{{Short description|List of microorganisms}} The '''smallest organisms''' found on Earth can be determined according to various aspects of organism size, including volume, mass, height, length, or genome size.
Given the incomplete nature of scientific knowledge, it is likely that the smallest organism is undiscovered. Furthermore, there is some debate over the definition of life, and what entities qualify as organisms; consequently the smallest known organisms (microrganisms) may be nanobes that can be 20 nanometers long.
== Microorganisms ==
=== Obligate endosymbiotic bacteria === The genome of ''Nasuia deltocephalinicola'', a symbiont of the European pest leafhopper, ''Macrosteles quadripunctulatus'', consists of a circular chromosome of 112,031 base pairs.<ref>{{cite journal|last1=Bennett|first1=Gordon M.|last2=Abbà|first2=Simona|last3=Kube|first3=Michael|last4=Marzachì|first4=Cristina|title=Complete Genome Sequences of the Obligate Symbionts 'Candidatus Sulcia muelleri' and "Ca. Nasuia deltocephalinicola" from the Pestiferous Leafhopper Macrosteles quadripunctulatus (Hemiptera: Cicadellidae)|journal=Genome Announcements|date=25 February 2016|volume=4|issue=1|pages=e01604–15|doi=10.1128/genomeA.01604-15|language=en|issn=2169-8287|pmc=4722273|pmid=26798106}}</ref>
The genome of ''Nanoarchaeum equitans'' is 491 Kbp long.<ref>{{cite journal | last1=Waters | first1=Elizabeth | last2=Hohn | first2=Michael J. | last3=Ahel | first3=Ivan | last4=Graham | first4=David E. | last5=Adams | first5=Mark D. | last6=Barnstead | first6=Mary | last7=Beeson | first7=Karen Y. | last8=Bibbs | first8=Lisa | last9=Bolanos | first9=Randall | last10=Keller | first10=Martin | last11=Kretz | first11=Keith | last12=Lin | first12=Xiaoying | last13=Mathur | first13=Eric | last14=Ni | first14=Jingwei | last15=Podar | first15=Mircea | last16=Richardson | first16=Toby | last17=Sutton | first17=Granger G. | last18=Simon | first18=Melvin | last19=Söll | first19=Dieter | last20=Stetter | first20=Karl O. | last21=Short | first21=Jay M. | last22=Noordewier | first22=Michiel | title=The genome of Nanoarchaeum equitans: Insights into early archaeal evolution and derived parasitism | journal=Proceedings of the National Academy of Sciences | volume=100 | issue=22 | date=2003-10-17 | issn=0027-8424 | doi=10.1073/pnas.1735403100 | doi-access=free | pages=12984–12988| pmid=14566062 | pmc=240731 | bibcode=2003PNAS..10012984W }}</ref>
=== ''Pelagibacter ubique'' === [[File:Pelagibacter.jpg|thumb|Electron micrograph of the bacterium ''Pelagibacter ubique'']] ''Pelagibacter ubique'' is one of the smallest known free-living bacteria, with a length of {{cvt|370|to|890|nm|mm}} and an average cell diameter of {{cvt|120|to|200|nm|mm}}. They also have the smallest free-living bacterium genome: 1.3 Mbp, 1354 protein genes, 35 RNA genes. They are one of the most common and smallest organisms in the ocean, with their total weight exceeding that of all fish in the sea.<ref>{{cite web|url=https://microbewiki.kenyon.edu/index.php/Pelagibacter_ubique|title=Pelagibacter ubique - microbewiki|website=microbewiki.kenyon.edu|access-date=19 April 2018}}</ref>
=== ''Mycoplasma genitalium'' === ''Mycoplasma genitalium'', a parasitic bacterium which lives in the primate bladder, waste disposal organs, genital, and respiratory tracts, is thought to be the smallest known organism capable of independent growth and reproduction. With a size of approximately 200 to 300 nm, ''M. genitalium'' is an ultramicrobacterium, smaller than other small bacteria, including rickettsia and chlamydia. However, the vast majority of bacterial strains have not been studied, and the marine ultramicrobacterium ''Sphingomonas'' sp. strain RB2256 is reported to have passed through a {{cvt|220|nm|mm}} ultrafilter. A complicating factor is nutrient-downsized bacteria, bacteria that become much smaller due to a lack of available nutrients.<ref>{{cite web|url=http://www.madsci.org/posts/archives/sep2001/1001464156.Gb.r.html |title=Re: What is the smallest living thing? |publisher=Madsci.org |access-date=2013-10-03}}</ref>
=== ''Nanoarchaeum'' === [[File:Urzwerg.jpg|thumb|upright|Two ''Nanoarchaeum equitans'' and archaeon host, ''Ignicoccus'']]
''Nanoarchaeum equitans'' is a species of microbe {{cvt|200|to|500|nm|mm}} in diameter. It was discovered in 2002 in a hydrothermal vent off the coast of Iceland by Karl Stetter. A thermophile that grows in near-boiling temperatures, ''Nanoarchaeum'' appears to be an obligatory symbiont on the archaeon ''Ignicoccus''; it must be in contact with the host organism to survive. ''Guinness World Records'' recognizes ''Nanoarchaeum equitans'' as the smallest living organism.<ref>{{cite web | title=Smallest living organism | website=Guinness World Records | date=2011-01-25 | url=https://www.guinnessworldrecords.com/world-records/smallest-living-organism- | access-date=2024-12-04}}</ref>
=== Single-celled eukaryotes (protists) === Prasinophyte algae of the genus ''Ostreococcus'' are the smallest free-living eukaryote. The single cell of an ''Ostreococcus'' measures {{cvt|800|nm|mm}} across.<ref name="Courties 94" >{{cite journal|vauthors=Courties C, Vaquer A, Troussellier M, Lautier J, Chrétiennot-Dinet MJ, Neveux J, Machado C, Claustre H|year=1994|title=Smallest eukaryotic organism|journal=Nature|volume=370|issue=255|page=255 |doi=10.1038/370255a0|s2cid=4321127|doi-access=free|bibcode=1994Natur.370..255C }}</ref> ====Heliozoa==== The ''Erebor'' lineage of ''Microheliella maris'' is the smallest known heliozoan with an average cell body diameter of 2.56 μm.<ref name="Shishkin 2021">{{cite journal|vauthors=Shishkin Y, Drachko D, Zlatogursky VV|title=The smallest known heliozoans are the Erebor lineage (nom. clad. n.) inside Microheliella maris (Eukaryota, Diaphoretickes), with the amendation of M. maris diagnosis and description of Berkeleyaesol magnus gen. nov., comb. nov. (Eukaryota, incertae sedis)|journal=Int J Syst Evol Microbiol|date=April 2021|volume=71|issue=4|doi=10.1099/ijsem.0.004776|pmid=33886450|url=https://www.microbiologyresearch.org/docserver/fulltext/ijsem/71/4/ijsem004776.pdf|access-date=2024-06-13}}</ref>
