cite news|last1=Salleh|first1=Anna|title=Platypus Sex 'Master Switch' Identified|url=http://www.abc.net.au/science/articles/2014/05/05/3994897.htm|publisher=Australian Broadcasting Corporation|date=5 May 2014|access-date=5 June 2014|archive-date=6 July 2016|archive-url=https://web.archive.org/web/20160706211627/http://www.abc.net.au/science/articles/2014/05/05/3994897.htm|url-status=live}}</ref> A draft version of the platypus genome sequence was published in ''[[Nature (journal)|Nature]]'' on 8{{spaces}}May 2008, revealing both reptilian and mammalian elements, as well as two genes found previously only in birds, amphibians, and fish. More than 80% of the platypus's genes are common to the other mammals whose genomes have been sequenced.<ref name="draft_genome" /> An updated genome, the most complete on record, was published in 2021, together with the genome of the [[short-beaked echidna]].<ref>{{cite journal |last1=Zhou |first1=Yang |last2=Shearwin-Whyatt |first2=Linda |last3=Li |first3=Jing |last4=Song |first4=Zhenzhen |last5=Hayakawa |first5=Takashi |last6=Stevens |first6=David |last7=Fenelon |first7=Jane C. |last8=Peel |first8=Emma |last9=Cheng |first9=Yuanyuan |last10=Pajpach |first10=Filip |last11=Bradley |first11=Natasha |last12=Suzuki |first12=Hikoyu |last13=Nikaido |first13=Masato |last14=Damas |first14=Joana |last15=Daish |first15=Tasman |last16=Perry |first16=Tahlia |last17=Zhu |first17=Zexian |last18=Geng |first18=Yuncong |last19=Rhie |first19=Arang |last20=Sims |first20=Ying |last21=Wood |first21=Jonathan |last22=Haase |first22=Bettina |last23=Mountcastle |first23=Jacquelyn |last24=Fedrigo |first24=Olivier |last25=Li |first25=Qiye |last26=Yang |first26=Huanming |last27=Wang |first27=Jian |last28=Johnston |first28=Stephen D. |last29=Phillippy |first29=Adam M. |last30=Howe |first30=Kerstin |last31=Jarvis |first31=Erich D. |last32=Ryder |first32=Oliver A. |last33=Kaessmann |first33=Henrik |last34=Donnelly |first34=Peter |last35=Korlach |first35=Jonas |last36=Lewin |first36=Harris A. |last37=Graves |first37=Jennifer |last38=Belov |first38=Katherine |last39=Renfree |first39=Marilyn B. |last40=Grutzner |first40=Frank |last41=Zhou |first41=Qi |last42=Zhang |first42=Guojie |title=Platypus and echidna genomes reveal mammalian biology and evolution |journal=Nature |date=29 April 2021 |volume=592 |issue=7856 |pages=756–762 |doi=10.1038/s41586-020-03039-0 |pmid=33408411 |pmc=8081666 |bibcode=2021Natur.592..756Z |doi-access=free }}</ref>

== Conservation ==
=== Status and threats ===
Except for its loss from the state of South Australia, the platypus occupies the same general distribution as it did prior to [[European settlement of Australia]]. However, local changes and fragmentation of distribution due to human modification of its habitat are documented. Its historical abundance is unknown and its current abundance difficult to gauge, but it is assumed to have declined in numbers, although as of 1998 was still being considered as common over most of its current range.<ref name="HCP" /> The species was extensively hunted for its fur until the early years of the 20th century. Although the species gained legal protections beginning in Victoria in 1890<ref name=1890act>{{cite web | title=Game Act 1890 | website=[[Australasian Legal Information Institute]] | url=http://classic.austlii.edu.au/au/legis/vic/hist_act/ga189043/ | access-date=9 August 2023 | archive-date=9 August 2023 | archive-url=https://web.archive.org/web/20230809184631/http://classic.austlii.edu.au/au/legis/vic/hist_act/ga189043/ |date=10 July 1890 | url-status=live }}</ref> and throughout Australia by 1912,<ref name="unsw">{{cite web |title=Platypus Conservation Initiative |url=https://www.unsw.edu.au/research/platypus-conservation-initiative/the-platypus |url-status=live |archive-url=https://web.archive.org/web/20230519032354/https://www.unsw.edu.au/research/platypus-conservation-initiative/the-platypus |archive-date=19 May 2023 |access-date=9 August 2023 |website=[[University of New South Wales]]}}</ref> until about 1950 it was still at risk of drowning in the nets of inland [[fisheries]].<ref name="CSIRO" /> The use of opera house traps for catching [[Common yabby|yabbies]] by recreational fishers is banned in the ACT, South Australia, Tasmania and Victoria, and restricted in NSW and Queensland, due to causing the drowning death of platypuses and other non-target species.<ref>[https://kb.rspca.org.au/knowledge-base/can-enclosed-yabby-traps-harm-animals-and-are-they-legal-to-use/ Can enclosed yabby traps harm animals and are they legal to use?] RSPCA Australia, 2025. Retrieved 25 April 2025.</ref> 

