Thysanura

Definition

A deprecated ordinal name formerly applied to wingless insects with three caudal filaments (two lateral cerci and a medial epiproct), including silverfishes, firebrats, and jumping bristletails. Once treated as the order Thysanura within subclass Apterygota, the group was recognized as paraphyletic in the late 20th century; its two constituent suborders, Zygentoma (silverfishes and firebrats) and Archaeognatha (jumping bristletails), were subsequently elevated to independent ordinal status. The name persists in older taxonomic literature and some general reference works.

Etymology

From Greek thysanos (bristle) + oura (tail), referring to the three bristle-like tail filaments characteristic of these insects.

Example

In mid-20th-century entomology textbooks, the silverfish Lepisma saccharina was classified in the order Thysanura alongside jumping bristletails; modern works place it in Zygentoma and jumping bristletails in Archaeognatha, reflecting the rejection of Thysanura as a natural group.

Synonyms

• bristletails (informal, calque)

Related Terms

• Zygentoma
• Archaeognatha
• Apterygota
• cercus
• Epiproct
• paraphyly
• Silverfish
• Dicondylia

Usage Notes

Thysanura is now considered an obsolete taxon; current practice treats Zygentoma and Archaeognatha as separate, monophyletic orders. The name may still appear in older literature, museum collections, and some field guides. Specialists avoid Thysanura in formal classification, though it remains useful for historical context when discussing 19th- and 20th-century entomological literature. Not to be confused with the genus-level names Thysanura in other phyla (e.g., certain mites and jellyfish).