==== Diatoms ==== The smallest diatoms with diameters as small as 1.9 μm can be found in the genera ''Mediolabrus'' and ''Minidiscus.''<ref>{{Cite web |title=Home - Minidiscus variabilis CCMP495 v1.0 |url=https://phycocosm.jgi.doe.gov/Mintr2/Mintr2.home.html |access-date=2025-04-26 |website=phycocosm.jgi.doe.gov}}</ref><ref>{{Cite journal |last1=Jewson |first1=David |last2=Kuwata |first2=Akira |last3=Cros |first3=Lluïsa |last4=Fortuño |first4=José Manuel |last5=Estrada |first5=Marta |date=2016-09-30 |title=Morphological adaptations to small size in the marine diatom Minidiscus comicus |url=https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/1660 |journal=Scientia Marina |volume=80 |issue=S1 |pages=89–96 |doi=10.3989/scimar.04331.06C |bibcode=2016ScMar..80S..89J |issn=1886-8134|hdl=10261/138162 |hdl-access=free }}</ref> ''Mediolabrus comicus'' is the smallest known marine diatom.<ref>{{Cite journal |last1=Arsenieff |first1=Laure |last2=Le Gall |first2=Florence |last3=Rigaut-Jalabert |first3=Fabienne |last4=Mahé |first4=Frédéric |last5=Sarno |first5=Diana |last6=Gouhier |first6=Léna |last7=Baudoux |first7=Anne-Claire |last8=Simon |first8=Nathalie |date=2020 |title=Diversity and dynamics of relevant nanoplanktonic diatoms in the Western English Channel |journal=The ISME Journal |volume=14 |issue=8 |pages=1966–1981 |doi=10.1038/s41396-020-0659-6 |issn=1751-7370 |pmc=7367886 |pmid=32350410|bibcode=2020ISMEJ..14.1966A }}</ref>
=== Viruses === Some biologists consider viruses to be non-living because they lack a cellular structure and cannot metabolize or reproduce by themselves, requiring a host cell to replicate and synthesize new products. Some hold that, because viruses do have genetic material and can employ the metabolism of their host, they can be considered organisms. Also, an emerging concept that is gaining traction among some virologists is that of the ''virocell'', in which the actual phenotype of a virus is the infected cell, and the virus particle (or ''virion'') is merely a reproductive or dispersal stage, much like pollen or a spore.<ref name="Forterre 2012">{{cite journal |author1=P. Forterre |title=The virocell concept and environmental microbiology|journal=The ISME Journal|year=2012|doi=10.1038/ismej.2012.110 |volume=7 |issue=2|pages=233–236|pmc=3554396 |pmid=23038175}}</ref>
The smallest viruses in terms of genome size are single-stranded DNA (ssDNA) viruses. Perhaps the most famous is the bacteriophage Phi-X174 with a genome size of 5,386 nucleotides.<ref>{{cite journal |doi=10.1038/265687a0 |title=Nucleotide sequence of bacteriophage ΦX174 DNA |year=1977 |last1=Sanger |first1=F. |last2=Air |first2=G. M. |last3=Barrell |first3=B. G. |last4=Brown |first4=N. L. |last5=Coulson |first5=A. R. |last6=Fiddes |first6=J. C. |last7=Hutchison |first7=C. A. |last8=Slocombe |first8=P. M. |last9=Smith |first9=M. |journal=Nature |volume=265 |issue=5596 |pages=687–95 |pmid=870828|bibcode = 1977Natur.265..687S |s2cid=4206886 }}</ref> However, some ssDNA viruses can be even smaller. For example, Porcine circovirus type 1 has a genome of 1,759 nucleotides<ref>{{cite journal |title=APorcine circoviruses--small but powerful |vauthors=Finsterbusch T, Mankertz A |year=2009 | journal = Virus Research | volume = 143 | issue = 2 | pages = 177–183 | pmid=19647885 | doi=10.1016/j.virusres.2009.02.009}}</ref> and a capsid diameter of {{cvt|17|nm|mm}}.<ref>[http://phene.cpmc.columbia.edu/ICTVdB/WWW/16002005.htm ICTVdB Virus Description – 00.016.0.01.005. Porcine circovirus 2<!-- Bot generated title -->] {{webarchive |url=https://web.archive.org/web/20070704162350/http://phene.cpmc.columbia.edu/ICTVdB/WWW/16002005.htm |date=July 4, 2007 }}</ref> As a whole, the viral family geminiviridae is about {{cvt|30|nm|mm}} in length. However, the two capsids making up the virus are fused; divided, the capsids would be {{cvt|15|nm|mm}} in length. Other environmentally characterized ssDNA viruses such as CRESS DNA viruses, among others, can have genomes that are considerably less than 2,000 nucleotides.<ref name="Rosario 2015">{{cite journal |author1=K. Rosario |author2=R.O. Schenck |author3=R.C. Harbeitner |author4=S.N. Lawler |author5=M. Breitbart |title=Novel circular single-stranded DNA viruses identified in marine invertebrates reveal high sequence diversity and consistent predicted intrinsic disorder patterns within putative structural proteins |journal=Frontiers in Microbiology|year=2015|doi=10.3389/fmicb.2015.00696 |volume=6 |page=696 |pmc=4498126 |pmid=26217327|doi-access=free }}</ref><ref name="Labonte 2013">{{cite journal |author1=J.M. Labonté |author2=C.A. Suttle|title=Previously unknown and highly divergent ssDNA viruses populate the oceans|journal=The ISME Journal|year=2013|doi=10.1038/ismej.2013.110 |volume=7 |issue=11|pages=2169–2177|pmc=3806263 |pmid=23842650|bibcode=2013ISMEJ...7.2169L }}</ref>
The smallest RNA virus in terms of genome size is phage BZ13 strain T72 at 3,393 nucleotides length.<ref>{{cite web |url=https://www.ncbi.nlm.nih.gov/nuccore/FJ483838 | title= Enterobacteria phage BZ13 strain T72, complete genome |year=2008}}</ref> Viruses using both DNA and RNA in their replication (retroviruses) range in size from 7,040 to 12,195 nucleotides.<ref>{{cite book |section=Table 2: Sizes of Retroviral LTR Components (U3-R-U5) and Genomes |title=Retroviruses |veditors=Coffin JM, Hughes SH, Varmus HE | publisher=Cold Spring Harbor Laboratory Press | date=1997 | isbn=0-87969-571-4 |section-url=https://www.ncbi.nlm.nih.gov/books/NBK19417/table/A7789/}}</ref> The smallest double-stranded DNA viruses are the hepadnaviruses such as hepatitis B, at 3.2 kb and {{cvt|42|nm|mm}}; parvoviruses have smaller capsids, at {{cvt|18|-|26|nm|mm}}, but larger genomes, at 5 kb. It is important to consider other self-replicating genetic elements, such as obelisks, ribozymes, satelliviruses and viroids.{{cn|date=March 2024}}
== Animals (Animalia) == Several species of Myxozoa (obligately parasitic cnidarians) never grow larger than {{cvt|20|μm|mm}}.<ref>Fiala, Ivan. 2008. Myxozoa. Version 10 July 2008 (under construction). http://tolweb.org/Myxozoa/2460/2008.07.10 in The Tree of Life Web Project, http://tolweb.org/</ref> One of the smallest species (''Myxobolus shekel'') is no more than {{cvt|8.5|μm|mm}} when fully grown, making it the smallest known animal.<ref>{{cite journal|title=Two new species of Myxobolus (Myxozoa: Myxosporea: Bivalvulida) infecting an Indian major carp and a cat fish in wetlands of Punjab, India | pmc=3235390 | pmid=23024499 | doi=10.1007/s12639-011-0061-4 | volume=35 | year=2011 | journal=J Parasit Dis | pages=169–76 | last1 = Kaur | first1 = H | last2 = Singh | first2 = R| issue=2 }}</ref>{{failed verification|date=December 2025}}