The [[International Union for Conservation of Nature]] recategorised its status as "near threatened" in 2016.<ref name="iucn"/> The species is protected by law, but the only state in which it is listed as endangered is South Australia, under the ''[[National Parks and Wildlife Act 1972]]''. In November 2020 a recommendation was made to list the platypus as a vulnerable species across all states<ref name="2020report">{{cite web | title=A national assessment of the conservation status of the platypus | website=[[Australian Conservation Foundation]] | url=https://www.acf.org.au/platypus_report | date=23 November 2020 | access-date=28 November 2020 | archive-date=28 November 2020 | archive-url=https://web.archive.org/web/20201128041842/https://www.acf.org.au/platypus_report | url-status=live }}</ref> with a vulnerable listing being made official in Victoria under the state's ''[[Flora and Fauna Guarantee Act 1988]]'' on 10 January 2021.<ref name="riskassessment">{{cite web |title=Platypus Risk Assessment |url=https://www.environment.vic.gov.au/__data/assets/pdf_file/0023/595040/Platypus-Risk-Assessment-Report.pdf |url-status=live |archive-url=https://web.archive.org/web/20230327161147/https://www.environment.vic.gov.au/__data/assets/pdf_file/0023/595040/Platypus-Risk-Assessment-Report.pdf |archive-date=27 March 2023 |access-date=9 August 2023 |website=[[Department of Energy, Environment and Climate Action]]}}</ref>

==== Habitat destruction ====
The platypus is not considered to be in immediate danger of extinction, because conservation measures have been successful, but it could be adversely affected by habitat disruption caused by [[dam]]s, [[irrigation]], [[pollution]], netting, and trapping.<ref>{{cite journal | last1=Stannard | first1=H.J. | last2=Wolfenden | first2=J. | last3=Old | first3=J.M. | year=2010 | title=Evaluating the capacity of constructed wetlands to sustain a captive population of Platypus (''Ornithorhynchus anatinus'') | journal=Australasian Journal of Environmental Management | volume=17 | issue=1 | pages=27–34 | doi=10.1080/14486563.2010.9725246 | bibcode=2010AuJEM..17...27S }}</ref> Reduction of watercourse flows and water levels through excessive droughts and extraction of water for industrial, agricultural, and domestic supplies are also considered a threat. The [[IUCN]] lists the platypus on its [[Red List]] as "[[Near Threatened]]"<ref name="iucn" /> as assessed in 2016, when it was estimated that numbers had reduced by about 30 percent on average since European settlement. The animal is listed as endangered in South Australia, but it is not covered at all under the federal ''[[EPBC Act]]''.<ref name=natgeog>{{cite web | title=The silent decline of the platypus, Australia's beloved oddity | website=National Geographic | first=Christie | last=Wilcox | date=29 August 2019 | url=https://www.nationalgeographic.com/animals/2019/08/common-platypus-disappearing-australia/ | access-date=12 October 2020 | archive-date=12 October 2020 | archive-url=https://web.archive.org/web/20201012141601/https://www.nationalgeographic.com/animals/2019/08/common-platypus-disappearing-australia/ | url-status=dead }}</ref><ref>{{cite web | title=EPBC Act List of Threatened Fauna | website=Species Profile and Threats Database | publisher=Australian Government. [[Department of Agriculture, Water and the Environment]] | url=https://www.environment.gov.au/cgi-bin/sprat/public/publicthreatenedlist.pl | access-date=12 October 2020 | archive-date=5 November 2020 | archive-url=https://web.archive.org/web/20201105231657/http://www.environment.gov.au/cgi-bin/sprat/public/publicthreatenedlist.pl | url-status=live }}</ref>

