Key to species of Chascanopsetta in Taiwan

1A. Tip of lower jaw reaching slightly beyond tip of upper jaw, lower-jaw length 19.6–20.1% SL, upper-jaw length 14.5–17.6% SL; vert. 17+38–40=55–57.............................................................. Chascanopsetta lugubris

1B. Tip of lower jaw reaching extremely far beyond tip of upper jaw, lower-jaw length 20.9–25.2% SL, upper-jaw length 16.7– 20.3% SL; vert.17–18+41–43=59–60................................................. Chascanopsetta prognatha