The smallest organisms found on Earth can be determined according to various aspects of

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...

size, including

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). ...

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different ele ...

height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For example, "The height of that building is 50 m" or "The height of an airplane in-flight is ab ...

length Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Inte ...

, or

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...

size. Given the incomplete nature of scientific knowledge, it is possible that the smallest organism is undiscovered. Furthermore, there is some debate over the definition of

life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy ...

, and what entities qualify as organisms; consequently the smallest known organism (microorganism) is debatable.

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. The genome of ''

Nanoarchaeum equitans ''Nanoarchaeum equitans'' is a species of marine archaea that was discovered in 2002 in a hydrothermal vent off the coast of Iceland on the Kolbeinsey Ridge by Karl Stetter. It has been proposed as the first species in a new phylum. Strains of ...

'' is 490,885 nucleotides long.

''Pelagibacter ubique''

'' Pelagibacter ubique'' is one of the smallest known free-living bacteria, with a length of and an average cell diameter of . 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.

''Mycoplasma genitalium''

Mycoplasma genitalium ''Mycoplasma genitalium'' (''MG'', commonly known as Mgen) is a sexually transmitted, small and pathogenic bacterium that lives on the mucous epithelial cells of the urinary and genital tracts in humans. Medical reports published in 2007 and 2 ...

'', a

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

which lives in the

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...

bladder, waste disposal organs, genital, and respiratory tracts, is thought to be the smallest known organism capable of independent

growth Growth may refer to: Biology * Auxology, the study of all aspects of human physical growth * Bacterial growth * Cell growth * Growth hormone, a peptide hormone that stimulates growth * Human development (biology) * Plant growth * Secondary grow ...

and

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...

. With a size of approximately 200 to 300 nm, ''M. genitalium'' is an ultramicrobacterium, smaller than other small bacteria, including

rickettsia ''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "ricke ...

and

chlamydia Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium '' Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear they may occur only several we ...

. 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

ultrafilter In the mathematical field of order theory, an ultrafilter on a given partially ordered set (or "poset") P is a certain subset of P, namely a maximal filter on P; that is, a proper filter on P that cannot be enlarged to a bigger proper filter o ...

. A complicating factor is nutrient-downsized bacteria, bacteria that become much smaller due to a lack of available

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...

''Nanoarchaeum''

'' is a species of

microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

in diameter. It was discovered in 2002 in a

hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspo ...

off the coast of

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

Karl Stetter Karl Otto Stetter (born 16 July 1941) is a German microbiologist and authority on astrobiology. He is an expert on microbial life at high temperatures. Career Stetter was born in Munich and studied biology at the Technical University of Munich. ...

. A

thermophile A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...

that grows in near-boiling temperatures, ''Nanoarchaeum'' appears to be an obligatory symbiont on the

archaeon Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebact ...

Ignicoccus ''Ignicoccus'' is a genus of hyperthermophillic Archaea living in marine hydrothermal vents. They were discovered in samples taken at the Kolbeinsey Ridge north of Iceland, as well as at the East Pacific Rise (at 9 degrees N, 104 degrees W) i ...

''; it must be in contact with the host organism to survive.

Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

recognizes ''Nanoarchaeum equitans'' as the smallest living organism.

Eukaryotes (Eukaryota)

Prasinophyte The prasinophytes are a group of unicellular green algae. Prasinophytes mainly include marine planktonic species, as well as some freshwater representatives.Sym, S. D. and Pienaar, R. N. 1993. The class Prasinophyceae. In Round, F. E. and Chapm ...

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

e of the genus '' Ostreococcus'' are the smallest free-living

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacter ...

. The single cell of an ''Ostreococcus'' measures across.

Viruses

Some

biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual cell, a multicellular organism, or a community of interacting populations. They usually specialize ...

s consider

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

es to be non-living because they lack a cellular structure and cannot metabolize 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 In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...

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. The smallest viruses in terms of genome size are single-stranded DNA ( ssDNA) viruses. Perhaps the most famous is the

bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bac ...