Researchers have worried for years that declines have been greater than assumed.<ref name=natgeog/> In January 2020, researchers from the [[University of New South Wales]] presented evidence that the platypus is at risk of [[extinction]], due to a combination of extraction of [[water resource]]s, [[land clearing]], [[climate change]] and severe [[drought]].<ref name="EA-20200121">{{cite web |author=University of New South Wales |title=Platypus on brink of extinction |url=https://www.eurekalert.org/pub_releases/2020-01/uons-pob011920.php |date=21 January 2020 |work=[[EurekAlert!]] |access-date=22 January 2020 |author-link=University of New South Wales |archive-date=13 May 2020 |archive-url=https://web.archive.org/web/20200513103618/https://www.eurekalert.org/pub_releases/2020-01/uons-pob011920.php |url-status=live }}</ref><ref name=brink2020>{{cite press release |title=Platypus on brink of extinction |url=https://www.sciencedaily.com/releases/2020/01/200121112922.htm |work=ScienceDaily |publisher=University of New South Wales |date=21 January 2020 }}</ref> The study predicted that, considering current threats, the animals' abundance would decline by 47–66% and [[metapopulation]] occupancy by 22–32% over 50 years, causing "extinction of local populations across about 40% of the range". Under projections of climate change projections to 2070, reduced habitat due to drought would lead to 51–73% reduced abundance and 36–56% reduced metapopulation occupancy within 50 years respectively. These predictions suggested that the species would fall under the "Vulnerable" classification. The authors stressed the need for national conservation efforts, which might include conducting more surveys, tracking trends, reduction of threats and improvement of river management to ensure healthy platypus habitat.<ref>{{cite journal |last1=Bino |first1=Gilad |last2=Kingsford |first2=Richard T. |last3=Wintle |first3=Brendan A. |title=A stitch in time – Synergistic impacts to platypus metapopulation extinction risk |journal=Biological Conservation |date=February 2020 |volume=242 |pages=108399 |doi=10.1016/j.biocon.2019.108399 |bibcode=2020BCons.24208399B }}</ref> Co-author Gilad Bino is concerned that the estimates of the 2016 baseline numbers could be wrong, and numbers may have been reduced by as much as half already.<ref name=natgeog/>

A November 2020 report by scientists from the [[University of New South Wales]], funded by a research grant from the [[Australian Conservation Foundation]] in collaboration with the [[World Wildlife Fund|World Wildlife Fund Australia]] and the [[Humane Society International Australia]] revealed that that platypus habitat in Australia had shrunk by 22 per cent in the previous 30 years, and recommended that the platypus should be listed as a threatened species under the ''EPBC Act''.<ref name=2020report/><ref>{{cite web | last=Cox | first=Lisa | title=Australia's platypus habitat has shrunk 22% in 30 years, report says | website=the Guardian | date=23 November 2020 | url=http://www.theguardian.com/environment/2020/nov/23/australias-platypus-habitat-has-shrunk-22-in-30-years-report-says | access-date=28 November 2020 | archive-date=28 November 2020 | archive-url=https://web.archive.org/web/20201128065816/https://www.theguardian.com/environment/2020/nov/23/australias-platypus-habitat-has-shrunk-22-in-30-years-report-says | url-status=live }}</ref> Declines in population had been greatest in NSW, in particular in the [[Murray–Darling basin]].<ref>{{cite web | title=Platypus should be listed as a threatened species: new report | website=UNSW Newsroom | publisher=[[University of New South Wales]] | date=23 November 2020 | url=https://newsroom.unsw.edu.au/news/science-tech/platypus-should-be-listed-threatened-species-new-report | access-date=28 November 2020 | archive-date=26 November 2020 | archive-url=https://web.archive.org/web/20201126093055/https://newsroom.unsw.edu.au/news/science-tech/platypus-should-be-listed-threatened-species-new-report | url-status=live | author1=z3525972 }}</ref><ref name=2020report/>

