Smallest organisms

The genome of Nanoarchaeum equitans is 491 Kbp nucleotides long.^{[citation needed]}

Pelagibacter ubique

Nanoarchaeum

microbe 200 to 500 nm (0.00020 to 0.00050 mm) in diameter. It was discovered in 2002 in a hydrothermal vent off the coast of Iceland by Karl Stetter. A thermophile that grows in near-boiling temperatures, Nanoarchaeum appears to be an obligatory symbiont on the archaeon Ignicoccus; it must be in contact with the host organism to survive. Guinness World Records recognizes Nanoarchaeum equitans as the smallest living organism.^{[citation needed}

]

Eukaryotes (Eukaryota)

algae of the genus Ostreococcus are the smallest free-living eukaryote. The single cell of an Ostreococcus measures 800 nm (0.00080 mm) across.^{[citation needed}

]

Viruses

Some

genetic material and can employ the metabolism of their host, they can be considered organisms. Also, an emerging concept that is gaining traction among some virologists is that of the virocell, in which the actual phenotype of a virus is the infected cell, and the virus particle (or virion) is merely a reproductive or dispersal stage, much like pollen or a spore.^[4]

The smallest viruses in terms of genome size are single-stranded DNA (

Phi-X174 with a genome size of 5,386 nucleotides.^[5] However, some ssDNA viruses can be even smaller. For example, Porcine circovirus type 1 has a genome of 1,759 nucleotides^[6] and a capsid diameter of 17 nm (1.7×10⁻⁵ mm).^[7] As a whole, the viral family geminiviridae is about 30 nm (3.0×10⁻⁵ mm) in length. However, the two capsids making up the virus are fused; divided, the capsids would be 15 nm (1.5×10⁻⁵ mm) in length. Other environmentally characterized ssDNA viruses such as CRESS DNA viruses, among others, can have genomes that are considerably less than 2,000 nucleotides.^[8][9]

The smallest

ribozymes, satelliviruses and viroids.^{[citation needed}

]

Animals (Animalia)

Several species of

cnidarians) never grow larger than 20 μm (0.020 mm).^[12] One of the smallest species (Myxobolus shekel) is no more than 8.5 μm (0.0085 mm) when fully grown, making it the smallest known animal.^[13]

Molluscs (Molluska)

Bivalvia

The shell of the nut clam Condylonucula maya grows 0.54 mm (0.021 in) long.^[14]

Gastropods (Gastropoda)

The smallest water snail (of all snails) is Ammonicera minortalis in North America, originally described from Cuba. It measures 0.32 to 0.46 mm (0.013 to 0.018 in).^[15][16]

The smallest land snail is Acmella nana. Discovered in Borneo, and described in November 2015, it measures 0.7 mm (0.028 in).^[17] The previous record was that of Angustopila dominikae from China, which was reported in September 2015. This snail measures 0.86 mm (0.034 in).^[18]

Cephalopods (Cephalopoda)

Further information: Cephalopod size

Maximites was the smallest known ammonoid. Adult specimens reached only 10 mm (0.39 in) in shell diameter.^[19]

Arthropods (Arthropoda)

The smallest arthropods are

Stygotantulus stocki, with a length of 94 micrometres (0.0037 in).^[21]

Arachnids (Arachnida)

• There is a debate about which spider is smallest. According to Guinness World Records, "Two contenders are from the Symphytognathidae genus Patu: males of Patu digua described in Colombia had a body length of 0.37 millimetres (0.015 inches), while the Samoan moss spider (P. marplesi) could be as small as 0.4 millimetres (0.016 inches) long."^[22] 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 0.43 mm (0.017 in) and 0.48 mm (0.019 in) respectively.^[22] Males of both species are potentially smaller than the females, but no Anapistula ataecina or Anapistula caecula have been measured yet.^[22]
• Cochlodispus minimus is the smallest mite. An adult individual measured with a body length of 79 μm (0.079 mm).^[23] However, PBS claims "The tiniest mite on record is 82 microns long" but does not name a species.^[24]

