Pomacentrus aurifrons, Gerald R. Allen, 2004

Gerald R. Allen, 2004, Pomacentrus aurifrons, a new species of damselfish (Pomacentridae) from Melanesia., Zootaxa 399, pp. 1-7 : 3-7

Pomacentrus aurifrons , new species

(Figures 1-2; Table 1)

Holotype: WAM P.32261-001, 61.5 mm SL, Toiyama Island, Amphlett Group, Milne Bay Province, Papua New Guinea (9°18.909’S, 150°51.100’E), 12 m, spear, G.R. Allen, 1 June 2000.

Paratypes: AMS I.42620-001, 2, 48.5-57.0 mm SL, collected with holotype ; WAM P.27827-038, 2, 22.4-42.0 mm SL, Hayne Harbour, Los Negros Island, Manus, Papua New Guinea (approximately 2°03’S, 147°26’E), 7-9 m, rotenone, G. Allen & R. Knight, 6 October 1982 ; WAM P.29742-001, 2, 49.4-49.6 mm SL, Nagada Harbour, Madang, Papua New Guinea (approximately 5°14’S, 145°45’E), S. Poss et al., 1 May 1987 ; WAM P.32261-002, 5, 44.9-53.5 mm SL, collected with holotype .

Diagnosis. Dorsal rays XIII,12; anal rays II,13; pectoral rays 16-17; tubed lateral-line scales 14-17; gill rakers 6-7 + 12-15 (total 19-22); body depth 1.9-2.1 in SL; pale grey to nearly white with blue spot on head scales, vertically elongate, blue streak on most body scales, broad zone of yellow encompassing snout, forehead, and base of anterior dorsal spines, translucent fins with bluish dorsal, anal, and caudal soft rays, and narrow yellow margin on spinous dorsal fin.

Description. Dorsal rays XIII,12; anal rays II,13; all dorsal and anal soft rays branched, the last to base; pectoral rays 17(16-17), the upper and lowermost 2 unbranched; pelvic rays I,5; principal caudal rays 15, the median 13 branched; upper and lower procurrent caudal rays 4, the posterior pair segmented; scales in longitudinal series 28; tubed lateral-line scales of holotype 15 on left side and 16 on right (14-17); posterior midlateral scales with a pore or deep pit (in continuous series) 8 (8-9); scales above lateral line to base of middle dorsal spine 1.5; scales below lateral line to origin of anal fin 9; gill rakers 7 + 13 (6-7 + 12-15), total rakers 20 (19-22).

Body ovate, the depth 2.1 (1.9-2.0) in SL, and compressed, the width 2.3 (2.5-2.8) in body depth; HL 3.4 (3.2-3.4) in SL; dorsal and ventral profile of head evenly rounded from dorsal and pelvic fin origins to snout; snout shorter than orbit, its length 3.8 (4.0-4.5) in HL; orbit diameter 3.2 (3.0-3.7) in HL; interorbital space convex, its width 2.9 (2.8- 3.2) in HL; caudal-peduncle depth 2.0 (1.9-2.2) in HL; caudal-peduncle length 2.3 (1.8- 2.4) in HL.

Mouth terminal, small, and oblique, forming an angle of about 40° to horizontal axis of head and body; maxilla reaching vertical at anterior edge of pupil, the upper-jaw length 3.2 (3.1-3.8) in HL; teeth biserial, at least at front of jaws, consisting of outer row of larger incisiform to conical teeth and slender buttress teeth behind and in spaces between outer row teeth, 35 (35-42) in outer row of upper jaw and 35 (32-40) in outer row of lower jaw. Tongue triangular with rounded tip, papillose on dorsal surface. Gill rakers long and slender, the longest on lower limb near angle about two-thirds length of longest gill filaments. Nostril (no posterior nostril detected) round with slightly raised rim, directly anterior to middle of eye and about midway between anterior edge of eye and upper lip.

Opercle ending posteriorly in a flat spine, the tip acute but short, barely projecting from beneath a large scale; preopercle serrations poorly developed, 13 on left side of holotype (5-13); preorbital with a small spine posteriorly and separated by a notch (poorly developed in 2 paratypes) from suborbital series; lower edge of suborbital smooth.