=== Molluscs (Mollusca) === ==== Bivalvia ==== The shell of the nut clam ''Condylonucula maya'' grows {{cvt|0.54|mm}} long.<ref>{{cite journal |last1=Abele |first1=Doris |last2=Brey |first2=Thomas |last3=Philipp |first3=Eva |title=Part N, Revised, Volume 1, Chapter 7: Ecophysiology of Extant Marine Bivalvia|journal= Treatise Online |date=15 February 2017 |url=https://journals.ku.edu/treatiseonline/article/view/6583 |doi=10.17161/to.v0i0.6583|doi-access=free }}</ref>
==== Gastropods (Gastropoda) ==== [[File:Ammonicera minortalis (10.3897-zookeys.779.24562) Figure 4 (cropped).jpg|thumb|''Ammonicera minortalis'']] The smallest water snail (of all snails) is ''Ammonicera minortalis'' in North America, originally described from Cuba. It measures {{cvt|0.32|to|0.46|mm}}.<ref>{{cite journal|last1=Páll-Gergely|first1=Barna|last2=Hunyadi|first2=András|last3=Jochum|first3=Adrienne|last4=Asami|first4=Takahiro|title=Seven new hypselostomatid species from China, including some of the world's smallest land snails (Gastropoda, Pulmonata, Orthurethra)|journal=ZooKeys|date=28 September 2015|issue=523|pages=31–62|doi=10.3897/zookeys.523.6114|pmid=26478698|pmc=4602296|doi-access=free|bibcode=2015ZooK..523...31P }}</ref><ref>{{cite news|last1=Sankar-Gorton|first1=Eliza|title=Newly Discovered Land Snail Is The Tiniest In The World|url=https://www.huffpost.com/entry/new-land-snail-tiniest-in-the-world_n_563907f9e4b079a43c04dfe2|access-date=9 November 2015|work=HuffPost|date=4 November 2015}}</ref>
The smallest land snail is ''Acmella nana''. Discovered in Borneo, and described in November 2015, it measures {{cvt|0.7|mm}}.<ref>{{cite news|last1=Geggel|first1=Laura|title=Micro Mollusk Breaks Record for World's Tiniest Snail|url=http://www.livescience.com/52664-borneo-smallest-snail.html|access-date=8 November 2015|work=LiveScience|date=2 November 2015}}</ref> The previous record was that of ''Angustopila dominikae'' from China, which was reported in September 2015. This snail measures {{cvt|0.86|mm}}.<ref>{{cite journal|last1=Páll-Gergely|first1=Barna|last2=Hunyadi|first2=András|last3=Jochum|first3=Adrienne|last4=Asami|first4=Takahiro|title=Seven new hypselostomatid species from China, including some of the world's smallest land snails (Gastropoda, Pulmonata, Orthurethra)|journal=ZooKeys|year=2015|issue=523|pages=31–62|doi=10.3897/zookeys.523.6114|pmid=26478698|pmc=4602296|doi-access=free|bibcode=2015ZooK..523...31P }}</ref>
==== Cephalopods (Cephalopoda) ==== {{further|Cephalopod size}} ''Maximites'' was the smallest known ammonoid. Adult specimens reached only {{cvt|10|mm}} in shell diameter.<ref>{{cite book |vauthors=Nishiguchi MK, Mapes R |date=2008 |url=https://bobtailsquid.ink/wp-content/uploads/2020/05/Nish2008_Book_PhylEvolMolusca_Cephlopoda.pdf |chapter=Cephalopoda |veditors=Ponder W, Lindberg D |title=Phylogeny and Evolution of the Mollusca |publisher=University of California Press |pages=162–199}}</ref>
=== Arthropods (Arthropoda) === The smallest arthropods are mites ''Cochlodispus minimus'' of the family Microdispidae. The body length of the smallest measured individual was {{cvt|79|μm|mm}}.<ref>{{Cite journal|last1=Huber|first1=John|last2=Noyes|first2=John|date=2013-04-24|title=A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods|url=https://jhr.pensoft.net/article/1635/|journal=Journal of Hymenoptera Research|language=en|volume=32|pages=17–44|doi=10.3897/jhr.32.4663|issn=1314-2607|doi-access=free}}</ref> ==== Crustaceans (Crustacea) ==== The smallest crustaceans belong to the class Tantulocarida. The single smallest species may be ''Tantulacus dieteri'', with a total body length of only {{convert|85|um}}.<ref>{{cite journal |title=Tantulocarida (Crustacea) of the Southern Ocean deep sea, and the description of three new species of ''Tantulacus'' Huys, Andersen & Kristensen, 1992|author=Inga Mohrbeck |author2=Pedro Martínez Arbizu |author3=Thomas Glatzel |name-list-style=amp |journal=Systematic Parasitology |volume=77 |issue=2 |date=October 2010 |pages=131–151 |doi=10.1007/s11230-010-9260-0|pmid=20852984 }}</ref> Another candidate is ''Stygotantulus stocki'', with a length of {{convert|94|um}}.<ref name="M&D">{{cite book|url=http://atiniui.nhm.org/pdfs/3839/3839.pdf |title=An Updated Classification of the Recent Crustacea |author=Joel W. Martin |author2=George E. Davis |name-list-style=amp |year=2001 |pages=132 pp |publisher=Natural History Museum of Los Angeles County |archive-url=https://web.archive.org/web/20081010140511/http://atiniui.nhm.org/pdfs/3839/3839.pdf |archive-date=October 10, 2008}}</ref>
==== Arachnids (Arachnida) ==== * There is a debate about which spider is smallest. According to ''Guinness World Records'', "Two contenders are from the Symphytognathidae genus ''Patu'': males of ''Patu digua'' described in Colombia had a body length of {{convert|0.37|mm|in|abbr=off}}, while the Samoan moss spider (''P. marplesi'') could be as small as {{convert|0.4|mm|in|abbr=off}} long." Other possible smallest spider species are the Frade cave spider known as ''Anapistula ataecina,'' and the dwarf orb weaver (''Anapistula caecula''), the females of which are {{cvt|0.43|mm}} and {{cvt|0.48|mm}} respectively. Males of both species are potentially smaller than the females, but no male ''A. ataecina or A. caecula'' have been measured yet.<ref name=":0">{{Cite web |title=Smallest spider |url=https://www.guinnessworldrecords.com/world-records/smallest-spider/?fb_comment_id=652554088203316_761224827336241 |access-date=2021-04-16 |website=Guinness World Records |language=en-GB}}</ref> * ''Cochlodispus minimus'' is the smallest mite. An adult individual measured with a body length of {{cvt|79|μm|mm}}.<ref>{{Cite journal|last1=Huber|first1=John|last2=Noyes|first2=John|date=2013-04-24|title=A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods|url=https://jhr.pensoft.net/article/1635/|journal=Journal of Hymenoptera Research|language=en|volume=32|pages=17–44|doi=10.3897/jhr.32.4663|issn=1314-2607|doi-access=free}}</ref>