Insects (Insecta)

• Adult males of the parasitic wasp Dicopomorpha echmepterygis can be as small as 139 μm (0.139 mm) long, smaller than some species of protozoa (single-cell creatures); females are 40% larger.^[25] Megaphragma caribea from Guadeloupe, measuring 170 μm (0.17 mm) long, is another contender for smallest known insect in the world.
• Scydosella musawasensis at 325 μm (0.325 mm) long; a few other nanosellines are reportedly smaller, in historical literature, but none of these records have been confirmed using accurate modern tools. These are among the tiniest non-parasitic insects.^[26]

• The
  butterflies in the world, with a wingspan of about 1 cm (0.39 in).^[27]

The smallest sea cucumber, and also the smallest echinoderm, is Psammothuria ganapati, a synaptid that lives between sand grains on the coast of India. Its maximum length is 4 mm (0.16 in).^{[28] [29]}

Sea urchins

The smallest sea urchin, Echinocyamus scaber, has a test 6 mm (0.24 in) across.^[29]

Starfish

• One of the smallest
  standard length.^[30] 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
  anal fin ray further forward, under dorsal fin
  4.
• Male individuals of the
  Photocorynus spiniceps have been documented to be 6.2–7.3 mm (0.24–0.29 in) 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 50.5 mm (1.99 in).^{[33][34][35][36]}

The smallest vertebrates (and smallest amphibians) known are Paedophryne amauensis frogs from Papua New Guinea, which range in length from 7.0–8.0 mm (0.28–0.31 in), and average 7.7 mm (0.30 in).^[37][38] Other very small frogs include:

• Brachycephalus didactylus
  from Brazil (reported as 9.6–9.8 mm (0.38–0.39 in))
• several species of
  E. limbatus (8.5–12 mm (0.33–0.47 in)) and Eleutherodactylus orientalis
  (12.5 mm (0.49 in)) from Cuba,
• Gardiner's Frog
  Sechellophryne gardineri
  from the Seychelles (up to 11 mm (0.43 in)),
• several species of Stumpffia such as S. tridactyla (8.6–12 mm (0.34–0.47 in)) and S. pygmaea (males 10–12.5 mm (0.39–0.49 in); females: 11 mm (0.43 in)) and Wakea madinika (males: 11–13 mm (0.43–0.51 in); females: 15–16 mm (0.59–0.63 in)) from Madagascar.

Paedophryne swiftorum (body length 8.5 mm (0.33 in)) is not included in the smallest vertebrates known with other nine species of frogs.^[39] The two species Microhyla borneensis (males: 10.6–13 mm (0.42–0.51 in); females: 16–19 mm (0.63–0.75 in))^[40][41] and Arthroleptella rugosa (males: 11.9–14.1 mm (0.47–0.56 in); females: 15.5 mm (0.61 in)) were once the smallest known frogs from the Old World. In general these extremely small frogs occur in tropical forest and montane environments. There is relatively little data on size variation among individuals, growth from metamorphosis to adulthood or size variation among populations in these species. Additional studies and the discovery of further minute frog species are likely to change the rank order of this list.

Salamanders, newts and allies (Urodela)

The average snout-to-vent length (SVL) of several specimens of the salamander Thorius arboreus was 17 mm (0.67 in).^{[citation needed]}

Sauropsids (Sauropsida)

Lizards and snakes (Squamata)

• The
  B. tuberculata)^[45] and 15–16 mm (0.59–0.63 in) for male B. micra,^[46] though females are larger. In 2021, a new species of Brookesia, B. nana, was discovered, with a snout-vent length of 13.5 mm (0.53 in), possibly making it the smallest known reptile.^[47][48]

