yuán names the giant soft-shelled turtle, the largest freshwater turtle native to China. The classical Mozi list
鱼鳖鼋鼍 ('fish, soft-shell turtle, giant soft-shell, alligator') pairs it with
鼍 (Yangtze alligator) as the iconic large reptile of southern Chinese waters. Compounds:
鼋鼍 (the pair, named together in classical texts),
癞头鼋 ('pock-headed yuan' — a folk name). Now critically endangered; only a handful of individuals remain alive worldwide.