Key to the species of Lepadichthys

1a. Dorsal-fin rays 14–17; anal-fin rays 11–15.................................................................. 2

1b. Dorsal-fin rays 9–13; anal-fin rays 8–11....................................................................6

2a. Dorsal and anal fins not joined to caudal fin; pectoral-fin rays 23; head not broad, head width 6.5 in SL; two oblique bluish white lines on postorbital head; top of snout with a broad white stripe...................... .. L. bilineatus n. sp. (Oman)

2b. Both dorsal and anal fins, or dorsal fin only, joined to caudal fin; pectoral-fin rays 26–28; head moderately broad, head width 4.7–6.2 in SL; color not as above......................................................................... 3

3a. Dorsal-fin rays 14; dorsal fin only joined to caudal fin; 6 gill rakers on second gill arch............................................................................................... L. ctenion Briggs & Link (NW Indian Ocean)

3b. Dorsal-fin rays 15–17; both dorsal and anal fins joined to caudal fin; 8–14 gill rakers on second gill arch................ 4

4a. Disc medium, its length 4.9–5.8 in SL; 10–14 gill rakers on second gill arch................ L. frenatus Waite (W. Pacific)

4b. Disc moderately small, its length 6.0– 7.6 in SL; 8–9 gill rakers on second gill arch.................................. 5

5a. Upper attachment of gill membrane opposite 4th to 7th pectoral-fin ray; head width 4.6–5.0 in SL; postdorsal-caudal distance 3.4–3.8 in dorsal-fin length............................................... L. sandaracatus Whitley (W. Australia)

5b. Upper attachment of gill membrane opposite 9th pectoral-fin ray; head width 5.2–6.2 in SL; postdorsal-caudal distance 6.4–7.3 in dorsal-fin length...................................................... L. erythraeus Briggs & Link (Red Sea)

6a. Pectoral-fin rays 16–17; disc very small, its length 9.0 in SL; head and body white with two longitudinal dark red stripes.......................................................................... L. akiko Allen & Erdmann (W. Papua)

6b. Pectoral-fin rays 25–30; disc length 4.0– 8.2 in SL; color not as above............................................ 7

7a. Upper attachment of gill membrane opposite 7th to 9th pectoral-fin ray........................................... 8

7b. Upper attachment of gill membrane opposite 10th to 15th pectoral-fin ray........................................ 10

8a. Dorsal and anal fins confluent with caudal fin; postdorsal-caudal distance 4.0– 4.5 in dorsal-fin length; disc length 4.0– 5.3 in SL........................................................................ L. springeri Briggs (Philippines)

8b. Dorsal and anal fins not joined to caudal fin; postdorsal-caudal distance 1.3–2.8 in dorsal-fin length; disc length 5.4–6.0 in SL.................................................................................................... 9

9a. Postdorsal-caudal distance 2.7–2.8 in dorsal-fin length; 11–16 gill rakers on second gill arch............................................................................................. L. coccinotaenia Regan (W. Indian Ocean)

9b. Postdorsal-caudal distance 1.3–1.8 in dorsal-fin length; 8 gill rakers on second gill arch.. L. caritus Briggs (W. Indian Ocean)

10a. Dorsal-fin rays 12; anal-fin rays 10; disc length 8.2 in SL.......................... L. bolini Briggs (Indo-West Pacific)

10b. Dorsal-fin rays 9–11; anal-fin rays 8–9; disc length 5.1–5.7 in SL.............................................. 11

11a. Anus much closer to anal-fin origin than to rear margin of disc; disc length 5.5–5.7 in SL; 8 sharp gill rakers on second gill arch........................................................ L. lineatus Briggs (Red Sea and Indo-West Pacific)

11b. Anus about halfway between anal-fin origin and rear margin of disc; disc length 5.1–5.3 in SL; 5 shallow gill rakers on second gill arch....................................................................... L. minor Briggs (W. Pacific)