==== Insects (Insecta) ==== * Adult males of the parasitic wasp ''Dicopomorpha echmepterygis'' can be as small as {{cvt|139|μm|mm}} long, smaller than some species of protozoa (single-cell creatures); females are 40% larger.<ref>{{cite web |url=http://entnemdept.ifas.ufl.edu/walker/ufbir/chapters/chapter_38.shtml |title=University of Florida Book of Insect Records |publisher=Entnemdept.ifas.ufl.edu |date=1998-04-17 |access-date=2013-10-03 |archive-url=https://web.archive.org/web/20131005013854/http://entnemdept.ifas.ufl.edu/walker/ufbir/chapters/chapter_38.shtml |archive-date=2013-10-05 }}</ref> ''Megaphragma caribea'' from Guadeloupe, measuring {{cvt|170|μm|mm}} long, is another contender for smallest known insect in the world. * Beetles of the tribe Nanosellini are all less than {{cvt|1|mm}} long; the smallest confirmed specimen is of ''Scydosella musawasensis'' at {{cvt|325|μm|mm}} long; a few other nanosellines are reportedly smaller, in historical literature, but none of these records have been confirmed using accurate modern tools. These are among the tiniest non-parasitic insects.<ref>{{cite journal | doi = 10.3897/zookeys.526.6531 | author = Polilov, A.A. | year = 2015 | title = How small is the smallest? New record and remeasuring of ''Scydosella musawasensis'' Hall, 1999 (Coleoptera, Ptiliidae), the smallest known free-living insect. | journal = ZooKeys | issue = 526 | pages = 61–64 | pmid=26487824 | pmc=4607844 | doi-access = free | bibcode = 2015ZooK..526...61P }}</ref> [[File:Grand Cayman pygmy blue (Brephidium exilis thompsoni) 2.JPG|thumb|Western pygmy blue (''Brephidium exilis thompsoni'')]] * The western pygmy blue (''Brephidium exilis'') is one of the smallest butterflies in the world, with a wingspan of about {{cvt|1|cm|abbr=on}}.<ref>{{Cite web |url=https://animals.mom.me/western-pygmy-blue-butterfly-6104.html |title = Facts on the Western Pygmy Blue Butterfly}}</ref>
=== Echinoderms (Echinodermata) === The smallest sea cucumber, and also the smallest echinoderm, is ''Psammothuria ganapati'', a synaptid that lives between sand grains on the coast of India. Its maximum length is {{cvt|4|mm}}.<ref name = Rao1968>{{cite journal | last = Rao | first = G. Chandrasekhara | year = 1968 | title = On ''Psammothuria ganapatii'' n. gen. n. sp., an interstitial holothurian from the beach sands of waltair coast and its autecology | journal = Proceedings of the Indian Academy of Sciences, Section B | volume = 67 | issue = 5 | pages = 201–206 | doi = 10.1007/BF03053902 | s2cid = 135202924 |url=https://link.springer.com/article/10.1007/BF03053902 | url-access = subscription }}</ref><ref name = Gilpin2006>{{Cite book | last = Gilpin | first = Daniel | year = 2006 | title = Starfish, urchins, and other echinoderms | publisher = David West Children's Books | place = London | isbn = 0-7565-1611-0 | page = [https://archive.org/details/starfishurchinso0000gilp/page/41 41] |url=https://archive.org/details/starfishurchinso0000gilp/page/41 }}</ref>
==== Sea urchins ==== The smallest sea urchin, ''Echinocyamus scaber'', has a test {{cvt|6|mm}} across.<ref name = Gilpin2006 />
==== Starfish ==== ''Patiriella parvivipara'' is the smallest starfish, at {{cvt|5|mm}} across.<ref name = Gilpin2006 />
=== Fish === {{main|List of smallest fish}} [[File:Paedocypris progenetica 001.jpg|thumb|''Paedocypris progenetica'', the smallest known fish]] * One of the smallest vertebrates and one of the smallest fish is ''Paedocypris progenetica'' from Indonesia, with mature females measuring as little as {{convert|7.9|mm|abbr=on}} in standard length.<ref name=Pprogenetica>{{FishBase| genus = Paedocypris | species = progenetica | month = September| year = 2017}}</ref> This fish, a member of the carp family, has a translucent body and a head unprotected by a skeleton. * One of the smallest fish based on the minimum size at maturity is ''Schindleria brevipinguis'' from Australia, their females reach {{convert|7|mm|in|abbr=on}} and males {{convert|6.5|mm|in|abbr=on}}.<ref>{{Cite web|title=Fishes|url=https://australian.museum/learn/animals/fishes/|access-date=February 14, 2019|archive-url=https://web.archive.org/web/20221003182122/https://australian.museum/learn/animals/fishes/|archive-date=October 3, 2022|date=June 2020|website=The Australian Museum}}</ref> Males of ''S. brevipinguis'' have an average standard length of {{convert|7.7|mm|abbr=on}}; a gravid female was {{convert|8.4|mm|abbr=on}}.<ref name=fishbase>{{FishBase|genus=Schindleria|species=brevipinguis|year=2017|month=September}}</ref> This fish, a member of the goby family, differs from similar members of the group in having its first anal fin ray further forward, under dorsal fin 4. * Male individuals of the anglerfish species ''Photocorynus spiniceps'' have been documented to be {{convert|6.2|-|7.3|mm|in|abbr=on}} at maturity, and thus claimed to be a smaller species. However, these survive only by sexual parasitism and the female individuals reach the significantly larger size of {{convert|50.5|mm|in|abbr=on}}.<ref>{{cite news|url=https://news.bbc.co.uk/1/hi/sci/tech/4645708.stm| work=BBC News | title=Scientists find 'smallest fish' | date=2006-01-25 | access-date=2010-05-23}}</ref><ref>{{cite web|url=http://www.amonline.net.au/fishes/faq/smallest.htm |title=What is the smallest species of fish? |publisher=Amonline.net.au |date=2013-09-27 |access-date=2013-10-03 |archive-url=https://web.archive.org/web/20090220152323/http://amonline.net.au/fishes/faq/smallest.htm |archive-date=February 20, 2009}}</ref><ref>{{cite news|url=https://news.bbc.co.uk/2/hi/science/nature/4666736.stm | work=BBC News | title=Smallest fish compete for honours | date=2006-01-31 | access-date=2010-05-23}}</ref><ref>{{cite web|url=http://www.livescience.com/animalworld/041027_Smallest_Fish.html|archive-url=https://web.archive.org/web/20080706153957/http://www.livescience.com/animalworld/041027_Smallest_Fish.html|title=Bragging Rights: The Smallest Fish Ever | LiveScience|website=Live Science |archive-date=July 6, 2008}}</ref>
=== Amphibians (Amphibia) ===