Phi-X174 with a genome size of 5,386

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecu ...

s. However, some ssDNA viruses can be even smaller. For example, Porcine circovirus type 1 has a genome of 1,759 nucleotides and a

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...

diameter of . As a whole, the viral family geminiviridae is about in length. However, the two capsids making up the virus are fused; divided, the capsids would be 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. The smallest

RNA virus An RNA virus is a virusother than a retrovirusthat has ribonucleic acid ( RNA) as its genetic material. The nucleic acid is usually single-stranded RNA (ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA virus ...

in terms of

size is phage BZ13 strain T72 at 3,393 nucleotides length. Viruses using both DNA and RNA in their replication (

retrovirus A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptas ...

es) range in size from 7,040 to 12,195 nucleotides. The smallest double-stranded

DNA virus A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and ...

es are the hepadnaviruses such as

hepatitis B Hepatitis B is an infectious disease caused by the '' Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. ...

, at 3.2 kb and ; parvoviruses have smaller capsids, at , but larger genomes, at 5 kb. It is important to consider other self-replicating genetic elements, such as satelliviruses,

viroid Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants), and most cause diseases, whose respective economi ...

s and ribozymes.

Animals (Animalia)

Several species of

Myxozoa Myxozoa (etymology: Greek: μύξα ''myxa'' "slime" or "mucus" + thematic vowel o + ζῷον ''zoon'' "animal") is a subphylum of aquatic cnidarian animals – all obligate parasites. It contains the smallest animals ever known to have lived. O ...

(obligately parasitic

cnidarian Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that th ...

s) never grow larger than . One of the smallest species (''Myxobolus shekel'') is no more than when fully grown, making it the smallest known animal.

Molluscs (Molluska)

Bivalvia

The shell of the nut clam ''

Condylonucula maya ''Condylonucula maya'' is a tiny species of saltwater clam, a marine bivalve mollusk or micromollusk in the family Nuculidae, the nut clams. This species grows to a length of about and is believed to be the smallest living bivalve.

'' grows long.

Gastropods (Gastropoda)

The smallest water

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class ...

(of all snails) is '' Ammonicera minortalis'' in North America, originally described from Cuba. It measures . The smallest land snail is '' Acmella nana''. Discovered in

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and e ...

, and described in November 2015, it measures . The previous record was that of '' Angustopila dominikae'' from China, which was reported in September 2015. This snail measures .

Cephalopods (Cephalopoda)

'' Maximites'' was the smallest known

ammonoid Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

. Adult specimens reached only in shell diameter.

Arthropods (Arthropoda)

Arachnids (Arachnida)

* There is a debate about which

spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

is smallest. According to Guinness World Records, "Two contenders are from the

Symphytognathidae Symphytognathidae is a family of spiders with 90 described species in eight genera. They occur in the tropics of Central and South America and the Australian region (with Oceania). Exceptions include '' Anapistula benoiti'', '' Anapistula caecu ...

genus '' Patu'': males of '' Patu digua'' described in Colombia had a body length of , while the Samoan moss spider ( ''P. marplesi'') could be as small as 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 and respectively. Males of both species are potentially smaller than the females, but no ''Anapistula ataecina or Anapistula caecula'' have been measured yet. * '' Cochlodispus minimus'' is the smallest mite. An adult individual measured with a body length of . However, PBS claims "The tiniest mite on record is 82 microns long" but does not name a species.

Non-hexapod crustaceans (Crustacea)

The smallest

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

is the tantulocarid '' Stygotantulus stocki'', at a length of .

Insects (Insecta)

* Adult males of the parasitic

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

Dicopomorpha echmepterygis ''Dicopomorpha echmepterygis'' is the smallest known insect and a species of parasitoid wasp in the family Mymaridae, which exhibits strong sexual dimorphism. The males are blind, apterous, and their body length is only 40% that of females. Wit ...

'' can be as small as long, smaller than some species of protozoa (single-cell creatures); females are 40% larger. '' Megaphragma caribea'' from

Guadeloupe Guadeloupe (; ; gcf, label= Antillean Creole, Gwadloup, ) is an archipelago and overseas department and region of France in the Caribbean. It consists of six inhabited islands— Basse-Terre, Grande-Terre, Marie-Galante, La Désirade, and ...

