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

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

size, including

volume Volume is a measure of regions in 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 and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

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 an example of vertical extent, "This basketball player is 7 foot 1 inches in height." For an e ...

length Length is a measure of distance. In the International System of Quantities, length is a quantity with Dimension (physical quantity), dimension distance. In most systems of measurement a Base unit (measurement), base unit for length is chosen, ...

, or

genome 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 genes, other functional regions of the genome such as ...

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, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...

, 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 Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biological interaction, between two organisms of different species. The two organisms, termed symbionts, can fo ...

of the European pest leafhopper, '' Macrosteles quadripunctulatus'', consists of a circular chromosome of 112,031 base pairs. The genome of '' Nanoarchaeum equitans'' is 491 Kbp 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'' (also known as ''MG','' Mgen, or since 2018, ''Mycoplasmoides genitalium'') is a sexually transmitted, small and pathogenic bacterium that lives on the mucous epithelial cells of the urinary and genital tracts in ...

'', a parasitic

bacterium Bacteria (; : 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 among the ...

which lives in the

primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

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

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: Asexual reproduction, asexual and Sexual ...

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

. 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 Mathematics, 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 element, maximal Filter (mathematics), filter on P; that is, a proper filter on P th ...

. 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 excret ...

''Nanoarchaeum''

'' Nanoarchaeum equitans'' is a species of

microbe A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...

in diameter. It was discovered in 2002 in a

hydrothermal vent Hydrothermal vents are fissures 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 hot ...

off the coast of

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

by Karl Stetter. A

thermophile A thermophile is a type of extremophile that thrives at relatively high temperatures, between . Many thermophiles are archaea, though some of them are bacteria and fungi. Thermophilic eubacteria are suggested to have been among the earliest bacte ...

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

on the archaeon '' Ignicoccus''; 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 British reference book published annually, list ...

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

Single-celled Eukaryotes (protists)

Prasinophyte algae of the genus '' Ostreococcus'' are the smallest free-living

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

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

Heliozoa

The ''Erebor'' lineage of '' Microheliella maris'' is the smallest known heliozoan with an average cell body diameter of 2.56 μm.

Diatoms

The smallest

diatoms A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

with diameters as small as 1.9 μm can be found in the genera '' Mediolabrus'' and '' Minidiscus.'' '' Mediolabrus comicus'' is the smallest known marine diatom.

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 (biology), cell, a multicellular organism, or a Community (ecology), community of Biological inter ...

s consider

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

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 Nucleic acids are large biomolecules that are crucial in all cells and viruses. They are composed of nucleotides, which are the monomer components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main classes of nucleic aci ...

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 (physical form and structure), its developmental processes, its biochemical and physiological propert ...

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 virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that Capsid, encapsulate a DNA or RNA genome, and may have structu ...

Phi-X174 with a genome size of 5,386

nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

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 m ...

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 virus characterized by a ribonucleic acid (RNA) based genome. The genome can be single-stranded RNA (ssRNA) or double-stranded (Double-stranded RNA, dsRNA). Notable human diseases caused by RNA viruses include influenza, SARS, ...

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. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase e ...

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

obelisks An obelisk (; , diminutive of (') ' rotisserie, spit, nail, pointed pillar') is a tall, slender, tapered monument with four sides and a pyramidal or pyramidion top. Originally constructed by Ancient Egyptians and called Obelisk (hieroglyph), ...

, ribozymes, satelliviruses and

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 eco ...

Animals (Animalia)

Several species of Myxozoa (obligately parasitic

cnidarian Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

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 (Mollusca)

Bivalvia

The shell of the nut clam '' Condylonucula maya'' grows long.

Gastropods (Gastropoda)

The smallest water

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

(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 () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

, 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. Adult specimens reached only in shell diameter.

Arthropods (Arthropoda)

The smallest arthropods are

mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...

s '' Cochlodispus minimus'' of the family Microdispidae. The body length of the smallest measured individual was .

Crustaceans (Crustacea)

The smallest

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s belong to the class Tantulocarida. The single smallest species may be '' Tantulacus dieteri'', with a total body length of only . Another candidate is '' Stygotantulus stocki'', with a length of .

Arachnids (Arachnida)

* There is a debate about which

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

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 , 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 male ''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.

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

Guadeloupe Guadeloupe is an Overseas departments and regions of France, overseas department and region of France in the Caribbean. It consists of six inhabited islands—Basse-Terre Island, Basse-Terre, Grande-Terre, Guadeloupe, Grande-Terre, Marie-Galant ...

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

Beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s of the tribe Nanosellini are all less than long; the smallest confirmed specimen is of '' Scydosella musawasensis'' 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. * The western pygmy blue (''Brephidium exilis'') is one of the smallest

butterflies Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...

in the world, with a wingspan of about .

