Thysanurans, the silverfish, are of primitive design, appearing in the Devonian. Thysanura is thought by some to be the linking order between wingless and winged insects. The compound eyes are small; have three tail bristles on the end of their abdomen; the mouthparts are external; some species have scales covering the body. After hatching, the nymphs change to adults with minimal metamorphosis. The young are similar to adults except in size, molting until sexual maturity is attained. Molting may continue into adulthood, and there may be more than forty molts in the life of a thysanuran. There are some 700 named species.

Gallery of Fossil Thysanura Images
Thysanura indet. Cretaceous Crato Formation, Brazil	Fossil Thysanuran in amber that measures 23 mm including the very long centertail.	Silverfish in amber.