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

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

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). Th ...

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 element ...

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 Cell signaling, signaling and self-sustaining processes, from that which does not, and is defined by the capacity for Cell growth, growth, reaction to Stimu ...

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

Microorganisms

Obligate endosymbiotic bacteria

The genome of ''

Nasuia deltocephalinicola ''Nasuia deltocephalinicola'' was reported in 2013 to have the smallest genome of all bacteria, with 112,091 nucleotides. For comparison, the human genome has 3.2 billion nucleotides. The second smallest genome, from bacteria '' Tremblaya princep ...

'', a

symbiont Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or paras ...

of the European pest leafhopper, '' Macrosteles quadripunctulatus'', consists of a circular chromosome of 112,031 base pairs. The genome of '' Nanoarchaeum equitans'' 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

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 a ...

which lives in the

primate Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...

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 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. 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 excr ...

''Nanoarchaeum''

'' Nanoarchaeum equitans'' is a species of microbe in diameter. It was discovered in 2002 in a hydrothermal vent 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 ...

by Karl Stetter. 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

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 reference book published annually, listing world ...

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

Eukaryotes (Eukaryota)

Prasinophyte

alga Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...

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. Bact ...

. 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 speciali ...

s consider

virus A virus is a wikt:submicroscopic, 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 ...

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 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 possible that the smalle ...

, 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 or physical form and structure, its developmental processes, its biochemical and physiological prop ...

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". Bact ...

Phi-X174 The phi X 174 (or ΦX174) bacteriophage is a single-stranded DNA ( ssDNA) virus that infects ''Escherichia coli'', and the first DNA-based genome to be sequenced. This work was completed by Fred Sanger and his team in 1977. In 1962, Walter Fi ...

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 biomolecul ...

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 may ...

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 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 transcriptase ...

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

hepadnaviruses ''Hepadnaviridae'' is a family of viruses. Humans, apes, and birds serve as natural hosts. There are currently 18 species in this family, divided among 5 genera. Its best-known member is hepatitis B virus. Diseases associated with this family i ...

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. F ...

, 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 econo ...

s and ribozymes.

Animals (Animalia)

Several species of Myxozoa (obligately parasitic

cnidarian Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in Fresh water, freshwater and Marine habitats, marine environments, predominantly the latter. Their distinguishing feature is cnidocyt ...

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'' 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 G ...

(of all snails) is ''

Ammonicera minortalis ''Ammonicera'' is a genus of minute sea snails, marine gastropod molluscs or micromollusks in the family Omalogyridae.Bouchet, P.; Gofas, S. (2012). ''Ammonicera'' Vayssière, 1893. Accessed through: World Register of Marine * At http://www.marin ...

'' in North America, originally described from Cuba. It measures . The smallest land snail is ''

Acmella nana ''Acmella nana'' is a species of land snail discovered from Borneo, Malaysia, in 2015. It was described by Jaap J. Vermeulen of the JK Art and Science in Leiden, Thor-Seng Liew of the Institute for Tropical Biology and Conservation at the Univers ...

''. Discovered in

Borneo Borneo (; id, Kalimantan) is the List of islands by area, 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 Isl ...

, 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 ''Maximites'' is a genus of Pennsylvanian (geology), Late Carboniferous ammonoids. Adult specimens were smallest organisms, the smallest known ammonoids, only at about in diameter of shells. Fossils are found in various Late Carboniferous marin ...

'' was the smallest known ammonoid. 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 d ...

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 ''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 decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

is the

tantulocarid Tantulocarida is a highly specialised group of parasitic crustaceans that consists of about 33 species, treated as a class in superclass Multicrustacea. They are typically ectoparasites that infest copepods, isopods, tanaids, amphipods and os ...

'' Stygotantulus stocki'', at a length of .

Insects (Insecta)

* Adult males of the parasitic wasp '' Dicopomorpha echmepterygis'' can be as small as long, smaller than some species of protozoa (single-cell creatures); females are 40% larger. ''

Megaphragma caribea ''Megaphragma caribea'' is a species of wasp. It has been found acting as an egg parasitoid of ''Heliothrips haemorrhoidalis ''Heliothrips haemorrhoidalis'' is a species of thrips in the family Thripidae. It is most commonly known as the green ...

'' 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 the ...

, 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 t ...

in the world, with a wingspan of about .

Echinoderms (Echinodermata)

The smallest sea cucumber, 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 s ...

, 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) ...

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

Starfish

'' Patiriella parvivipara'' is the smallest starfish, at across.

Fish (Pisces)

* One of the smallest vertebrates 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 and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

, 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'' 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 s ...

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 species '' Photocorynus spiniceps'' have been documented to be at maturity, and thus claimed to be a smaller species. However, these survive only by

sexual parasitism Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. There may also be a range of secondary organs that increase reproductive fitness. The geni ...

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 taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

s (and smallest amphibians) known are '' Paedophryne amauensis'' frogs from Papua New Guinea, which range in length from , and average . Other very small frogs include ''

Brachycephalus didactylus The Brazilian gold frog (''Brachycephalus didactylus''), also known as Izecksohn's toad or flea-frog, is a very small species of frogs in the family Brachycephalidae. It is endemic to southeastern Brazil and is known from the central part of the ...

