The oldest fossils definitively recognized as hexapods belong to which group?

• A. Collembola
• B. Diplura
• C. Protura
• D. Thysanura

Answer: (A)

The question tests when we first can place a hexapod in the fossil record with confidence. The oldest fossils that are unmistakably hexapods belong to Collembola, the springtails. A famous early specimen shows six legs and, crucially, the mouthparts tucked inside the head—a hallmark of Collembola rather than the later-winged insects or other hexapod groups. Because these preserved features align with Collembola and allow a definite placement within Hexapoda, they mark the earliest known hexapod lineage with solid fossil support. The other groups—Diplura, Protura, and the true insects—either lack such ancient, well-defined fossils or do not display the distinctive early-character set to the same degree, so they aren’t identified as the oldest hexapod lineage.