==== Disease ====
Platypuses generally suffer from few [[disease]]s in the wild; however, as of 2008 there was concern in Tasmania about the potential impacts of a disease caused by the fungus ''[[Mucor amphibiorum]]''. The disease (termed [[mucormycosis]]) affects only Tasmanian platypuses, and had not been observed in platypuses in mainland Australia. Affected platypuses can develop skin lesions or [[ulcer]]s on various parts of their bodies, including their backs, tails, and legs. Mucormycosis can kill platypuses, death arising from secondary infection and by affecting the animals' ability to maintain body temperature and forage efficiently. The Biodiversity Conservation Branch at the Department of Primary Industries and Water collaborated with NRM north and [[University of Tasmania]] researchers to determine the impacts of the disease on Tasmanian platypuses, as well as the mechanism of transmission and spread of the disease.<ref name="DPIW2">{{cite web|url=http://www.dpiw.tas.gov.au/inter.nsf/WebPages/SSKA-7AH66E?open |title=Platypus Fungal Disease |publisher=Department of Primary Industries and Water, Tasmania |date=29 August 2008 |access-date=29 February 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080307100350/http://www.dpiw.tas.gov.au/inter.nsf/WebPages/SSKA-7AH66E?open |archive-date= 7 March 2008 }}</ref>

=== Wildlife sanctuaries ===
Much of the world was introduced to the platypus in 1939 when ''[[National Geographic Magazine]]'' published an article on the platypus and the efforts to study and raise it in captivity. The latter is a difficult task, and only a few young have been successfully raised since, notably at [[Healesville Sanctuary]] in [[Victoria (Australia)|Victoria]]. The leading figure in these efforts was [[David Fleay]], who established a platypusary (a simulated stream in a tank) at the Healesville Sanctuary, where breeding was successful in 1943.<ref name="Zoos Voctoria">{{cite web| url = http://www.zoo.org.au/news/fantastic-fleay-turns-20| title = Fantastic Fleay turns 20!| access-date = 4 February 2014| date = 31 October 2013| work = Zoos Victoria| archive-url = https://web.archive.org/web/20181109084854/https://www.zoo.org.au/news/fantastic-fleay-turns-20| archive-date = 9 November 2018| url-status = dead}}</ref> In 1972, he found a dead baby of about 50 days old, which had presumably been born in captivity, at his [[David Fleay Wildlife Park|wildlife park]] at [[Burleigh Heads, Queensland|Burleigh Heads]] on the [[Gold Coast, Queensland|Gold Coast]], Queensland.<ref name="DF">{{cite web|url=http://www.epa.qld.gov.au/nature_conservation/wildlife/david_fleay_wildlife_park/50_years_wild/david_fleays_achievements/|title= David Fleay's achievements|publisher=Queensland Government|date=23 November 2003| access-date = 13 September 2006|archive-url = https://web.archive.org/web/20061002043523/http://www.epa.qld.gov.au/nature_conservation/wildlife/david_fleay_wildlife_park/50_years_wild/david_fleays_achievements/ |archive-date = 2 October 2006|url-status=dead}}</ref> Healesville repeated its success in 1998 and again in 2000 with a similar stream tank.<ref name="catalyst"/> Since 2008, platypus has bred regularly at Healesville,<ref>{{cite web| url=https://www.zoo.org.au/news/pitter-patter---platypus-twins| title=Pitter patter – Platypus twins!| publisher=Zoo Victoria| date=4 March 2013| access-date=17 August 2017| archive-url=https://web.archive.org/web/20180828052202/https://www.zoo.org.au/news/pitter-patter---platypus-twins| archive-date=28 August 2018| url-status=dead}}</ref> including second-generation (captive born themselves breeding in captivity).<ref name=PlatConservZoo>{{cite web | url=https://platypus.asn.au/conservation/zoos/ | title=Zoos | publisher=Australian Platypus Conservancy | access-date=17 August 2017 | date=22 November 2016 | archive-url=https://web.archive.org/web/20190304055829/https://platypus.asn.au/conservation/zoos/ | archive-date=4 March 2019 | url-status=dead }}</ref> [[Taronga Zoo]] in [[Sydney]] bred twins in 2003, and breeding was again successful there in 2006.<ref name="catalyst">{{cite web|url=http://www.abc.net.au/catalyst/stories/s988946.htm|title=Platypus|publisher=Catalyst|date=13 November 2003|access-date=13 September 2006|archive-date=23 July 2011|archive-url=https://web.archive.org/web/20110723232610/http://www.abc.net.au/catalyst/stories/s988946.htm|url-status=live}}</ref>

