Thysanura is the now

deprecated In several fields, especially computing, deprecation is the discouragement of use of some terminology, feature, design, or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing ...

name of what was, for over a century, recognised as an order in the

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

Insecta Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs o ...

. The two constituent groups within the former order, the

Archaeognatha The Archaeognatha are an order of apterygotes, known by various common names such as jumping bristletails. Among extant insect taxa they are some of the most evolutionarily primitive; they appeared in the Middle Devonian period at about the sa ...

(jumping bristletails) and the

Zygentoma Zygentoma are an order in the class Insecta, and consist of about 550 known species. The Zygentoma include the so-called silverfish or fishmoths, and the firebrats. A conspicuous feature of the order are the three long caudal filaments. The t ...

(

silverfish The silverfish (''Lepisma saccharinum'') is a species of small, primitive, wingless insect in the order Zygentoma (formerly Thysanura). Its common name derives from the insect's silvery light grey colour, combined with the fish-like appearance ...

and

firebrat The firebrat (''Thermobia domestica'') is a small hexapod (typically 1–1.5 cm), in the order Zygentoma. Habitat Firebrats prefer higher temperatures and require some humidity, and can be found in bakeries and near boilers or f ...

s), share several characteristics, such as of having three long

caudal filament Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insec ...

s, the lateral ones being the cerci, while the one between (

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...

) is a medial cerciform appendage, specifically an

epiproct This glossary of entomology describes terms used in the formal study of insect species by entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though ...

. They are also both wingless, and have bodies covered with fine scales, rather like the scales of the practically unrelated

Lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

. In the late 20th century, it was recognized that the two suborders were not

sister taxa In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

, therefore Thysanura was paraphyletic, and the two suborders were each raised to the status of an independent monophyletic order, with Archaeognatha sister taxon to the

Dicondylia The Dicondylia are a taxonomic group (taxon) that includes all insects except the jumping bristletails (Archaeognatha). Dicondylia have a mandible attached with two hinges to the head capsule (dicondyl), in contrast to a hypothetical ancestral m ...

, including the Zygentoma. Fancy Bristletail - Flickr - treegrow (2)

Although the group Thysanura is no longer recognized, the name still appears in some published material. Another name used to separate the two groups from

winged insects The Pterygota ( grc, πτερυγωτός, pterugōtós, winged) are a subclass of insects that includes the winged insects. It also includes insect orders that are secondarily wingless (that is, insect groups whose ancestors once had wings b ...

Apterygota The name Apterygota is sometimes applied to a subclass of small, agile insects, distinguished from other insects by their lack of wings in the present and in their evolutionary history; notable examples are the silverfish, the firebrat, and the ...

Etymology

The name Thysanura, first applied to the group by

Pierre André Latreille Pierre André Latreille (; 29 November 1762 – 6 February 1833) was a French zoologist, specialising in arthropods. Having trained as a Roman Catholic priest before the French Revolution, Latreille was imprisoned, and only regained his freedom ...

, was derived from the Greek θυσάνος, ''thysanos'' for ''fringe'', ''tassel'', ''bristle'' and οὐρά, ''oura'' for "tail", a reference to the three fanned out caudal filaments. This etymology is consistent with the English word "bristletail", which is the

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

for several hexapod species, not all of which fell within Thysanura.

References

* * Charles A. Triplehorn and Norman F. Johnson, ''Borror and DeLong's Introduction to the Study of Insects'', 7th edition (Thomas Brooks/Cole, 2005), pp. 177–180 * ''Firefly Encyclopedia of Insects and Spiders'', edited by Christopher O'Toole, , 2002

External links

Thysanura
– Tree of Life Web Project

{{Taxonbar, from=Q226951 Taxa named by Carl Julius Bernhard Börner Obsolete arthropod taxa