Echinoderms (Echinodermata)

The smallest

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

, and also the smallest

echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...

, 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 or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

, ''Echinocyamus scaber'', has a test across.

Starfish

'' Patiriella parvivipara'' is the smallest

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

, at across.

Fish

* One of the smallest

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

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

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, with mature females measuring as little as in

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

. 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 and males . Males of ''S. brevipinguis'' have an average

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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

ray further forward, under

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

4. * Male individuals of the

anglerfish The anglerfish are ray-finned fish in the order Lophiiformes (). Both the order's common name, common and scientific name comes from the characteristic mode of predation, in which a modified dorsal Fish fin#Ray-fins, fin ray acts as a Aggressiv ...

species ''

Photocorynus spiniceps ''Photocorynus'' is a monospecific genus of marine life, marine Actinopterygii, ray-finned fish belonging to the family leftvent, Linophrynidae, the leftvents. The only species in the genus is ''Photocorynus spiniceps''. ''Photocorynus'' was fi ...

'' 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)

The smallest

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

(and smallest amphibian) known is '' Brachycephalus pulex'', a Brazilian flea toad, with a minimum adult snout–vent length of . ''

Brachycephalus dacnis ''Brachycephalus dacnis'' is a species of small frogs in the family Brachycephalidae endemic to the Atlantic Forest of Brazil. It is one of more than 40 named species within the genus ''Brachycephalus'', and is most similar to ''Brachycephalus he ...

'' is similarly tiny, with a minimum adult length of . Other very small frogs include: * '' Paedophryne amauensis'' from Papua New Guinea, ranging in length from , and on average. * '' Brachycephalus didactylus'' from Brazil (reported as ) * several species of '' Eleutherodactylus'' such as '' E. iberia'' (around ) and '' E. limbatus'' () and '' Eleutherodactylus orientalis'' () from Cuba, * Gardiner's Frog '' Sechellophryne gardineri'' from the Seychelles (up to ), * several species of '' Stumpffia'' such as '' S. tridactyla'' () and '' S. pygmaea'' (males ; females: ) and '' Wakea madinika'' (males: ; females: ) from Madagascar. 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 coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...

. 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 .

Sauropsids (Sauropsida)

Lizards and snakes (Squamata)

* The miniature chameleon '' Brookesia nana'', with a snout-vent length of , may represent the smallest known lizard and smallest reptile. * The dwarf gecko (''Sphaerodactylus ariasae'') is also one of the smallest known

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

species, 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 is a country located on the island of Hispaniola in the Greater Antilles of the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean. It shares a Maritime boundary, maritime border with Puerto Rico to the east and ...

and on Beata Island (''Isla Beata''), off the southern coast of the

. A few '' Brookesia'' chameleons from

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

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. Leptotyphlops carlae

* One of the smallest known

snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

s is the recently discovered

Barbados threadsnake The Barbados threadsnake (''Tetracheilostoma carlae'') is a species of Leptotyphlopidae, threadsnake. It is the smallest known snake species. This member of the Leptotyphlopidae Family (biology), family is found on the Caribbean islands of Barbad ...

(''Leptotyphlops carlae''). Adults average about long, which is only about twice as long as the hatchlings. The Common blind snake (''Indotyphlops braminus'') measures long, occasionally up to long.

Turtles and tortoises (Testudines)

The smallest

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

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

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

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

Archosaurs (Archosauria)

Crocodiles and close relatives (Crocodylomorpha)

* The smallest extant

crocodilian Crocodilia () is an Order (biology), order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorp ...

is the Cuvier's dwarf caiman (''Paleosuchus palpebrosus'') from northern and central South America. It reaches up to in length. * Some extinct crocodylomorphs were even smaller. Fully grown '' Bernissartia'' 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 143.1 ...

reached a bit more than in length. * The

terrestrial

notosuchia Notosuchia is a clade of primarily Gondwanan mesoeucrocodylian Crocodylomorpha, crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogeny, phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group ...

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

Pterosaurs (Pterosauria)

'' Nemicolopterus'' 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 non-avian

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

is ''

Anchiornis ''Anchiornis'' is a genus of small, four-winged Paraves, 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 m ...

'', a genus of feathered dinosaur that lived in what is now China during the Late

Jurassic Period The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. The Jurassic constitutes the second and m ...

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 (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

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 smallest known bird. The bee hummingbird feeds on nectar of flowers and bugs foun ...

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

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

species, and the smallest

warm-blooded Warm-blooded is a term referring to animal species whose bodies maintain a temperature higher than that of their environment. In particular, homeothermic species (including birds and mammals) maintain a stable body temperature by regulating ...