=== Captivity ===
As of 2019, the only platypuses in captivity outside of Australia are in the [[San Diego Zoo Safari Park]] in the [[U.S. state]] of [[California]].<ref>{{cite web|url=https://www.kpbs.org/news/2019/nov/22/platypus-display-san-diego/|title=Rare Platypus On Display At San Diego Zoo Safari Park|last=Anderson|first=Erik|date=22 November 2019|website=KPBS Public Media|language=en|access-date=29 December 2019|quote=The animals are the only platypuses on display outside of their native country.|archive-date=13 May 2020|archive-url=https://web.archive.org/web/20200513103631/https://www.kpbs.org/news/2019/nov/22/platypus-display-san-diego/|url-status=live}}</ref><ref>{{cite web|url=https://animals.sandiegozoo.org/animals/platypus|title=Platypus {{!}} San Diego Zoo Animals & Plants|website=animals.sandiegozoo.org|access-date=29 December 2019|archive-date=25 July 2020|archive-url=https://web.archive.org/web/20200725024623/https://animals.sandiegozoo.org/animals/platypus|url-status=live}}</ref> Three attempts were made to bring the animals to the [[Bronx Zoo]], in 1922, 1947, and 1958. Of these, only two of the three animals introduced in 1947, [[Penelope (platypus)|Penelope]] and Cecil,<ref>{{Cite magazine |date=19 August 1957 |title=Animals: End of the Affair |url=http://www.time.com/time/magazine/article/0%2C9171%2C809719%2C00.html |archive-url=https://web.archive.org/web/20070616062446/http://www.time.com/time/magazine/article/0,9171,809719,00.html |archive-date=16 June 2007 |magazine=[[Time (magazine)|Time]]}}</ref> lived longer than eighteen months.<ref>{{cite book | author = Lee S. Crandall | title = The Management of Wild Mammals in Captivity | publisher = University of Chicago Press | date = 1964}}</ref>

== Human interactions ==
=== Usage ===
[[Aboriginal Australians]] used to hunt platypuses for food (their fatty tails being particularly nutritious), while, after colonisation, Europeans hunted them for fur from the late 19th century until 1912, when it was prohibited by law.<ref name=1912article>{{cite web | title=Protecting Wild Animals | work=[[The Advertiser (Adelaide)]] | url=https://trove.nla.gov.au/newspaper/article/5338401 | access-date=9 August 2023 | archive-date=9 August 2023 | archive-url=https://web.archive.org/web/20230809172243/https://trove.nla.gov.au/newspaper/article/5338401 |date=27 September 1912 | url-status=live }}</ref> In addition, European researchers captured and killed platypus or removed their eggs, partly in order to increase scientific knowledge, but also to gain prestige and outcompete rivals from different countries.<ref name=2020report/>

=== Cultural references ===
The platypus has been a subject in the [[Dreamtime]] stories of [[Aboriginal Australians]], some of whom believed the animal was a hybrid of a duck and a [[Rakali|water rat]].<ref name=Gadi>{{cite book|author1=McKay, Helen F. |author2=McLeod, Pauline E. |author3=Jones, Francis F. |author4=Barber, June E. |year=2001|title=Gadi Mirrabooka: Australian Aboriginal Tales from the Dreaming|publisher=Libraries Unlimited|isbn=978-1563089237}}</ref>{{rp|57–60}}

According to one story of the upper [[Darling River]],<ref name=2020report/> the major animal groups, the land animals, water animals and birds, all competed for the platypus to join their respective groups, but the platypus ultimately decided to not join any of them, feeling that he did not need to be part of a group to be special,<ref name=Gadi/>{{rp|83–85}} and wished to remain friends with all of those groups.<ref name=2020report/> Another Dreaming story emanate of the upper Darling tells of a young duck which ventured too far, ignoring the warnings of her tribe, and was kidnapped by a large water-rat called Biggoon. After managing to escape after some time, she returned and laid two eggs which hatched into strange furry creatures, so they were all banished and went to live in the mountains.<ref name=2020report/>