'' 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 ''Wakea madinika'' is a species of frogs in the mantellid subfamily Mantellinae. It is the only species in the monotypic genus ''Wakea''. It is endemic to Madagascar. Discovery ''Wakea madinika'' reaches males snout-vent length and females l ...

'' (males: ; females: ) from Madagascar. ''

Paedophryne swiftorum ''Paedophryne swiftorum'' is a species of frog from Papua New Guinea discovered in 2008 and formally described in January 2012. It lives among leaf litter on the tropical rainforest floor and was named after the Swift family who had provided fun ...

'' (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 ''Arthroleptella rugosa'' is a species of frog in the family Pyxicephalidae. It is endemic to South Africa and only known from the Klein Swartberg Mountain, an inselberg near Caledon, Western Cape. The specific name ''rugosa'' is Latin for ''w ...

'' (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 th ...

. 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 ''arb ...

'' was .

Sauropsids (Sauropsida)

Lizards and snakes (Squamata)

* The dwarf gecko (''Sphaerodactylus ariasae'') is the smallest known reptile 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 (''Isla Beata''), off the southern coast of the

. A few '' Brookesia'' 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 Africa ...

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 '' Brookesia'', '' 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 j ...

s is the recently discovered Barbados threadsnake (''Leptotyphlops carlae''). Adults average about long, which is only about twice as long as the hatchlings. The

Common blind snake ''Indotyphlops braminus'', commonly known as the brahminy blind snake and other names, is a non-venomous blind snake species found mostly in Africa and Asia, but has been introduced in many other parts of the world. They are completely fossorial ...

(''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 ...

is the

speckled padloper tortoise ''Chersobius signatus'' is the world's smallest species of tortoise (family Testudinidae). The species is commonly known as the speckled tortoise and also known locally as the speckled padloper and internationally as the speckled Cape 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 count ...

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

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 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. It ...

'' from the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

reached a bit more than in length. * The

terrestrial notosuchian ''

Malawisuchus ''Malawisuchus'' (meaning "Malawi crocodile") is an extinct genus of notosuchian mesoeucrocodylian from the Early Cretaceous Dinosaur Beds of Malawi. It was described in 1997 by Elizabeth Gomani as a member of the family Notosuchidae. The type ...

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

or U.S. penny. 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 monophyly, monophyletic lineage within the ...

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 is

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''). 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 K ...

'' 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 recent" ...

. * The smallest penguin species is the little blue penguin (''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 Creta ...

mammaliaform was '' Hadrocodium'' 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 a ...

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 (''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 vanhoute ...

'', weighed .

Bats (Chiroptera)

The

vulnerable Vulnerable may refer to: General * Vulnerability * Vulnerability (computing) * Vulnerable adult * Vulnerable species Music Albums * ''Vulnerable'' (Marvin Gaye album), 1997 * ''Vulnerable'' (Tricky album), 2003 * ''Vulnerable'' (The Used album) ...

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, at in length and in weight.

Carnivorans (Carnivora)

The smallest member of the order Carnivora 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 lower jaws. About 40% of all mammal species are roden ...

order is the Baluchistan pygmy jerboa, 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 d ...

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

, with an average body length of .

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 ; the females are slightly longer, averaging about in length.

Plants (Plantae)

Gymnosperms (Gymnospermae)

Zamia pygmaea ''Zamia pygmaea'' is a species of plant in the family Zamiaceae found only in Cuba. It is the smallest living cycad. It is listed as critically endangered on the IUCN Red List based on its limited distribution, severely fragmented habitat, and ...

'' is a cycad 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 ...

s of the genus '' Wolffia'' are the smallest

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of br ...

s. Fully grown, they measure 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 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, 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 = ...

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

References

{{Reflist, colwidth=30em

External links

Featherwing beetles
on the UF /

IFAS IFAS may refer: * Institute of Food and Agricultural Sciences * Integrated Fixed-Film Activated Sludge, a sewage treatment process * International French adjectival system In rock climbing, mountaineering, and other climbing disciplines, clim ...

Featured Creatures Web site Organism size Biological records es:Tamaño de los seres vivos

Microorganisms

Obligate endosymbiotic bacteria

''Pelagibacter ubique''

''Mycoplasma genitalium''

''Nanoarchaeum''

Eukaryotes (Eukaryota)

Viruses

Animals (Animalia)

Molluscs (Molluska)

Bivalvia

Gastropods (Gastropoda)

Cephalopods (Cephalopoda)

Arthropods (Arthropoda)

Arachnids (Arachnida)

Non-hexapod crustaceans (Crustacea)

Insects (Insecta)

Echinoderms (Echinodermata)

Sea urchins

Starfish

Fish (Pisces)

Amphibians (Amphibia)

Frogs and toads (Anura)

Salamanders, newts and allies (Urodela)

Sauropsids (Sauropsida)

Lizards and snakes (Squamata)

Turtles and tortoises (Testudines)

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)

Plants (Plantae)

Gymnosperms (Gymnospermae)

Angiosperms (Angiospermae)

Dicotyledons

Other

Nanobes

See also

References

External links