, measuring long, is another contender for smallest known insect in the world. *

Beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s of the tribe Nanosellini are all less than long; the smallest confirmed specimen is of ''

Scydosella musawasensis ''Scydosella'' is a genus of beetles that consists of only one species ''Scydosella musawasensis''. The species is regarded as the smallest free-living insect, as well as the smallest beetle. They are among featherwing beetle, named because of ...

'' at 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. Grand Cayman pygmy blue (Brephidium exilis thompsoni) 2

Grand Cayman pygmy blue (Brephidium exilis thompsoni) 2

* The western pygmy blue (''Brephidium exilis'') is one of the smallest

butterflies Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprises ...

in the world, with a wingspan of about .

Echinoderms (Echinodermata)

The smallest

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuri ...

, and also the smallest

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

, is ''Psammothuria ganapati'', a synaptid that lives between sand grains on the coast of India. Its maximum length is .

Sea urchins

The smallest

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) o ...

, ''Echinocyamus scaber'', has a

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

across.

Starfish

'' Patiriella parvivipara'' is the smallest

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish a ...

, at across.

Fish (Pisces)

* One of the smallest

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

and the smallest fish based on the minimum size at maturity is ''

Paedocypris progenetica ''Paedocypris progenetica'' is a species of tiny cyprinid fish endemic to the Indonesian islands of Sumatra and Bintan where it is found in peat swamps and blackwater streams. It was discovered by Singaporean ichthyologist Heok Hui Tan. He ha ...

'' from

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...

, with mature females measuring as little as in standard length. 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 ''Schindleria brevipinguis'' is a species of marine fish in family Gobiidae of Perciformes. Known as the stout infantfish, it is native to Australia's Great Barrier Reef and to Osprey Reef in the Coral Sea. Anatomy ''S. brevipinguis'' is among t ...

'' from Australia, their females reach and males . Males of ''S. brevipinguis'' have an average standard length of ; a gravid female was . This fish, a member of the goby family, differs from similar members of the group in having its first

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...

ray further forward, under

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

4. * Male individuals of the

anglerfish The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence ...

species ''

Photocorynus spiniceps ''Photocorynus spiniceps'' is a species of anglerfish in the family Linophrynidae. It is in the monotypic genus ''Photocorynus''. The known mature male individuals are 6.2–7.3 millimeters (0.25-0.3 inches), smaller than any other ma ...

'' have been documented to be 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 .

Amphibians (Amphibia)

Frogs and toads (Anura)

Paratype of Paedophryne amauensis (LSUMZ 95004)

The smallest

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

s (and smallest amphibians) known are ''

Paedophryne amauensis ''Paedophryne amauensis'' is a species of microhylid frog endemic to eastern Papua New Guinea. At in snout-to-vent length, it is considered the world's smallest known vertebrate. (See also Ecological guild.) The species was listed in the ...

'' frogs from Papua New Guinea, which range in length from , and average . Other very small frogs include '' Brachycephalus didactylus'' from Brazil (reported as ), several species of ''

Eleutherodactylus ''Eleutherodactylus'' is a genus of frogs in the family Eleutherodactylidae.Hedges, S. B., W. E. Duellman, and M. P. Heinicke . 2008. New World direct-developing frogs (Anura: Terrarana): molecular phylogeny, classification, biogeography, and c ...

'' such as '' E. iberia'' (around ) and '' E. limbatus'' () and ''

Eleutherodactylus orientalis ''Eleutherodactylus orientalis'', the Oriental robber frog or Baracoa dwarf frog, is a species of frog in the family Eleutherodactylidae. It is endemic to the vicinity of El Yunque, Baracoa, in easternmost Cuba. Although locally common, it requ ...

'' () from Cuba, Gardiner's Frog ''

Sechellophryne gardineri Gardiner's Seychelles frog (''Sechellophryne gardineri'') is a small frog of the family Sooglossidae and endemic to the Seychelles. It is named after John Stanley Gardiner, English zoologist and oceanographer. Description Gardiner's frog is one ...