The platypus is also used by some Aboriginal peoples as a [[totem]], which is to them "a natural object, plant or animal that is inherited by members of a clan or family as their spiritual emblem", and the animal holds special meaning as a totem animal for the [[Wadi Wadi]] people, who live along the [[Murray River]]. Because of their cultural significance and importance in [[connection to country]], the platypus is protected and conserved by these Indigenous peoples.<ref name=2020report/>

The platypus has often been used as a symbol of Australia's [[cultural identity]]. In the 1940s, live platypuses were given to allies in the [[Second World War]], in order to strengthen ties and boost morale.<ref name=2020report/>

Platypuses have been used several times as mascots: Syd the platypus was one of the three mascots chosen for the [[2000 Summer Olympics|Sydney 2000 summer Olympics]] along with an echidna and a [[kookaburra]],<ref>{{cite web|url=http://en.beijing2008.com/31/87/article211928731.shtml |title=A Brief History of the Olympic and Paralympic Mascots |publisher=Beijing2008 |date=5 August 2004 |access-date=25 October 2006 |url-status=dead |archive-url=https://web.archive.org/web/20080621113930/http://en.beijing2008.com/31/87/article211928731.shtml |archive-date=21 June 2008 }}</ref> Expo Oz the platypus was the mascot for [[World Expo 88]], which was held in [[Brisbane]] in 1988,<ref>{{cite web|url=http://www.foundationexpo88.org/aboutcontents.html |title=About World Expo '88 |publisher=Foundation Expo '88 |year=1988 |access-date=17 December 2007 |url-status=dead |archive-url=https://web.archive.org/web/20131219232431/http://www.foundationexpo88.org/aboutcontents.html |archive-date=19 December 2013 }}</ref> and Hexley the platypus is the mascot for the [[Darwin (operating system)|Darwin]] operating system, the [[BSD]]-based core of [[macOS]] and other operating systems from [[Apple Inc.]]<ref>{{cite web|url=http://www.hexley.com/|title=The Home of Hexley the Platypus|access-date=25 October 2006|archive-date=13 February 2011|archive-url=https://web.archive.org/web/20110213095652/http://www.hexley.com/|url-status=live}}</ref>

Since the introduction of [[decimal currency]] to [[Australia]] in 1966, the embossed image of a platypus, designed and sculpted by [[Stuart Devlin]], has appeared on the reverse (tails) side of the [[Australian twenty-cent coin|20-cent coin]].<ref>{{cite web|url=https://www.ramint.gov.au/twenty-cents|title=Circulating coins: Twenty Cents|date=8 January 2016 |publisher=Royal Australian Mint|access-date=12 September 2020|archive-date=19 March 2021|archive-url=https://web.archive.org/web/20210319031414/https://www.ramint.gov.au/twenty-cents|url-status=live}}</ref> The platypus has frequently appeared in Australian postage stamps, most recently the 2015 "Native Animals" series and the 2016 "Australian Animals Monotremes" series.<ref>{{cite web|url=https://australiapostcollectables.com.au/stamp-issues/2015-01-13_native-animals.html|title=Native Animals - Issue Date 13 January 2015|publisher=Australia Post Collectables|access-date=12 September 2020|archive-date=25 January 2021|archive-url=https://web.archive.org/web/20210125223959/https://australiapostcollectables.com.au/stamp-issues/2015-01-13_native-animals.html|url-status=live}}</ref><ref>{{cite web|url=https://australiapostcollectables.com.au/stamp-issues/australian-animals-monotremes.html|title=Australian Animals Monotremes – Issue Date 26 September 2016|publisher=Australia Post Collectables|access-date=12 September 2020|archive-date=26 January 2021|archive-url=https://web.archive.org/web/20210126001019/https://australiapostcollectables.com.au/stamp-issues/australian-animals-monotremes.html|url-status=live}}</ref>

