tuó names the Chinese alligator (Alligator sinensis), one of only two surviving alligator species in the world. Two compounds:
鼍龙 (literally 'tuó-dragon' - the colloquial Chinese name; in folk tradition the alligator's roar was thought to be a dragon calling rain),
扬子鳄 (Yangtze crocodile - the modern zoological term, more common in everyday usage). The historical compound
鼍鼓 names a drum stretched with alligator hide - Han bronzes show such drums in ritual processions.