Epigonus draco Okamoto, 2015

Okamoto, Makoto, 2016, Validity of Epigonus megalops (Perciformes: Epigonidae), Redescription of E. atherinoides, and First Record of E. draco from the Central South Pacific, Species Diversity 21, pp. 177-186 : 184

Epigonus draco Okamoto, 2015

[English name: Dragon Deepwater Cardinalfish] ( Figs 3 , 6; Tables 1–2)

Epigonus draco Okamoto, 2015: 121 , fig. 1 [original description, type locality: Solomon Islands (07°43′34″S, 158°29′24″E; 08°41′16″S, 157°41′27″E), western South Pacific ] .

Epigonus ctenolepis (not of Mochizuki and Shirakihara, 1983): Iwamoto and McCosker 2014: 291, fig. 122 (between Luzon and Mindoro, Philippines).

Material examined. 2 specimens, 87.1–104.7 mm SL. Society Islands : MNHN 2014-0217 , 104.7 mm SL, 16°41′11″S, 151°25′30″W, Raiatea island, 638–700 m depth, 16 October 2009; MNHN 2014-0871 , 87.1 mm SL, 16°46′31″S, 151°22′41″W, Raiatea island, 573–611 m depth, 18 October 2009 .

Other material examined. 6 specimens 88.8–160.1mm SL. Solomon Islands: MNHN 2006-0589 , holotype, 127.4 mm SL, 07°43′34″S, 158°29′24″E, 391–623 m depth, 25 October 2004; MNHN 2006-0684 , paratype, 88.8 mm SL, same data as holotype; MNHN 2006-0063 , 2 paratypes, 110.0–145.0mm SL, 08°41′16″S, 157°41′27″E, 786 m depth, 5 November 2004 . Philippines: CAS 235796 , paratype, 160.1 mm SL, 13°36′7″N, 120°23′2″E, between Luzon and Mindoro, 541–636 m depth, 1 June 2011 . Vanuatu: MNHN 2012-0836 , paratype, 128.1 mm SL, 15°41′31″S, 167°01′19″E, west of Malo Island , 481 m depth, 17 September 2006 .

Diagnosis. A species of Epigonus with the following combination of characters: dorsal-fin rays VII-I, 10; pectoral-fin rays 19–20; total gill rakers 22–23; pyloric caeca 7–10; pored lateral-line scales 47–49+3–4; scales below lateral line 9; vertebrae 10 + 15; opercular spine present; maxillary mustache-like processes absent; ribs absent on last abdominal vertebra; uppermost margin of pectoral-fin base lower than horizontal line through center of eye; proximal radial of first anal-fin pterygiophore slender; and mouth cavity black.

Distribution ( Fig. 3 ). Known from the Philippines, Solomon Islands, Vanuatu ( Okamoto 2015), and Society Islands (present study), at depths of 391– 786 m.

Remarks. Epigonus draco was originally described on the basis of six specimens collected from the Philippines, Solomon Islands, and Vanuatu in the western Pacific ( Okamoto 2015). The present specimens represent the first record of this species from the Society Islands ( Fig. 6). These distributional records are located between 15°N and 20°S at depths greater than 390 m; this species is distributed on continental slopes in the western and central tropical Pacific ( Fig. 3 ).

Epigonus draco , E. atherinoides , and E. megalops belong to the E. constanciae group because of having a pungent opercular spine; they are all distributed in the Western Pacific ( Mochizuki and Shirakihara 1983; Okamoto 2015; present study, Fig. 3 ). All three species are similar in having a small number of gill rakers ( Table 2) and lacking ribs on the last abdominal vertebra, but E. draco differs in having the uppermost margin of the pectoral-fin base lower than a horizontal line through the center of the eye (vs. subequal to the center of the eye, Fig. 5A ) and lacking a pair of maxillary mustache-like processes (vs. blunt maxillary mustache-like processes present, Fig. 2 ).

The present specimens match the morphological description given by Okamoto (2015), and their meristic and morphometric features are similar to those of the type specimens ( Table 1). The counts of pyloric caeca are slightly different (9–10 herein vs. 7–9 in the type series), but well within the typical range of meristic variation in the genus (see Okamoto and Motomura 2013: table 2; Okamoto 2015: table 3). These minor differences are considered as intraspecific variation.

Comparative material. Epigonus angustifrons: SNFR 15936, 242 mm SL, SNFR 15937, 205 mm SL, SNFR 15939, 233 mm SL, SNFR 15940, 223 mm SL, SNFR 15943, 210 mm SL, SNFR 15944, 226 mm SL, 33°55′00˝S, 55°20′00˝E, southwestern Indian Ocean, 550–614 m depth, 13 November 2009. Epigonus macrops: BSKU 16702, 150.8 mm SL, BSKU 16703, 128.6 mm SL, 09°27.0′S, 127°58.6′E – 09°28.5′S, 127°56.1′E, Timor Sea , 610–690 m depth, 18–19 June 1972; CAS 234746 , 121.0 mm SL, 09°54.09′S, 12°44.47′E, off Angola, southeastern Atlantic Ocean, 620–630 m depth, 10 March 2007 . Epigonus telescopus: SNFR 16711, 635 mm SL, SNFR 16712, 706 mm SL, 37°25′00˝S, 50°27′00˝E, southwestern Indian Ocean , 661–690 m depth, 11 May 2010 . Epigonus sp. : MNHN 2014- 1583, 117.3 mm SL, 12°52.28′S, 48°07.41′E, Madagascar, 558–592 m depth, 25 June 2009 . Other examined material of Epigonus was listed in Okamoto (2011, 2012, 2015) and Okamoto and Fukui (2011).

Figures

Fig. 3. Distributional records of Epigonus megalops (open stars), E. atherinoides (open circles = previous studies; solid circles = present study), and E. draco (open triangles = previous studies; solid triangles = present study).

Fig. 5. Position of uppermost margin of pectoral-fin base in two similar species. A: E. megalops, USNM 147374, paratype, 116.0mm SL; B: E.ctenolepis, FUMT-P 1567, holotype, 98.0mm SL.

Fig. 2. Dorsal view of snout of Epigonus megalops, USNM 70255, holotype, 125.3mm SL (arrows point to maxillary mustache-like processes).