'' from the Seychelles (up to ), several species of ''

Stumpffia ''Stumpffia'' is a genus of microhylid frogs that are endemic to Madagascar. They are mostly brown frogs that typically live among leaf litter. ''S. contumelia'' has a snout–vent length of about , making it one of the world's smallest frogs, a ...

'' such as '' S. tridactyla'' () and '' S. pygmaea'' (males ; females: ) and '' Wakea madinika'' (males: ; females: ) from Madagascar. '' Paedophryne swiftorum'' (body length ) is not included in the smallest vertebrates known with other nine species of frogs. The two species '' Microhyla borneensis'' (males: ; females: ) and '' Arthroleptella rugosa'' (males: ; females: ) were once the smallest known frogs from the

Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by thei ...

. 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 ''Thorius arboreus'', commonly known as the arboreal minute salamander, is a species of salamander in the family Plethodontidae. It is endemic to Sierra de Juarez, Oaxaca, Mexico. The specific name ''arboreus'', derives from the Latin word ''a ...

'' was .

Sauropsids (Sauropsida)

Lizards and snakes (Squamata)

* The dwarf gecko (''Sphaerodactylus ariasae'') is the smallest known

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchocephalia ...

species and smallest lizard, with a snout-vent length of . ''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 The Dominican Republic ( ; es, República Dominicana, ) is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean region. It occupies the eastern five-eighths of the island, which it shares with ...

and on

Beata Island Beata Island ( es, Isla Beata) is a small island on the Caribbean Sea, located southwest from Cape Beata. Some southwest of it lies the smaller Alto Velo Island. It is politically part of the Dominican Republic, and is roughly triangle-shaped a ...

(''Isla Beata''), off the southern coast of the

. A few ''

Brookesia ''Brookesia'' is a genus of chameleons, endemic to Madagascar, that range from small to very small in size, and are known collectively as leaf chameleons (though this name also commonly is used for species in the genera ''Rieppeleon'' and ''Rham ...

'' chameleons from

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...

are equally small, with a reported snout-vent length of for male dwarf chameleons ('' B. minima''), for male Mount d'Ambre leaf chameleons ('' B. tuberculata'') and for male '' B. micra'', though females are larger. In 2021, a new species of ''

'', '' B. nana'', was discovered, with a snout-vent length of , possibly making it the smallest known reptile. Leptotyphlops carlae

* One of the smallest known

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...

s is the recently discovered

Barbados threadsnake The Barbados threadsnake (''Tetracheilostoma carlae'') is a species of threadsnake. It is the smallest known snake species. This member of the Leptotyphlopidae family is found on the Caribbean islands of Barbados and Anguilla. Taxonomy and ety ...

(''Leptotyphlops carlae''). Adults average about long, which is only about twice as long as the

hatchling In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well. Fish Fish hatchlings generally do not receive parental care, similar to ...

s. The Common blind snake (''Indotyphlops braminus'') measures long, occasionally up to long.

Turtles and tortoises (Testudines)

The smallest

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

is the speckled padloper tortoise (''Homopus signatus'') from

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

. The males measure , while females measure up to almost .

Crocodiles and close relatives (Crocodylomorpha)

* The smallest extant

crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest livin ...

is the Cuvier's dwarf caiman (''Paleosuchus palpebrosus'') from northern and central South America. It reaches up to in length. * Some extinct

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cro ...

s were even smaller. Fully grown ''

Bernissartia ''Bernissartia'' ('of Bernissart') is an extinct genus of neosuchian crocodyliform that lived in the Early Cretaceous, around 130 million years ago. At only in length, ''Bernissartia'' is one of the smallest crocodyliforms that ever lived. ...

'' from the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145& ...

reached a bit more than in length. * The

terrestrial notosuchian '' Malawisuchus'' was no more than long. Other small notosuchians include '' Anatosuchus'' at and herbivorous ''

Simosuchus ''Simosuchus'' (meaning "pug-nosed crocodile" in Greek, referring to the animal's blunt snout) is an extinct genus of notosuchian crocodylomorphs from the Late Cretaceous of Madagascar. It is named for its unusually short skull. Fully grown indi ...