In the American animated series ''[[Phineas and Ferb]]'', the [[title character]]s own a pet bluish-green platypus named [[Perry the Platypus|Perry]] who, unknown to them, is a secret agent. Such choices were inspired by media underuse, as well as to exploit the animal's striking appearance;<ref name="QA">{{cite news|url=https://www.hollywoodreporter.com/news/disney-ferb-pickup-major-push-85063|title=Disney gives 'Ferb' pickup, major push – Q&A: Dan Povenmire|date=7 June 2009|work=The Hollywood Reporter|access-date=5 March 2017|archive-date=20 June 2018|archive-url=https://web.archive.org/web/20180620203720/https://www.hollywoodreporter.com/news/disney-ferb-pickup-major-push-85063|url-status=live}}</ref> additionally, show creator [[Dan Povenmire]], who also wrote the character's theme song, said that its opening lyrics are based on the introductory sentence of the Platypus article on Wikipedia, copying the "semiaquatic egg-laying mammal" phrase word for word and appending the phrase "of action";<ref>{{Citation|title="Perry the Platypus" Live at Musi-Cal| date=9 August 2016 |url=https://www.youtube.com/watch?v=dnGX-wucxQs|language=en|access-date=23 March 2021|archive-date=2 January 2021|archive-url=https://web.archive.org/web/20210102002447/https://www.youtube.com/watch?v=dnGX-wucxQs|url-status=live}}</ref> however, the article did not include "egg-laying mammal" in the lead sentence until 2014, several years after the song released. As a character, Perry has been well received by both fans and critics.<ref name="star">{{cite web|url=https://variety.com/2009/digital/features/phineas-star-perry-makes-mark-on-auds-1118011690/|title='Phineas' star Perry makes mark on auds|author=Littleton, Cynthia|date=20 November 2009|work=[[Variety (magazine)|Variety]]|access-date=26 November 2009|archive-date=2 December 2009|archive-url=https://web.archive.org/web/20091202110736/http://www.variety.com/article/VR1118011690.html?categoryid=1050&cs=1|url-status=live}}</ref><ref>{{cite magazine|url=https://www.pastemagazine.com/blogs/lists/2009/03/7-reasons-why-phineas-and-ferb-is-the-best-kids-sh.html|title=Five Reasons Why ''Phineas and Ferb'' is the Best Kids Show on TV|magazine=[[Paste (magazine)|Paste]]|author=Jackson, John|date=31 March 2009|access-date=25 November 2009|archive-date=3 October 2019|archive-url=https://web.archive.org/web/20191003091539/https://www.pastemagazine.com/blogs/lists/2009/03/7-reasons-why-phineas-and-ferb-is-the-best-kids-sh.html|url-status=live}}</ref> Coincidentally, real platypuses show a similar cyan colour when seen under ultraviolet lighting.<ref>{{cite journal |last1=Anich |first1=Paula Spaeth |last2=Anthony |first2=Sharon |last3=Carlson |first3=Michaela |last4=Gunnelson |first4=Adam |last5=Kohler |first5=Allison M. |last6=Martin |first6=Jonathan G. |last7=Olson |first7=Erik R. |title=Biofluorescence in the platypus (''Ornithorhynchus anatinus'') |journal=Mammalia |date=26 March 2021 |volume=85 |issue=2 |pages=179–181 |doi=10.1515/mammalia-2020-0027 }}</ref>

<gallery mode="packed" heights="180px">
Platypus cape unknown tasmania.jpg|Platypus fur cape made in 1890, now in the National Gallery of Victoria
"Nam Sang Woo Safety Matches" platypus matchbox label art - from, Collectie NMvWereldculturen, TM-6477-76, Etiketten van luciferdoosjes, 1900-1949 (cropped).jpg|Early 20th-century [[matchbox]] label
Australianstamp 1551.jpg|9d postage stamp from 1937
</gallery>

== See also ==
* [[Henry Burrell]]
*[[Ellis Stanley Joseph#Platypus (1922)|Ellis Joseph]]
* [[Fauna of Australia]]

