Protelytroptera
| Order | Protelytroptera |
| Age | ~290–252 Ma (Permian) |
| Size | ~2–5 cm body length |
| Diet | Likely herbivore or detritivore |
| Fossil Sites | Elmo, Kansas and others |
The Protelytroptera are an extinct order of Permian insects that independently evolved hardened forewings resembling the elytra of modern beetles. Despite this superficial similarity, they were not beetles and represent a separate evolutionary experiment in wing modification.
Description
Protelytropterans had a body plan somewhat similar to modern beetles: the forewings were thickened and hardened (sclerotized), forming protective covers over the membranous hindwings. However, the detailed wing structure differs significantly from true beetle elytra. The hindwings of protelytropterans folded in a distinctive fan-like pattern, and the wing venation was different from that of Coleoptera.
Body sizes ranged from about 2 to 5 cm, and overall body shape was somewhat elongate. The mouthparts were of the chewing type.
Convergent Evolution
The Protelytroptera provide an excellent example of convergent evolution: the independent development of similar structures in unrelated lineages. The hardened forewing is a feature that evolved at least three times in insect history — in protelytropterans, in beetles (Coleoptera), and in earwigs (Dermaptera). In each case, the selective advantage was likely similar: protection of the delicate flight wings from damage in tight habitats such as bark crevices, soil, and leaf litter, and reduction of water loss through the wing surface.
Extinction
Protelytroptera went extinct during or shortly after the Permian-Triassic extinction. They left no descendants. The ecological niches they occupied were eventually filled by true beetles, which diversified enormously during the Triassic and Jurassic periods.