Key to seven Callogobius species of the Red Sea

(To be used for specimens at least 15 mm SL. Counts of scales in lateral series can vary by ± 2 depending on the user or the condition of the specimen)

1a. Chin with 4 transverse mandibular papillae rows (Row 16) on each side; temporal canal present with 2 pores (K’, L’) above operculum; scales in lateral series 21–25, usually 24; in intact adult specimens, anterior first dorsal-fin spines free of membranes for about one-quarter or more of spine length.......................... Callogobius pilosimentum n. sp. (Fig. 2)

1b. Chin with more than 10 transverse mandibular papillae rows (Row 16) on each side (the rows extending posteriorly to the lower edge of the preoperculum); temporal canal absent (no pores above operculum); scales in lateral series 22–41, more than 24 in most species; in intact adult specimens, anterior first dorsal-fin spines free of membranes for less than one-quarter spine length.............................................................................................. 2

2a. Pelvic fin united and frenum weak to moderately well-developed; preopercular row (Row 20) continuous with transverse opercular papillae row (Row 21)............................................................................. 3

2b. Pelvic fins separate or partially united and frenum weak or absent; preopercular papillae row (Row 20) not continuous with transverse opercular row (Row 21)....................................................................... 4

3a. Head with strongly contrasting markings including bars radiating from eye, body with dark bars and horizontal stripes; D VI + I,10; A I,8.................................................................... Callogobius amikami (Fig. 3)

3b. Head, body and fins mostly dark with narrow dark horizontal stripes on body, dark vertical bars usually not obvious; D VI + I,9; A I,7........................................................................ Callogobius dori (Fig. 5)

4a. Scales in lateral series 33–41........................................................................... 5

4b. Scales in lateral series 22–32............................................................................ 6

5a. Head pores absent; scales mostly cycloid, except for a few on caudal peduncle; pelvic fins united about two-thirds of length of medial rays, frenum weak......................................................... Callogobius clarki (Fig. 4)

5b. Head pores present; scales ctenoid on posterior half of body; pelvic fins separate or with a minute membrane, frenum absent......................................................................... Callogobius flavobrunneus (Fig. 6)

6a. Scales in lateral series 27–32; pelvic fins separate or with a minute basal membrane........ Callogobius sclateri (Fig. 7A)

6b. Scales in lateral series 22–25; pelvic fins united about two-thirds of the length of pelvic fin.... Callogobius sp. A (Fig. 7 B)