Key to species of Engyprosopon found in waters around Taiwan

1a. Gill rakers without spinules on their inside edges; ocular-side lower jaw 2.0– 2.5 in HL.............................. 2

1b. Gill rakers with spinules on their inside edges; ocular-side lower jaw 1.5–2.0 in HL................................. 7

2a. Distal half of caudal fin with a pair of large, distinct. blackish blotches........................................... 3

2b. Distal half of caudal fin without blackish blotches............................................................ 5

3a. Gill rakers 0 + 13 (0–6 + 13–18 in comparative specimens)............................................ E. xystrias

3b. Gill rakers 0–3 + 5–11.................................................................................. 4

4a. Body ovate, its depth 1.63–1.86 in SL; ocular-side pectoral-fin rays not filamentous, usually shorter than head length.............................................................................................. E. grandisquama

4b. Body rather elongate, its depth 1.87–2.03 in SL; ocular-side pectoral-fin rays filamentous, longer than head length................................................................................................. E. multisquama

5a. Interorbital width very narrow, its width 7.8–12.5 in HL; scales 50–51 in lateral line; gill rakers 0 + 6–8.......... E. mogkii

5b. Interorbital width very wide, its width 1.7–3.9 in HL; scales 43–48 in lateral line; gill rakers 0–3 + 8–11................ 6

6a. Small eyes placed away from head margin (Fig. 8), upper eye diameter 3.1–4.0 in HL; depth of caudal peduncle 1.8–2.1 in HL; body depth 1.8–2.1 in SL.................................................................. E. maldivense

6b. Large eyes placed near to head margin (Fig. 10), upper eye diameter 2.7–2.9 in HL; depth of caudal peduncle 2.2–2.3 in HL; body depth ~ 1.7 in SL............................................................... E. brevifrontale sp. nov.

7a. Scales 37–40 in lateral line; ocular-side pelvic-fin rays elongate in males, 1.7–1.8 in HL; fin membrane of ocular-side pelvic fin with many black spots in males.............................................................. E. longipelvis

7b. Scales 46–52 in lateral line; ocular-side pelvic-fin rays not elongate in either sex, 1.9–3.0 in HL; fin membrane of ocular-side pelvic fin without many black spots in either sex............................................................. 8

8a. Eyes separated by narrow, concave interorbital space in both sexes; eyes large, upper eye diameter 3.0– 3.5 in HL; anterior teeth on upper jaw not enlarged; blind side of body dark in males.................................. E. mozambiquense

8b. Eyes nearly contiguous, separated by extremely narrow interorbital space, almost filled entirely by a bony ridge in both sexes; eyes small, upper eye diameter 3.8–4.3 in HL; anterior teeth on upper jaw enlarged, canine-like; blind side of body not dark in either sex........................................................................ E. parvipectorale sp. nov.