• One of the smallest known
  Common blind snake (Indotyphlops braminus) measures 5.1–10.2 cm (2–4 in) long, occasionally up to 15 cm (6 in) long.^[49][50]

Archosaurs (Archosauria)[note 1]

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 1.6 m (5.2 ft) in length.^[52]
• Some extinct
  crocodylomorphs were even smaller.^[53] Fully grown Bernissartia from the Early Cretaceous reached a bit more than 60 cm (24 in) in length.^[54]
• The Early Cretaceous terrestrial notosuchian Malawisuchus was no more than 60 cm (24 in) long.^[55] Other small notosuchians include Anatosuchus at 70 cm (28 in)^[56] and herbivorous Simosuchus at 75 cm (30 in).^[57]

Pterosaurs (Pterosauria)

Nemicolopterus was the smallest pterosaur, it reached about 25 cm (9.8 in) in wingspan.^[58]

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

• With a mass of approximately 1.95 grams (0.069 oz) and a length of 5.5 centimetres (2.2 inches), the
  body mass
  and drinks eight times its total body mass each day. Its nest is 3 cm (1.2 in) across.
• The smallest
  Nettapus). African species reaches the average weight of about 285 grams (10.1 oz) for males and 260 grams (9.2 oz) for females and wingspans between 142 millimetres (5.6 in) and 165 millimetres (6.5 in).^[65] The second smallest waterfowl is the extinct Mioquerquedula from the Miocene.^[66]
• The smallest penguin species is the little blue penguin (Eudyptula minor), which stands around 30–33 cm (12–13 in) tall and weighs 1.2–1.3 kg (2.6–2.9 lb).^[67]
• The smallest bird of prey is the Black-thighed falconet (Microhierax fringillarius), with a wingspan of 27–32 centimetres (11–13 in), roughly the size of a sparrow.^[68]

Non-mammalian synapsids (Synapsida)

The smallest Mesozoic mammaliaform was Hadrocodium with a skull of 1.5 cm (0.59 in) in length and a body mass of 2 g (0.071 oz).^[69]

Mammals (Mammalia)

Marsupials (Marsupialia)

The smallest

The Etruscan shrew (Suncus etruscus), is the smallest mammal by mass, weighing about 1.8 g (0.063 oz) on average.^[71] The smallest mammal that ever lived, the shrew-like Batodonoides vanhouteni, weighed 1.3 grams (0.046 oz).^[72]

Bats (Chiroptera)

The Kitti's hog-nosed bat (Craseonycteris thonglongyai), also known as the bumblebee bat, from Thailand and Myanmar^[73] is the smallest mammal, at 29–33 millimetres (1.1–1.3 in) in length and 2 grams (0.071 oz) in weight.^[74][75]

Carnivorans (Carnivora)

The smallest member of the order Carnivora is the least weasel (Mustela nivalis), with an average body length of 114–260 mm (4.5–10.2 in). It weighs between 29.5–250 g (1.04–8.82 oz) with females being lighter.^{[citation needed]}

Rodents (Rodentia)

The smallest known member of the rodent order is the Baluchistan pygmy jerboa, with an average body length of 4.4 cm (1.7 in).^[70]

Primates (Primates)

The smallest member of the primate order is Madame Berthe's mouse lemur (Microcebus berthae), found in Madagascar,^[76] with an average body length of 9.2 cm (3.6 in).

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 135 cm (53 in); the females are slightly longer, averaging about 141 cm (56 in) in length.^{[citation needed]}

Plants (Plantae)

Gymnosperms (Gymnospermae)

Zamia pygmaea is a cycad found in Cuba, and the smallest known gymnosperm.^[77] It grows to a height of 25 cm (10 in).^[78]

Angiosperms (Angiospermae)

Nanobes are thought by some scientists to be the smallest known organisms,^[81] about one tenth the size of the smallest known bacteria. Nanobes, tiny filamental structures first found in some

• Largest organisms
• Largest prehistoric organisms

Notes