== Footnotes ==
{{Notelist|1}}

== Citations ==
{{Reflist}}

== References ==
=== Books ===
* {{cite encyclopedia |last=Augee |first=Michael L. |encyclopedia=World Book Encyclopedia |title=Platypus |year=2001 }}
* {{cite book |author=Burrell, Harry |title=The Platypus |publisher=Rigby |location=Adelaide SA |year=1974 |isbn=978-0-85179-521-8 }}
* {{cite book |author=Fleay, David H. |title=Paradoxical Platypus: Hobnobbing with Duckbills |publisher=Jacaranda Press |year=1980 |isbn=978-0-7016-1364-8 |url=https://books.google.com/books?id=IaIKAQAAMAAJ}}
* {{cite book |author=Grant, Tom |title=The platypus: a unique mammal |publisher=University of New South Wales Press |location=Sydney |year=1995 |isbn=978-0-86840-143-0 |url=https://books.google.com/books?id=FASJWgDhxIsC}}
* {{cite book |author=Griffiths, Mervyn |title=The Biology of the Monotremes |publisher=Academic Press |year=1978 |isbn=978-0-12-303850-0 |url=https://books.google.com/books?id=1KTwAAAAMAAJ}}
* {{cite encyclopedia |editor1=Hutch, Michael |editor2=McDade, Melissa C. |encyclopedia=Grzimek's Animal Life Encyclopedia |title= Grzimek's Animal Life Encyclopedia: Lower metazoans and lesser deuterosomes|year=2004 |publisher=Gale |volume=12: ''Mammals III'' |oclc=1089554968 |isbn=9780787657772}}
* {{cite book |author=Moyal, Ann Mozley |author-link=Ann Moyal |title=Platypus: The Extraordinary Story of How a Curious Creature Baffled the World |publisher=The Johns Hopkins University Press |location=Baltimore |year=2004 |isbn=978-0-8018-8052-0 |url=https://books.google.com/books?id=5DkezNMhSTYC}}
* {{cite book|first1=Ronald |last1=Strahan|first2=Steve |last2=Van Dyck|title=Mammals of Australia |edition=3rd |url=https://books.google.com/books?id=N3tFAQAAIAAJ |date=April 2006|publisher=New Holland|isbn=978-1-877069-25-3}}

=== Documentaries ===
* {{Cite episode|title=Southern Exposure |url=http://www.abc.net.au/storm/exposure/default.htm |series=Eye of the Storm |network=[[Australian Broadcasting Corporation]] |year=2000 |url-status=dead |archive-url=https://web.archive.org/web/20130507073318/http://www.abc.net.au/storm/exposure/default.htm |archive-date=7 May 2013 }} DVD [[EAN 13|EAN]] 9398710245592
* {{Cite episode|title=El Niño |url=http://www.abc.net.au/storm/nino/default.htm |series=Eye of the Storm  |year=2000 |url-status=dead |archive-url=https://web.archive.org/web/20130228154105/http://www.abc.net.au/storm/nino/default.htm |archive-date=28 February 2013 }}

== External links ==
* [https://www.biodiversitylibrary.org/name/Ornithorhynchus_anatinus Biodiversity Heritage Library bibliography] for ''Ornithorhynchus anatinus''
* [https://web.archive.org/web/20190910215138/http://platypusfacts.net/ Platypus facts] (archived 10 September 2019)
* View the [http://www.ensembl.org/Ornithorhynchus_anatinus/Info/Index/ platypus genome] in [[Ensembl]]
* [https://www.pbs.org/video/the-platypus-guardian-axzeo8/ PBS Nature "The Platypus Guardian"]

{{Mammaliaformes|Y.|state=autocollapse}}
{{Monotremata}}
{{Taxonbar|from=Q15343}}

[[Category:Ornithorhynchidae]]
[[Category:Monotremes]]
[[Category:Semiaquatic mammals]]
[[Category:Electroreceptive animals]]
[[Category:Mammals of New South Wales]]
[[Category:Mammals of Queensland]]
[[Category:Mammals of South Australia]]
[[Category:Mammals of Tasmania]]
[[Category:Mammals of Victoria (state)]]
[[Category:Venomous mammals]]
[[Category:Articles containing video clips]]
[[Category:Extant Pliocene first appearances]]
[[Category:Quaternary animals of Australia]]
[[Category:Quaternary animals of Oceania]]
[[Category:Mammals described in 1799]]
[[Category:Mammal genera with one living species]] 
[[Category:Taxa named by George Shaw]]
[[Category:Symbols of New South Wales]]