Crossorhombus, Regan, 1920

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 177

Key to species of Crossorhombus in Taiwan

1A. Pectoral fin shorter than HL; caudal fin with two dark bands at base and distal margin; males with pyriform dark blue blotch on blind side, its anterior margin away from dorsal margin of bodyq........................................ C. azureus

1B. Pectoral fin filamentous, longer than HL; dark bands on posterior part of caudal fin or not; males with dark blue blotch on blind side, its anterior margin close to dorsal and ventral margins of body............................................. 2

2A. Black margins on dorsal and anal fins; uppermost and lowermost 3 caudal-fin rays unbranched; anterior margin of blotch on blind side of males smooth or slightly notched..................................................... C. kobensis

2B. No black margins on dorsal and anal fins; uppermost and lowermost 2 caudal-fin rays unbranched; anterior margin of blotch on blind side of males deeply notched, V-shaped............................................................... 3

3A. Caudal fin with a dark band on posterior part; pectoral fin on ocular side filamentous, its length 32.6–41.9% SL in males.......................................................................................... C. valderostratus

3B. Caudal fin without any dark band; pectoral fin on ocular side not elongate, its length 27.8–31.8% SL.......... C. howensis