==== Frogs and toads (Anura) ==== [[File:Brachycephalus dacnis (ZUEC-AMP 25275; on fingertip).png|thumb|left|A paratype specimen of ''Brachycephalus dacnis'' specimen on a human fingertip]] thumb|460px|A relative comparison of some of the smallest frogs The smallest vertebrate (and smallest amphibian) known is ''Brachycephalus pulex'', a Brazilian flea toad, with a minimum adult snout–vent length of {{convert|6.45|mm|in}}.<ref name="smallest_vertebrate">{{Cite journal |last1=Bolaños |first1=Wendy H. |last2=Dias |first2=Iuri Ribeiro |last3=Solé |first3=Mirco |date=2024-02-07 |title=Zooming in on amphibians: Which is the smallest vertebrate in the world? |url=https://onlinelibrary.wiley.com/doi/10.1111/zsc.12654 |journal=Zoologica Scripta |volume=53 |language=en |issue=4 |pages=414–418 |doi=10.1111/zsc.12654 |s2cid=267599475 |issn=0300-3256 |eissn=1463-6409|url-access=subscription }}</ref> ''Brachycephalus dacnis'' is similarly tiny, with a minimum adult length of {{convert|6.95|mm|in}}.<ref>{{Cite journal |last1=Toledo |first1=Luís Felipe |last2=Botelho |first2=Lucas Machado |last3=Carrasco-Medina |first3=Andres Santiago |last4=Gray |first4=Jaimi A. |last5=Ernetti |first5=Julia R. |last6=Gama |first6=Joana Moura |last7=Lyra |first7=Mariana Lucio |last8=Blackburn |first8=David C. |last9=Nunes |first9=Ivan |last10=Muscat |first10=Edelcio |date=2024-10-25 |title=Among the world's smallest vertebrates: a new miniaturized flea-toad (Brachycephalidae) from the Atlantic rainforest |journal=PeerJ |language=en |volume=12 |article-number=e18265 |doi=10.7717/peerj.18265 |doi-access=free |pmid=39469590 |issn=2167-8359|pmc=11514764 }}</ref> Other very small frogs include: * ''Paedophryne amauensis'' from Papua New Guinea, ranging in length from {{convert|7.0|-|8.0|mm|in|abbr=on}}, and {{convert|7.7|mm|in|abbr=on}} on average.<ref name="TinyAustralian">{{cite news|title=World's tiniest frogs found in Papua New Guinea |url=https://www.theaustralian.com.au/news/breaking-news/worlds-tiniest-frogs-found-in-papua-new-guinea/story-fn3dxity-1226242332383 |newspaper=The Australian |date=12 January 2012 |access-date=11 January 2012}}</ref><ref name="Rittmeyeretal">{{cite journal |last1=Rittmeyer |first1=Eric N. |last2=Allison |first2=Allen |last3=Gründler |first3=Michael C. |last4=Thompson |first4=Derrick K. |last5=Austin |first5=Christopher C. |year=2012 |title=Ecological guild evolution and the discovery of the world's smallest vertebrate |journal=PLOS ONE |volume=7 |issue=1 |article-number= e29797|doi=10.1371/journal.pone.0029797 |pmid=22253785 |pmc=3256195|bibcode=2012PLoSO...729797R |doi-access=free}}</ref> * ''Brachycephalus didactylus'' from Brazil (reported as {{cvt|9.6|–|9.8|mm}}) * several species of ''Eleutherodactylus'' such as ''E. iberia'' (around {{cvt|10|mm}}), ''E. limbatus'' ({{cvt|8.5|–|12|mm}}), and ''Eleutherodactylus orientalis'' ({{cvt|12.5|mm}}) from Cuba, * Gardiner's Frog ''Sechellophryne gardineri'' from the Seychelles (up to {{cvt|11|mm}}), * several species of ''Stumpffia'' such as ''S. tridactyla'' ({{cvt|8.6|–|12|mm}}) and ''S. pygmaea'' (males {{cvt|10|–|12.5|mm}}; females: {{cvt|11|mm}}) * ''Wakea madinika'' (males: {{cvt|11|–|13|mm}}; females: {{cvt|15|–|16|mm}}) from Madagascar.
The two species ''Microhyla borneensis'' (males: {{cvt|10.6|–|13|mm}}; females: {{cvt|16|–|19|mm}})<ref>{{cite web|url=https://www.sciencedaily.com/releases/2010/08/100825094915.htm|title=Tiny, new, pea-sized frog is old world's smallest|website=ScienceDaily}}</ref><ref>{{cite web|url=https://www.ecologyasia.com/verts/amphibians/bornean-chorus-frog.htm|title=Bornean Chorus Frog - Microhyla borneensis (Microhyla nepenthicola)|website=ecologyasia.com}}</ref> and ''Arthroleptella rugosa'' (males: {{cvt|11.9|–|14.1|mm}}; females: {{cvt|15.5|mm}}) were once the smallest known frogs from the Old World. In general these extremely small frogs occur in tropical forest and montane environments. There is relatively little data on size variation among individuals, growth from metamorphosis to adulthood or size variation among populations in these species. Additional studies and the discovery of further minute frog species are likely to change the rank order of this list.
==== Salamanders, newts and allies (Urodela) ==== The average snout-to-vent length (SVL) of several specimens of the salamander ''Thorius arboreus'' was {{convert|17|mm|in|abbr=on}}.<ref>{{cite journal | last1=Rittmeyer | first1=Eric N. | last2=Allison | first2=Allen | last3=Gründler | first3=Michael C. | last4=Thompson | first4=Derrick K. | last5=Austin | first5=Christopher C. | title=Ecological Guild Evolution and the Discovery of the World's Smallest Vertebrate | journal=PLOS ONE | publisher=Public Library of Science (PLoS) | volume=7 | issue=1 | date=2012-01-11 | issn=1932-6203 | doi=10.1371/journal.pone.0029797 | doi-access=free | article-number=e29797| pmid=22253785 | pmc=3256195 | bibcode=2012PLoSO...729797R }}</ref>
=== Sauropsids (Sauropsida) ===
==== Lizards and snakes (Squamata) ==== [[File:Juvenile Brookesia micra on finger tip.png|thumb|A juvenile ''Brookesia micra'', a species of chameleon, on a finger tip]] * The miniature chameleon ''Brookesia nana'', with a snout-vent length of {{cvt|13.5|mm}}, may represent the smallest known lizard and smallest reptile.<ref>{{Cite journal|last1=Glaw|first1=Frank|last2=Köhler|first2=Jörn|last3=Hawlitschek|first3=Oliver|last4=Ratsoavina|first4=Fanomezana M.|last5=Rakotoarison|first5=Andolalao|last6=Scherz|first6=Mark D.|last7=Vences|first7=Miguel|date=2021-01-28|title=Extreme miniaturization of a new amniote vertebrate and insights into the evolution of genital size in chameleons|journal=Scientific Reports|language=en|volume=11|issue=1|page=2522|doi=10.1038/s41598-020-80955-1|pmid=33510189|pmc=7844282|issn=2045-2322}}</ref><ref>{{Cite web|title=World's Smallest Chameleon Discovered And It's 'Surprisingly' Well-Endowed|url=https://www.iflscience.com/plants-and-animals/worlds-smallest-chameleon-discovered-and-its-surprisingly-wellendowed/|access-date=2021-01-28|website=IFLScience|date=28 January 2021 |language=en}}</ref> * The dwarf gecko (''Sphaerodactylus ariasae'') is also one of the smallest known reptile species, with a snout-vent length of {{convert|16|mm|in}}.<ref>Pennsylvania State University (2001). ''[http://science.psu.edu/news-and-events/2001-news/Hedges11-2001.htm World's Smallest Lizard Discovered in the Caribbean]''. Retrieved 26 January 2009.</ref> ''S. ariasae'' was first described in 2001 by the biologists Blair Hedges and Richard Thomas. This dwarf gecko lives in Jaragua National Park in the Dominican Republic and on Beata Island (''Isla Beata''), off the southern coast of the Dominican Republic.<ref>{{cite news|url=https://news.bbc.co.uk/2/hi/science/nature/1689313.stm | work=BBC News | title=Tiny gecko is 'world's smallest' | date=2001-12-03 | access-date=2010-05-23}}</ref><ref>{{cite web |url=http://forests.org/archive/samerica/wosmliza.htm |title=12/03/01 -- World's Smallest Reptile Discovered in Caribbean |access-date=2011-12-14 |archive-url=https://web.archive.org/web/20021104122941/http://forests.org/archive/samerica/wosmliza.htm |archive-date=2002-11-04 }}</ref> A few ''Brookesia'' chameleons from Madagascar are equally small, with a reported snout-vent length of {{cvt|15|–|18|mm}} for male dwarf chameleons (''B. minima''), {{cvt|14|–|19|mm}} for male Mount d'Ambre leaf chameleons (''B. tuberculata'')<ref>Glaw, F., & Vences, M. (2007). ''A Field Guide to the Amphibians and Reptiles of Madagascar, 3d edition.'' Frosch Verlag. {{ISBN|978-3-929449-03-7}}</ref> and {{cvt|15|–|16|mm}} for male ''B. micra'',<ref>{{Cite journal| last1 = Glaw | first1 = F. | last2 = Köhler | first2 = J. R. | last3 = Townsend | first3 = T. M. | last4 = Vences | first4 = M. | editor1-last = Salamin | editor1-first = Nicolas | title = Rivaling the World's Smallest Reptiles: Discovery of Miniaturized and Microendemic New Species of Leaf Chameleons (Brookesia) from Northern Madagascar | doi = 10.1371/journal.pone.0031314 | journal = PLOS ONE | volume = 7 | issue = 2 | article-number = e31314 | year = 2012 | pmid = 22348069| pmc =3279364 | bibcode = 2012PLoSO...731314G | doi-access = free}}</ref> though females are larger.
