Key to species of the genus Zenarchopterus from Taiwan

1A. Snout length slightly longer than width, with only 9 anal-fin rays.................... Zenarchopterus takaoensis sp. nov.

1B. Snout wider than length, with 10–12 anal-fin rays............................................................ 2

2A. Prominent dark stripe on middle snout and extending posteriorly to interorbital; 4–5 th dorsal-fin rays without elongated flap on tip and 6 th anal-fin ray not elongated in adult male.................................................... Z. buffonis

2B. Prominent dark stripe on snout absent; 4–5 th dorsal-fin rays with elongated flap on tip and 6 th anal-fin ray elongated and expended in adult male................................................................................. 3

3A. Only the 6 th anal-fin ray elongated in adult male, the length extending to caudal-fin base..................... Z. duncheri

3B. Both 6 th and 7 th anal-fin rays elongated in adult male, the length extending over caudal-fin base................. Z. dispar