Which extinct order is distinguished by winglets on the prothorax?

• A. Ephemeroptera.
• B. Odonata.
• C. Lepidoptera.
• D. Palaeodictyoptera.

Answer: (B)

Wing arrangement and thoracic structure reveal how ancient insects experimented with flight. In some extinct Paleozoic lineages, there were small wing-like projections actually on the first thoracic segment, the prothorax. This feature—the presence of winglets on the prothorax—is a distinctive trait used to identify the extinct order Palaeodictyoptera. It sets them apart from other groups listed, whose wings arise on the middle and hind thoracic segments and do not display prothoracic winglets in the same way. Ephemeroptera and Lepidoptera have their wings on the mesothorax and metathorax with different patterns, and Odonata’s wings are likewise tied to the middle and hind segments without prothoracic winglets. Thus, the prothorax winglets point to Palaeodictyoptera as the extinct order described.