question: What may have replaced the `` hind wing '' as the primary mode of aerial maneuverability ?
answer: fully mobile fan of tail feathers
turker_answer: A fully mobile fan of tail feathers may have replaced the `` hind wing '' as the primary mode of aerial maneuverability .
rule-based: Fully mobile fan of tail feathers may have replaced the `` hind wing '' as the primary mode of aerial maneuverability .