Thysanura is the now

deprecated Deprecation is the discouragement of use of something human-made, such as a term, feature, design, or practice. Typically something is deprecated because it is claimed to be inferior compared to other options available. Something may be deprec ...

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

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

in the

class Class, Classes, 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 d ...

Insecta Insects (from Latin ') are 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 of jointed leg ...

. 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 appearanc ...

and firebrats), share several characteristics, such as of having three long caudal filaments, the lateral ones being the cerci, while the one between (

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

) is a medial cerciform appendage, specifically an epiproct. They are also both wingless, and have bodies covered with fine scales, rather like the scales of the practically unrelated

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

. 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 ...

, 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, including the Zygentoma. 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 is

Apterygota The name Apterygota is sometimes applied to a former Subclass (biology), 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 silverfis ...

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 zoology, zoologist, specialising in arthropods. Having trained as a Roman Catholic priest before the French Revolution, Latreille was imprisoned, and only regained hi ...

, 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 con ...

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

{{Authority control Taxa named by Carl Julius Bernhard Börner Obsolete arthropod taxa