Seleniolycus pectoralis, Peter R. Møller & Andrew L. Stewart, 2006

Peter R. Møller & Andrew L. Stewart, 2006, Two new species of eelpouts (Teleostei, Zoarcidae) of the genus Seleniolycus from the Ross Dependency, Antarctica., Zootaxa 1376, pp. 53-67 : 58-60

Seleniolycus pectoralis sp. nov.

(Figs. 2, 3b, 4).

Materials. Holotype: NMNZ P.40591, 380 mm SL, male, Pacific-Antarctic Ridge, north of Balleny and Scott Islands (64°40.0' to 64°42.3'S, 176°32.0' to 176°44.6'E), depth 1948-2594 m, longline, FV Avro Chieftain, Gerald Anderson, stn. OBS 1742/067, 27 March 2003.

Paratypes: (n = 3): NMNZ P.40595 (2 specimens), 315 mm SL, male, and +350 mm SL (tip of tail missing), female, same data as for holotype ; NMNZ P.42283, 380 mm SL, female, Pacific-Antarctic Ridge (63°39'S, 173°04'E), depth 2267 m, longline, FV San Aotea II, Simon Beatson, stn. OBS 1430/231R, 9 May 2001 .

Diagnosis. Differs from congeners by having ventralmost pectoral fin rays exserted, scales present on posterior 2/5 of body, dorsal fin rays 76-80, and anal fin rays 64-66. It is further diagnosed by the following combination of characters: suborbital head pores 6-7, preoperculomandibular pores 8; predorsal length 28.0-30.7% SL; snout length 28.3-36.6% HL, eye diameter 9.4-12.0% HL; pectoral fin rays 14-16; anterior dorsal fin pterygiophore associated with vertebra 6-7; vertebrae 23-27 + 61-63 = 86-89.

Description. Principal counts and measurements are presented in Table 1. Vertebral centra symmetrical, with prezygapophyses and postzygapophyses of equal horizontal length. Anal fin pterygiophores 3 (3-4), inserted anterior to haemal spine of first caudal vertebra. Caudal fin with 1 epural, 4 upper and 5 lower hypural rays. Epipleural ribs on 3 (3-4) to penultimate precaudal vertebra. Gill rakers on outer surface of first gill arch simple (not furcate) and with spinules. Branchiostegal rays 6. Pectoral fin wedge-shaped; its origin below body midline; lower rays thickened, exserted. Pelvic fin absent.

Body elongate; trunk relatively robust, tail laterally compressed. Head ovoid, robust; anterior profile of snout almost vertical. Eyes relatively large, circular, not reaching dorsal profile of head. Mouth subterminal; lower lips without lateral lobe, upper lip continuous across snout. Snout blunt, upper jaw slightly longer than lower jaw, reaching past middle of eye. Nasal tube well developed, but not reaching upper lip. Gill slit large, extending ventrally to level of lower pectoral fin base or just below. Opercular lobe at dorsal margin of gill slit, angular and relatively prominent.

Jaw, vomer and palatine teeth small and conical. Premaxilla with 3 (2-3) rows. Dentary with 4 (3-4) rows of teeth anteriorly, blending into two rows posteriorly. Vomerine teeth in 4 (3-5) rows. Palatine teeth in 3 (3-4) rows.

Head pores moderate in size; minor variation in numbers observed. Postorbital pores 2 (2-3), located at positions 1, 4 and sometimes 3 (sensu Gosztonyi, 1977); nasal pores 2, one set anteromesial to nasal tube, the other posteromesially; suborbital pores 7 (6-7); preoperculomandibular pores 8, 4 arising from dentary, 1 from anguloarticular and 3 from preopercle; occipital and interorbital pores absent.

Main body lateral line mediolateral, complete to tail tip. Short dorsolateral branch extending from above opercular lobe to near origin of dorsal fin; predorsal branch with widely separated neuromasts extending from above opercular lobe to near caudal fin.

Head and anterior body naked; posterior ca. 40%, covered with small cycloid scales. Dorsal and anal fins naked anteriorly, posteriorly 1/4 scaled, caudal fin naked.

Colour. Body and head in preserved specimens light to medium brown, with darker dorsal and anal fin margins, pectoral fin and nasal tubes (Fig. 2). Peritoneum dark brown, orobranchial chamber and gill rakers pale.

Sexual dimorphism. The few specimens available are insufficient for analyses of sexual dimorphism.

Reproduction. None of the specimens are ripening.

Etymology. Name refers to the pectoral fin morphology, with ventral rays thickened and exserted, a unique character in the genus.

Distribution and habitat. Currently known from only four specimens, caught at two positions along the Pacific-Antarctic Ridge (64°42.3'S, 176°44.6'E and 63°39'S, 173°04'E), at depths of 1948-2594 m (Fig. 4).

Comparison with congeners. Seleniolycus pectoralis is very similar to S. robertsi in having scales on the posterior part of the body (vs. absent in S. laevifasciatus ), a relatively long predorsal distance (28.0-30.7 and 27.1-36.4% SL vs. 20.0-23.8% SL in S. laevifasciatus ), and in the number of suborbital head pores (6-7 and 6 vs. 5 in S. laevifasciatus ). Seleniolycus pectoralis differs, however, from both S. robertsi and S. laevifasciatus by the wedge-shaped pectoral fin, with exserted lower rays (vs. with no exserted rays) (Fig. 3), and in the more robust head and body which is expressed in several morphometric characters (Table 1). Seleniolycus pectoralis further differs from S. robertsi in having a longer pre-scaled distance (58.7-61.8% SL vs. 48.9-55.4% SL) and a larger head (19.8-24.6% SL vs. 16.1-18.8% SL).