[[File:Leptotyphlops carlae.jpg|thumb|left|Barbados threadsnake]] * One of the smallest known snakes is the Barbados threadsnake (''Leptotyphlops carlae''). Adults average about {{convert|10|cm|in|0|abbr=on}} long, which is only about twice as long as the hatchlings. The common blind snake (''Indotyphlops braminus'') measures {{convert|5.1–10.2|cm|in|0|abbr=on}} long, occasionally up to {{convert|15|cm|in|0|abbr=on}} long.<ref name="FMNH">{{cite web|url=https://www.floridamuseum.ufl.edu/herpetology/fl-snakes/list/indotyphlops-braminus/|title=Indotyphlops braminus :: Florida Museum of Natural History|website=floridamuseum.ufl.edu|date=17 August 2020}}</ref><ref>{{cite web|url=http://www.reptilesmagazine.com/Blind-Snakes/|title=Blind Snakes|website=reptilesmagazine.com|date=December 2011}}</ref>
==== Turtles and tortoises (Testudines) ==== The smallest turtle is the speckled padloper tortoise (''Homopus signatus'') from South Africa. The males measure {{convert|6|-|8|cm|in|abbr=on}}, while females measure up to almost {{convert|10|cm|in|abbr=on}}.<ref>Branch, B. (1998). ''Field Guide to Snakes and other Reptiles of Southern Africa.'' 3d edition. Struik Publishers. {{ISBN|1-86872-040-3}}</ref>
=== Archosaurs (Archosauria){{refn|group=note|Archosaurs are a clade within Sauropsida, but are significantly different from all other reptiles.}}===
==== Crocodiles and close relatives (Crocodylomorpha) ==== * The smallest extant crocodilian is the Cuvier's dwarf caiman (''Paleosuchus palpebrosus'') from northern and central South America. It reaches up to {{convert|1.6|m|ft|abbr=on}} in length.<ref>{{cite web|url=http://www.flmnh.ufl.edu/cnhc/csp_ppal.htm|archive-url=https://web.archive.org/web/20071013044335/http://www.flmnh.ufl.edu/cnhc/csp_ppal.htm|archive-date=13 October 2007|title=Paleosuchus palpebrosus (Cuvier, 1807)}}</ref>
==== Pterosaurs (Pterosauria) ==== {{further|Pterosaur size}} ''Nemicolopterus'' was one of the smallest pterosaurs, it reached about {{cvt|25|cm}} in wingspan.<ref name=wangetal2008>{{cite journal |last1= Wang |first1= X. |last2= Kellner |first2= A.W.A. |last3= Zhou |first3= Z. |last4= Campos |first4= D.A. |year= 2008 |title= Discovery of a rare arboreal forest-dwelling flying reptile (Pterosauria, Pterodactyloidea) from China |journal= Proceedings of the National Academy of Sciences |volume= 105|issue= 6 |pages= 1983–1987 |doi= 10.1073/pnas.0707728105 |pmid=18268340 |pmc=2538868|bibcode= 2008PNAS..105.1983W|doi-access= free }}</ref>
==== Non-avian dinosaurs (Dinosauria) ==== {{further|Dinosaur size}} Sizes of non-avian dinosaurs are commonly labelled with a level of uncertainty, as the available material often (or even usually) is incomplete. The smallest known extinct non-avian dinosaur is ''Anchiornis'', a genus of feathered dinosaur that lived in what is now China during the Late Jurassic Period 160 to 155 million years ago. Adult specimens range from {{convert|34|cm|in|abbr=on}} long, and the weight has been estimated at up to {{convert|110|g|oz|abbr=on}}.<ref>Xu, X., Zhao, Q., Norell, M., Sullivan, C., Hone, D., Erickson, G., Wang, X., Han, F. and Guo, Y. (2009). "A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin." Chinese Science Bulletin, 6 pages, accepted November 15, 2008.</ref> ''Parvicursor'' was initially seen as one of the smallest non-avian dinosaurs known from an adult specimen, at {{cvt|39|cm|in}} in length, and {{cvt|162|g}} in weight.<ref>[http://www.technosaurs.ca/tag/default.aspx?id=114 Which was the smallest dinosaur?] {{webarchive|url=https://web.archive.org/web/20110706204350/http://www.technosaurs.ca/tag/default.aspx?id=114 |date=2011-07-06 }} Royal Tyrrell Museum. Last accessed 2008-05-23.</ref> However, in 2022 its holotype was concluded to represent a juvenile individual.<ref>{{cite journal| vauthors = Averianov AO, Lopatin AV |title=A re-appraisal of ''Parvicursor remotus'' from the Late Cretaceous of Mongolia: implications for the phylogeny and taxonomy of alvarezsaurid theropod dinosaurs |journal=Journal of Systematic Palaeontology |year=2022 |volume=19 |issue=16 |pages=1097–1128 |doi=10.1080/14772019.2021.2013965 |s2cid=247222017 }}</ref> ''Epidexipteryx'' reached {{cvt|25|-|30|cm}} in length and {{cvt|164|-|220|g}} in weight.<ref>{{cite journal | last1 = Zhang | first1 = F. | last2 = Zhou | first2 = Z. | last3 = Xu | first3 = X. | last4 = Wang | first4 = X. | last5 = Sullivan | first5 = C. | year = 2008 | title = "A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers", Supplementary Information | journal = Nature | volume = 455| issue = 7216 | pages = 1105–8| doi = 10.1038/nature07447 | pmid = 18948955 | bibcode = 2008Natur.455.1105Z | s2cid = 4362560 }}</ref><ref>{{Cite book|last=Paul|first=Gregory S.|title=The Princeton Field Guide to Dinosaurs|year=2016|publisher=Princeton University Press|isbn=978-1-78684-190-2|oclc=985402380|page=139}}</ref>