'' at .

Pterosaurs (Pterosauria)

Nemicolopterus ''Nemicolopterus'' is a genus of tapejaromorph pterosaur, based on a very small specimen described as the smallest known "adult" pterosaur to date. It lived in the Jehol Biota 120 million years ago. Discovery and naming The generic name "Nemi ...

'' was the smallest pterosaur, it reached about in wingspan.

Non-avian dinosaurs (Dinosauria)

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

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

is ''

Anchiornis ''Anchiornis'' is a genus of small, four-winged paravian dinosaurs, with only one known species, the type species ''Anchiornis huxleyi'', named for its similarity to modern birds. The Latin name ''Anchiornis'' derives from a Greek word meaning " ...

'', 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 long, and the weight has been estimated at up to . '' Parvicursor'' was initially seen as one of the smallest non-avian dinosaurs known from an adult specimen, at in length, and in weight. However, in 2022 its

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

was concluded to represent a juvenile individual. '' Epidexipteryx'' reached in length and in weight.

Birds (Aves)

* With a mass of approximately and a length of , the

bee hummingbird The bee hummingbird, zunzuncito or Helena hummingbird (''Mellisuga helenae'') is a species of hummingbird, native to the island of Cuba in the Caribbean. It is the world's smallest bird. Description The bee hummingbird is the smallest living ...

(''Mellisuga helenae'') is the smallest known dinosaur as well as the smallest

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

species, and the smallest

warm-blooded Warm-blooded is an informal term referring to animal species which can maintain a body temperature higher than their environment. In particular, homeothermic species maintain a stable body temperature by regulating metabolic processes. The on ...

. Called the ''zunzuncito'' in its native habitat on Cuba, it is lighter than a

Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...

U.S. penny The cent, the United States one-cent coin (symbol: ¢), often called the "penny", is a unit of currency equaling one one-hundredth of a United States dollar. It has been the lowest face-value physical unit of U.S. currency since the abolition ...

. It is said that it is "more apt to be mistaken for a

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfami ...

than a bird". The bee hummingbird eats half its total

body mass Human body weight is a person's mass or weight. Strictly speaking, body weight is the measurement of weight without items located on the person. Practically though, body weight may be measured with clothes on, but without shoes or heavy accesso ...

and drinks eight times its total body mass each day. Its nest is across. * The smallest

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which ...

pygmy goose The pygmy geese are a group of very small " perching ducks" in the genus ''Nettapus'' which breed in the Old World tropics. They are the smallest of all wildfowl. As the "perching ducks" are a paraphyletic group, they need to be placed elsewhere ...

(''

Nettapus The pygmy geese are a group of very small "perching ducks" in the genus ''Nettapus'' which breed in the Old World tropics. They are the smallest of all wildfowl. As the "perching ducks" are a paraphyletic group, they need to be placed elsewhere ...

''). African species reaches the average weight of about for males and for females and wingspans between and . The second smallest waterfowl is the extinct ''

Mioquerquedula ''Mioquerquedula'' is an extinct genus of ducks from the Middle Miocene containing two species, ''M. minutissima'' and ''M. velox''. It was one of the smallest anseriforms known. The genus was erected by Nikita Zelenkov and Evgenii Nikolaievich ...

'' from the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

. * The smallest

penguin Penguins (order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adap ...

species is the

little blue penguin The little penguin (''Eudyptula minor'') is a species of penguin from New Zealand. They are commonly known as little blue penguins or blue penguins owing to their slate-blue plumage and are also known by their Māori name . The Australian lit ...

(''Eudyptula minor''), which stands around tall and weighs .

Non-mammalian synapsids (Synapsida)

The smallest

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

mammaliaform was ''

Hadrocodium ''Hadrocodium wui'' is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately in the Lufeng Formation of the Lufeng Basin in what is now the Yunnan province in south-western China (, paleocoordina ...

'' with a skull of in length and a body mass of .

