What evidence shows that bristletails are among the oldest known insects?

Evidence that bristletails (order Archaeognatha) are among the oldest known insects is provided by the discovery of a significant fossil specimen in Gaspé Bay, Quebec, Canada.1

This fossil, which retains important structural details such as fragments of the head and thorax, is estimated to be approximately 390 to 392 million years old, dating back to the Devonian Period. As primitive, wingless insects, bristletails are classified as apterygotes, a group that represents some of the earliest lineages of the class Insecta.12