Scales finely ctenoid; head scaled except lips, tip of snout, preorbital, and suborbital; a scaly sheath at base of dorsal and anal fins, averaging about one-half pupil width at base of spinous portion of dorsal fin and slightly less at base of anal fin; a column of scales on each membrane of dorsal and anal fins, narrowing distally, those on spinous portion of dorsal fin progressively longer, reaching about two-thirds distance to spine tips at end of spinous dorsal and beginning of soft dorsal, then gradually shorter on remainder of fin; small scales on caudal fin extending about two-thirds to three-fourths distance to posterior margin; small scales on basal one-fourth of pectoral fins; a cluster of several scales forming median process, extending posteriorly from between base of pelvic fins, its length slightly more than half that of pelvic spine; axillary scale above base of pelvic spine about one-half length of pelvic fin.

Origin of dorsal fin over first or second lateral-line scale; predorsal distance 2.8 (2.6- 2.9) in SL; preanal distance 1.6 (1.5-1.6) in SL; prepelvic distance 2.6 (2.4-2.8) in SL; base of soft portion of dorsal fin contained about 1.8 times in base of spinous portion; dorsal-fin spines gradually increasing in length to last spine; first dorsal spine 4.7 (3.9-4.4) in HL; seventh dorsal spine 2.1 (1.9-2.1) in HL; last dorsal spine 1.7 (1.6-2.0) in HL; membranes of spinous portion of dorsal fin incised; fifth or sixth dorsal soft ray longest, 1.4 (1.2-1.5) in HL; first anal spine 5.7 (4.1-52) in HL; second anal spine 1.6 (1.6-1.8) in HL; longest (ninth) anal soft ray 1.5 (1.3-1.5) in HL; fourth pectoral ray longest, 1.0 (1.0-1.1) in HL; pelvic-fin spine 2.0 (1.8-2.0) in HL; pelvic- fin length 1.2 (1.1-1.2) in HL; caudal fin emarginate with rounded lobes, its length 0.9 (0.8) in HL; caudal concavity 4.4 (3.3- 4.8) in HL.

Colour in alcohol: generally uniform brown except slightly lighter on breast, and lips tan; fins tan with paler margin on dorsal fin and small dark brown spot at base of four uppermost pectoral fin rays.

Colour when alive (from underwater photographs): pale grey to nearly white with blue spot on head scales, vertically elongate, blue streak on most body scales, broad zone of yellow encompassing snout, forehead, and base of anterior dorsal spines, translucent fins with bluish dorsal, anal, and caudal soft rays, and narrow yellow margin on spinous dorsal fin.

Comparisons. Pomacentrus aurifrons is most similar to P. smithi Fowler and Bean 1928 (Figure 3) from Indonesia and the Philippines. The two species are especially similar with regards to meristic features and colouration. However, P. aurifrons is distinguished by its taller dorsal fin, with the longest soft ray averaging 1.37 in HL (n = 10), compared to 1.65 in HL for P. smithi (n = 9). Although subtle, there are also consistent colour pattern features. The ground colour of P. aurifrons tends to be light grey, nearly whitish, compared to the pale greenish hue of P. smithi . In addition, P. smithi lacks the bright yellow area on the snout, forehead, and dorsal fin base that is characteristic of P. aurifrons . Furthermore, P. smithi frequently has 3-4 rows of blue spots on the side of the caudal peduncle, and these markings often persist as pale horizontal lines in preserved specimens. A final difference is related to the male nuptial coloration of P. smithi , which is characterised by diagonal dark bands on the head and enhanced dark scale markings (see middle photograph on page 158 in Allen, 1991). Although nuptial behaviour was observed for P. aurifrons on several occasions there was no noticeable change in colour.

Pomacentrus aurifrons and P. smithi are apparently geminate species, most likely evolved from a common ancestral population that was fragmented as a result of sea level fluctuations during past glacial periods (Allen, 1972; Randall,1998). Randall (1998) listed 52 additional geminate pairs from the East Indian region, which provides a convincing argument for this hypothesis.

Distribution and habitat. Pomacentrus aurifrons is currently known from Papua New Guinea, Solomon Islands, and Vanuatu (the latter two areas are based on sight records by the author). It is replaced by the closely related P. smithi at Indonesia, Sabah (Malaysian Borneo), and the Philippines.

Pomacentrus aurifrons is relatively common on coastal fringing reefs and offshore platform reefs at depths between 2-14 m. The substrate generally consists of mixed sponge, soft corals, and branching hard corals. This fish is usually seen in groups that swim a short distance above the coral, apparently feeding on zooplankton.

Etymology. This species is named Pomacentrus aurifons from the Latin auri- (gold) and frons (forehead) in reference to the characteristic yellow marking on the forehead.