Mammals (Mammalia)

Marsupials (Marsupialia)

The smallest

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in ...

is the long-tailed planigale from Australia. It has a body length of (including tail) and weigh on average. The Pilbara ningaui is considered to be of similar size and weight.

Shrews (Eulipotyphla)

The

Etruscan shrew The Etruscan shrew (''Suncus etruscus''), also known as the Etruscan pygmy shrew or the white-toothed pygmy shrew, is the smallest known extant mammal by mass, weighing only about on average. (The bumblebee bat is regarded as the smallest mamma ...

(''Suncus etruscus''), is the smallest mammal by mass, weighing about on average. The smallest mammal that ever lived, the shrew-like ''

Batodonoides vanhouteni ''Batodonoides vanhouteni'' is an extinct shrew-like mammal, thought to be the smallest mammal that ever lived, as well as the smallest synapsid that ever lived. Based on the size of its molar teeth, it is estimated that ''Batodonoides vanhouten ...

'', weighed .

Bats (Chiroptera)

The vulnerable Kitti's hog-nosed bat (''Craseonycteris thonglongyai''), also known as the bumblebee bat, from

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

and

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

is the smallest

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

, at in length and in weight.

Carnivorans (Carnivora)

The smallest member of the order

Carnivora Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...

is the

least weasel The least weasel (''Mustela nivalis''), little weasel, common weasel, or simply weasel is the smallest member of the genus '' Mustela,'' family Mustelidae and order Carnivora. It is native to Eurasia, North America and North Africa, and has be ...

(''Mustela nivalis''), with an average body length of . It weighs between with females being lighter.

Rodents (Rodentia)

The smallest known member of the

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

order is the

Baluchistan pygmy jerboa The Baluchistan pygmy jerboa (''Salpingotulus michaelis'') or dwarf three-toed jerboa, is a species of rodent in the family Dipodidae. It is the only species in the genus ''Salpingotulus''. Adults average only in head and body length, with the t ...

, with an average body length of .

Primates (Primates)

The smallest member of the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

is Madame Berthe's mouse lemur (''Microcebus berthae''), found in

, with an average body length of .

Cetaceans (Cetacea)

The smallest

cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel th ...

n, which is also (as of 2006) the most endangered, is the

vaquita The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...

, a species of porpoise. Male vaquitas grow to an average of around ; the females are slightly longer, averaging about in length.

Plants (Plantae)

Gymnosperms (Gymnospermae)

'' Zamia pygmaea'' is a

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male o ...

found in Cuba, and the smallest known

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...

. It grows to a height of .

Angiosperms (Angiospermae)

Duckweed Lemnoideae is a subfamily of flowering aquatic plants, known as duckweeds, water lentils, or water lenses. They float on or just beneath the surface of still or slow-moving bodies of fresh water and wetlands. Also known as bayroot, they arose f ...

s of the genus ''

Wolffia ''Wolffia'' is a genus of aquatic plants with a cosmopolitan distribution. They include the smallest flowering plants on Earth. Commonly called watermeal or duckweed, these aquatic plants resemble specks of cornmeal floating on the water. Indivi ...

'' are the smallest

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...

s. Fully grown, they measure and reach a mass of just 150 µg.

Dicotyledons

The smallest known

dicotyledon The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

plant is the Himalayan dwarf mistletoe (''Arceuthobium minutissimum''). Shoots grow up to in height.

Other

Nanobes

Nanobes are thought by some scientists to be the smallest known organisms, about one tenth the size of the smallest known bacteria. Nanobes, tiny filamental structures first found in some rocks and

sediments Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

, were first described in 1996 by Philippa Uwins of the

University of Queensland , mottoeng = By means of knowledge and hard work , established = , endowment = A$224.3 million , budget = A$2.1 billion , type = Public research university , chancellor = Peter Varghese , vice_chancellor = Deborah Terry , city = B ...

, but it is unclear what they are, and if they are alive.

References

{{Reflist, colwidth=30em

External links

Featherwing beetles
on the UF / IFAS Featured Creatures Web site Organism size Biological records es:Tamaño de los seres vivos