Monura is an extinct order of wingless insects in the subclass Apterygota

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...

. They resembled their modern relatives, the bristletail

Archaeognatha

Archaeognatha is an order of wingless insects, also known as jumping bristletails. They are among the least evolutionarily changed insects, appearing in the Devonian period along with the arachnids. The name Archaeognatha is derived from Greek Archaeos meaning "ancient" and gnatha meaning "jaw"...

s, and had a single lengthy filament projecting from the end of the abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

. They also had a pair of leg-like cerci

Cercus

Cerci are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans. Cerci often serve as sensory organs, but they may also be used as weapons or copulation aids, or they may simply be vestigial structures.Typical cerci may appear to be...

and some non-ambulatory abdominal appendages. The largest specimens reached 30 millimetres (1.2 in) or more, not counting the length of the filament.