Smallest organisms
The genome of Nasuia deltocephalinicola, a symbiont of the European pest leafhopper, Macrosteles quadripunctulatus, consists of a circular chromosome of 112,031 base pairs.
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.
With a size of approximately 200 to 300 nm, M. genitalium is an ultramicrobacterium, smaller than other small bacteria, including rickettsia and chlamydia.
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.
[6] The Erebor lineage of Microheliella maris is the smallest known heliozoan with an average cell body diameter of 2.56 μm.
[7] Some biologists consider viruses 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.
[12][13] The smallest RNA virus in terms of genome size is phage BZ13 strain T72 at 3,393 nucleotides length.
[citation needed] Several species of Myxozoa (obligately parasitic cnidarians) never grow larger than 20 μm (0.020 mm).
Additional studies and the discovery of further minute frog species are likely to change the rank order of this list.
[66] Parvicursor was initially seen as one of the smallest non-avian dinosaurs known from an adult specimen, at 39 cm (15 in) in length, and 162 g (5.7 oz) in weight.
[69][70] 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).
[77] The Etruscan shrew (Suncus etruscus), is the smallest mammal by mass, weighing about 1.8 g (0.063 oz) on average.
[81][82] 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).
[83] The smallest known member of the rodent order is the Baluchistan pygmy jerboa, with an average body length of 3.8 cm (1.5 in).
[77] The smallest member of the primate order is Madame Berthe's mouse lemur (Microcebus berthae), found in Madagascar,[84] with an average body length of 9.2 cm (3.6 in).
Nanobes, tiny filamental structures first found in some rocks and sediments, were first described in 1996 by Philippa Uwins of the University of Queensland, but it is unclear what they are, and if they are alive.