==== Birds (Aves) ==== [[File:Mellisuga helenae Size Comparison.svg|thumb|Size of a bee hummingbird, the smallest known bird and dinosaur, compared to a human hand]] * With a mass of approximately {{convert|1.95|g|oz}} and a length of {{convert|5.5|cm|in|abbr=off}}, the bee hummingbird (''Mellisuga helenae'') is the smallest known dinosaur as well as the smallest bird species, and the smallest warm-blooded vertebrate. Called the ''zunzuncito'' in its native habitat on Cuba, it is lighter than a Canadian or U.S. penny. It is said that it is "more apt to be mistaken for a bee than a bird".<ref>{{cite web|url=http://www.mschloe.com/hummer/carib.htm|archive-url=https://archive.today/20130703194008/http://www.mschloe.com/hummer/carib.htm|title=Hummingbirds of the Caribbean|archive-date=July 3, 2013|website=mschloe.com|url-status=usurped}}</ref> The bee hummingbird eats half its total body mass and drinks eight times its total body mass each day. Its nest is {{cvt|3|cm}} across. * The smallest waterfowl is the pygmy goose (''Nettapus''). African species reaches the average weight of about {{convert|285|g}} for males and {{convert|260|g}} for females and length of single wing between {{convert|142| mm}} and {{convert|165|mm}}.<ref>{{cite book | title=Ducks, Geese and Swans: Species accounts (Cairina to Mergus) [Volume 2 of Ducks, Geese and Swans: Species accounts]|first1=Janet|last1=Kear|publisher= Oxford University Press |location=Oxford |year=2005 |page=908 |isbn=978-0-19-861009-0|url=https://books.google.com/books?id=D2K-9k-_EFcC&q=Nettapus}}</ref> The second smallest waterfowl is the extinct ''Mioquerquedula'' from the Miocene.<ref>{{Cite web |url= https://www.researchgate.net/publication/250002885 |title= Dabbling Ducks (Aves: Anatidae) from the Middle Miocene of Mongolia |date= October 2018 |website= ResearchGate}}</ref> * The smallest penguin species is the little blue penguin (''Eudyptula minor''), which stands around {{convert|30|-|33|cm|in|abbr=on}} tall and weighs {{convert|1.2|-|1.3|kg|lb|abbr=on}}.<ref name="pengsent">{{cite web|url=http://mesh.biology.washington.edu/penguinProject/Little|title=Little Penguin – Penguin Project|last=Grabski|first=Valerie|year=2009|publisher=Penguin Sentinels/University of Washington|archive-url=https://web.archive.org/web/20111216162812/http://mesh.biology.washington.edu/penguinProject/Little|archive-date=16 December 2011|access-date=24 September 2022}}</ref> * The smallest bird of prey is the black-thighed falconet (''Microhierax fringillarius''), with a wingspan of {{convert |27|-|32|cm|in}}, roughly the size of a sparrow.<ref name="raptors book">Raptors of the World by Ferguson-Lees, Christie, Franklin, Mead & Burton. Houghton Mifflin (2001)828-829, {{ISBN|0-618-12762-3}}</ref>
=== Non-mammalian synapsids (Synapsida) === The smallest Mesozoic mammaliaform was ''Hadrocodium'' with a skull of {{cvt|1.5|cm}} in length and a body mass of {{cvt|2|g}}.<ref>{{cite book | isbn = 978-0-19-850761-1 | url = https://books.google.com/books?id=GswTDAAAQBAJ&dq=Gobiconodon+kg&pg=PA183 | title = The Origin and Evolution of Mammals | publisher = Oxford University Press, USA | date = 2005 | access-date = 22 September 2022 | page = 183 | author = T. S. Kemp }}</ref>
=== Mammals (Mammalia) ===
==== Marsupials (Marsupialia) ==== [[File:Long-tailed planigale.jpg|thumb|Long-tailed planigale]] The smallest marsupial is the long-tailed planigale from Australia. It has a body length of {{convert|110-130|mm|in}} (including tail) and weighs {{convert|4.3|g|oz}} on average. The Pilbara ningaui is considered to be of similar size and weight.<ref name="SmallestAnimals" />
==== Shrews (Eulipotyphla) ==== [[File:Suncus etruscus.jpg|thumb|Etruscan shrew]] The Etruscan shrew (''Suncus etruscus''), is the smallest mammal by mass, weighing about {{convert|1.8|g|oz|abbr=on}} on average.<ref>{{cite journal|last1=Jürgens |first1=Klaus D. |date=August 2002 |title=Etruscan shrew muscle: the consequences of being small |url=https://jeb.biologists.org/content/205/15/2161 |journal=Journal of Experimental Biology |volume=205 |issue=15 |pages=2161–2166 |doi=10.1242/jeb.205.15.2161 |pmid=12110649 |bibcode=2002JExpB.205.2161J |access-date=April 27, 2020|url-access=subscription }}</ref> The shrew-like ''Batodonoides vanhouteni'', weighed {{convert|1.3|g|oz}} is considered as one of the smallest mammal ever lived in description, although known specimen is juvenile.<ref>{{cite journal |last1=Bloch |first1=Jonathan I. |last2=Rose |first2=Kenneth D. |last3=Gingerich |first3=Philip D. |year=1998 |title=New Species of ''Batodonoides'' (Lipotyphla, Geolabididae) from the Early Eocene of Wyoming: Smallest Known Mammal? |journal=Journal of Mammalogy |volume=79 |issue=3 |pages=804–827 |jstor=1383090 |doi=10.2307/1383090 |doi-access = free}}</ref>
==== Bats (Chiroptera) ==== The Kitti's hog-nosed bat (''Craseonycteris thonglongyai''), also known as the bumblebee bat, from Thailand and Myanmar<ref>{{Cite iucn | author = Bates, P. | author2 = Bumrungsri, S. | author3 = Francis, C. | name-list-style = amp | title = Craseonycteris thonglongyai | volume = 2008 | article-number = e.T5481A11205556 |year = 2008 | doi = 10.2305/IUCN.UK.2008.RLTS.T5481A11205556.en }} Listed as Vulnerable</ref> is the smallest mammal, at {{convert|29|-|33|mm|in}} in length and {{convert|2|g|oz}} in weight.<ref>Donati, Annabelle, and Pamela Johnson. "Which mammal is the smallest?." I wonder which snake is the longest: and other neat facts about animal records. Racine, Wis.: Western Pub. Co., 1993. 8. Print.</ref><ref name=Edge>{{Cite web | url = http://www.edgeofexistence.org/mammals/species_info.php?id=49 | title = Bumblebee bat (''Craseonycteris thonglongyai'') | work = EDGE Species | access-date = 2008-04-10 | archive-url = https://web.archive.org/web/20100921174949/http://www.edgeofexistence.org/mammals/species_info.php?id=49 | archive-date = 21 September 2010}}</ref>
==== Carnivorans (Carnivora) ==== The smallest member of the order Carnivora is the least weasel (''Mustela nivalis''), with an average body length of {{convert|114|–|260|mm|in|abbr=on}}. It weighs {{cvt|29.5|–|250|g}} with females being lighter.<ref>{{Harvnb|Heptner|Sludskii|2002|p=991}}</ref>
==== Rodents (Rodentia) ==== The smallest known member of the rodent order is the Baluchistan pygmy jerboa, with an average body length of {{convert|3.8|cm|in|abbr=on}}.<ref name=SmallestAnimals>{{cite web|url=http://www.thetoptenz.net/smallest-animals/|title=World's Smallest Animals |publisher=Thetoptenz.net |date=2013-09-29 |access-date=2013-10-03}}</ref>
==== Primates (Primates) ==== [[File:Madame Berthe's Mouse Lemur.jpg|thumb|Madame Berthe's mouse lemur]] The smallest primate is Madame Berthe's mouse lemur (''Microcebus berthae''), found in Madagascar,<ref>[http://www.primates.co.uk/lemurs/pygmy-mouselemur.html (Retrieved on March 17, 2010).] {{webarchive |url=https://web.archive.org/web/20090716201423/http://www.primates.co.uk/lemurs/pygmy-mouselemur.html |date=July 16, 2009 }}</ref> with an average body length of {{convert|9.2|cm|in|abbr=on}}.