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

Canadian Canadians () 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 their being ''C ...

or U.S. penny. It is said that it is "more apt to be mistaken for a bee than a bird". The bee hummingbird eats half its total body mass 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 i ...

is pygmy goose ('' Nettapus''). African species reaches the average weight of about for males and for females and length of single wing between and . The second smallest waterfowl is the extinct '' Mioquerquedula'' from the

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

. * The smallest

penguin Penguins are a group of aquatic flightless birds from the family Spheniscidae () of the order Sphenisciformes (). They live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, is equatorial, with a sm ...

species is the little blue penguin (''Eudyptula minor''), which stands around tall and weighs . * The smallest bird of prey is the Black-thighed falconet (''Microhierax fringillarius''), with a

wingspan The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the opposite wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingsp ...

of , roughly the size of a sparrow.Raptors of the World by Ferguson-Lees, Christie, Franklin, Mead & Burton. Houghton Mifflin (2001)828-829,

Non-mammalian synapsids (Synapsida)

The smallest

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

mammaliaform Mammaliaformes ("mammalian forms") is a clade of synapsid tetrapods that includes the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts during the Late Triassic. It is defined a ...

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

Mammals (Mammalia)

Marsupials (Marsupialia)

The smallest

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

is the long-tailed planigale from Australia. It has a body length of (including tail) and weighs 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, white-toothed pygmy shrew and Savi's pygmy shrew, is the smallest known extant mammal by mass, weighing only about on average. (The bumblebee bat is regarded as t ...

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

Bats (Chiroptera)

The

Kitti's hog-nosed bat Kitti's hog-nosed bat (''Craseonycteris thonglongyai''), also known as the bumblebee bat, is a near-threatened species of bat and the only extant member of the family Craseonycteridae. It occurs in western Thailand and southeast Myanmar, where it ...

(''Craseonycteris thonglongyai''), also known as the bumblebee bat, from

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

and

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

is the smallest

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

, at in length and in weight.

Carnivorans (Carnivora)

The smallest member of the order

Carnivora Carnivora ( ) is an order of placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 279 species. Carnivor ...

is the least weasel (''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 (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

order is the Baluchistan pygmy jerboa, with an average body length of .

Primates (Primates)

The smallest member of the

order 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 belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

n, which is also (as of 2006) the most endangered, is the vaquita, a species of porpoise. Male vaquitas grow to an average of around ; the females are slightly longer, averaging about in length.

Embryophytes (Embryophyta)

Gymnosperms (Gymnospermae)

'' Zamia pygmaea'' is a

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

found in Cuba, and the smallest known

gymnosperm The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetoph ...

. It grows to a height of .

Angiosperms (Angiospermae)

Duckweeds of the genus '' Wolffia'' are the smallest

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed within a fruit ...

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

μg In the metric system, a microgram or microgramme is a Physical unit, unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and Uni ...

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, ...

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 solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

, were first described in 1996 by Philippa Uwins of the

University of Queensland The University of Queensland is a Public university, public research university located primarily in Brisbane, the capital city of the Australian state of Queensland. Founded in 1909 by the Queensland parliament, UQ is one of the six sandstone ...

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

Notes

References

Other references

* *

External links

Featherwing beetles
on the UF / IFAS Featured Creatures Web site {{Records * es:Tamaño de los seres vivos

Microorganisms

Obligate endosymbiotic bacteria

''Pelagibacter ubique''

''Mycoplasma genitalium''

''Nanoarchaeum''

Single-celled Eukaryotes (protists)

Heliozoa

Diatoms

Viruses

Animals (Animalia)

Molluscs (Mollusca)

Bivalvia

Gastropods (Gastropoda)

Cephalopods (Cephalopoda)

Arthropods (Arthropoda)

Crustaceans (Crustacea)

Arachnids (Arachnida)

Insects (Insecta)

Echinoderms (Echinodermata)

Sea urchins

Starfish

Fish

Amphibians (Amphibia)

Frogs and toads (Anura)

Salamanders, newts and allies (Urodela)

Sauropsids (Sauropsida)

Lizards and snakes (Squamata)

Turtles and tortoises (Testudines)

Archosaurs (Archosauria)

Crocodiles and close relatives (Crocodylomorpha)

Pterosaurs (Pterosauria)

Non-avian dinosaurs (Dinosauria)

Birds (Aves)

Non-mammalian synapsids (Synapsida)

Mammals (Mammalia)

Marsupials (Marsupialia)

Shrews (Eulipotyphla)

Bats (Chiroptera)

Carnivorans (Carnivora)

Rodents (Rodentia)

Primates (Primates)

Cetaceans (Cetacea)

Embryophytes (Embryophyta)

Gymnosperms (Gymnospermae)

Angiosperms (Angiospermae)

Dicotyledons

Other

Nanobes

See also

Notes

References

Other references

External links