==== Cetaceans (Cetacea) ==== The smallest cetacean, which is also (as of 2006) the most endangered, is the vaquita, a species of porpoise. Male vaquitas grow to an average of around {{convert|135|cm|in|abbr=on}}; the females are slightly longer, averaging about {{convert|141|cm|in|abbr=on}} in length.<ref>{{Harvnb|Brownell|Findley|Vidal|Robles|1987|pp=23–24}}</ref>
== Embryophytes (Embryophyta) == === Gymnosperms (Gymnospermae) === ''Zamia pygmaea'' is a cycad found in Cuba, and the smallest known gymnosperm.<ref>{{cite book |last1=Bhatnagar |first1=S. P. |last2=Moitra |first2=Alok |title=Gymnosperms |date=1996 |publisher=New Age International |isbn=978-81-224-0792-1 |url=https://books.google.com/books?id=4dvyNckni8wC |access-date=16 April 2022 |language=en}}</ref> It grows to a height of {{cvt|25|cm|0}}.<ref>{{Cite book|author1=P.S.Dhami|title=A textbook of Biology|author2=G.Chopra|author3=H.N.Srivastava|publisher=Pradeep Publication|year=2015|location=Jalandhar, Punjab}}</ref>
=== Angiosperms (Angiospermae) === [[File:WolffiaArrhiza2.jpg|thumb|''Wolffia arrhiza'' on human fingers. Every speck of less than {{cvt|1|mm}} length is an individual plant.]] Duckweeds of the genus ''Wolffia'' are the smallest angiosperms.<ref>{{cite web|url=https://www.loc.gov/rr/scitech/mysteries/smallestflower.html |title=What is the smallest flower in the world? |publisher=Loc.gov |access-date=2013-10-03}}</ref> Fully grown, they measure {{cvt|300|by|600|μm|mm}} and reach a mass of just 150 μg.
==== Dicotyledons ==== The smallest known dicotyledon plant is the Himalayan dwarf mistletoe (''Arceuthobium minutissimum''). Shoots grow up to {{cvt|5|mm}} in height.<ref>{{cite journal |last1=Datta |first1=R. M. |title=Occurrence of a Hermaphrodite Flower in Arceuthobium minutissimum Hook. f., the Smallest Known Dicotyledonous Plant |journal=Nature |date=February 1951 |volume=167 |issue=4240 |pages=203–204 |doi=10.1038/167203a0 |pmid=14806428 |bibcode=1951Natur.167..203D |s2cid=4181798 |url=https://www.nature.com/articles/167203a0 |access-date=16 April 2022 |language=en |issn=1476-4687|url-access=subscription }}</ref>
== Other ==
=== Nanobes === Nanobes are thought by some scientists to be the smallest known organisms,<ref name=Nanjundiah2000>{{Cite journal | last = Nanjundiah | first = V. | year = 2000 | title = The smallest form of life yet? | journal = Journal of Biosciences | volume = 25 | issue = 1 | pages = 9–10 |url=http://eprints.iisc.ernet.in/archive/00001799/01/25smallest25(1)-9to10mar2000.pdf | doi = 10.1007/BF02985175 | pmid = 10824192 | s2cid = 29030837 }}</ref> about one tenth the size of the smallest known bacteria. Nanobes, tiny filamental structures first found in some rocks and sediments, were first described in 1996 by Philippa Uwins of the University of Queensland, but it is unclear what they are, and if they are alive.<ref name=nanobepaper1998>{{cite journal |author1=Uwins, Philippa J.R. |display-authors=etal |year=1998 |title=Novel nano-organisms from Australian sandstones |journal=American Mineralogist | volume=83 |issue=11–12 |pages=1541–1550, Part 2 |doi=10.2138/am-1998-11-1242 |bibcode=1998AmMin..83.1541U |url=http://www.microscopy-uk.org.uk/nanobes/nanobes.pdf }}</ref>
== See also == * Largest organisms * Largest prehistoric organisms * Candidatus Sukunaarchaeum mirabile
== Notes == {{reflist|group=note}}
== References == {{Reflist|colwidth=30em}}
== Other references == * {{Cite book|last1=Heptner|first1=V. G.|last2=Sludskii|first2=A. A.|url=https://archive.org/details/mammalsofsov212001gept|title=Mammals of the Soviet Union. Vol. II, part 1b, Carnivores (Mustelidae and Procyonidae)|publisher=Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation|year=2002|isbn=90-04-08876-8}} * {{Cite journal |last1=Brownell |first1=Robert L. |last2=Findley |first2=Lloyd T. |last3=Vidal |first3=Omar |last4=Robles |first4=Alejandro |last5=Manzanilla |first5= N. Silvia |year=1987 |title=External Morphology and Pigmentation of the Vaquita, Phocoena Sinus (cetacea: Mammalia) |journal=Marine Mammal Science |display-authors= 4 |volume=3 |issue=1 |pages=22–30 |doi=10.1111/j.1748-7692.1987.tb00149.x |bibcode=1987MMamS...3...22B |issn=1748-7692}}
== External links == * [http://entomology.ifas.ufl.edu/creatures/misc/beetles/featherwing_beetles.htm Featherwing beetles] on the UF / IFAS Featured Creatures Web site {{Records}}
* Category:Lists of organisms