Porogadus solomonensis, Schwarzhans & Møller, 2021

Schwarzhans, Werner W. & Møller, Peter R., 2021, Revision of the ‘ dragon-head’ cusk eels of the genus Porogadus (Teleostei: Ophidiidae), with description of eight new species and one new genus, Zootaxa 5029 (1), pp. 1-96 : 54-57

Porogadus solomonensis n. sp.

Figs. 4 , 25–26 , 45 , 50 , Tab. 1–7

Porogadus sp : Nielsen & Møller 2007: 33, fig. 18.

Material examined ( 3 specimens): Holotype ZMUC P771579 , 175 + mm SL, Galathea 3 expedition, R / V Vaedderen, sta. 061219-05, collected by Jørgen G. Nielsen and Tammes Menne, Solomon Sea, 13°45’S 156°41’E, 2255- 2283 m, 19 Dec. 2006; paratypes ZMUC P771578 , 173 + mm SL and ZMUC P 771581, 175 mm SL, same data as holotype.

Diagnosis. Precaudal vertebrae 17–18; long gill rakers on first gill arch 16–17; HL:HD 1.71–1.79; relatively few and moderately strong head spines: on ethmoidal, interorbital, supraorbital, sphenotic, supratemporal, inner and outer posttemporal; weak lacrimal ridge; absent on prefrontal, along inner and outer preopercular rim and 5th infraorbital; opercular spine weak, flat; maxilla without scales; small opercular flap; lower lateral line pores until beginning of anal fin 19; basibranchial tooth patches consisting of single median and pair of small lateral patches; vomer with broad dentition patch with 4 rows of teeth; palatines with broad dentition patch (5–7 rows of teeth); otolith with single colliculum; OL:OH = 1.42–1.60; OL:TCL = 2.24–2.34.

Description. Meristics: precaudal vertebrae 17 (17–18), 2 (1–2) last vertebrae without ribs; pectoral-fin rays 18 (17–18); D/V = 7 (6–7); D/A = 23 (23–27); V/A = 18 (18–19); long gill rakers on lower first gill arch 17 (16–17). Gill rakers in the holotype on lower first gill arch with seven short rakers, followed by a series of 17 long rakers. The lower seven of those intercept by small plate shaped rakers. The long rakers are blade shaped and armed with spinules on the inner rim. Upper gill arch with a series of five semi long rakers and five plate like rakers intercept- ed.

Morphometrics: in % of SL: HL 16.2 (15.3–16.2); maximal HD 9.0 (8.9–9.1); HD through center of eye 6.3 (5.9–6.3); bony interorbital width 3.6 (3.1–3.6); snout length 5.0 (4.7–5.4); upper jaw length 9.8 (9.0–9.8); predorsal 18.2 (17.2–18.2); preanal 30.0 (29.6–30.0); prepelvic 13.5 (12.3–13.5); prepectoral 16.6 (15.6–16.6); pectoral length no measurable. Relations: HL:HD = 1.79 (1.71–1.79); HL to snout length 3.21 (2.81–3.33); preanal to predorsal 1.65 (1.65–1.72); predorsal to prepectoral 1.09 (1.09–1.13).

Slender fish with long tapering tail and moderately long snout. Maximal size of fishes investigated 175 mm SL. Head moderately long and moderately slender, with flat dorsal profile, with few strong spines and ridges as follows: ethmoidal (1), interorbital (1), supraorbital (1), sphenotic (2), supratemporal (2), inner and outer posttemporal (2–3); weak lacrimal ridge; no spines on prefrontal, along inner and outer preopercular rims and on 5th infraorbital. Opercle with weak, flat spine. Eye small, located in strongly asymmetric orbit. Maxilla extending far beyond eye, strongly widened posteriorly and with distinct supramaxilla. Infra-/postorbital and mandibular-preopercular pores wide, head top with cavernous system extending from prefrontal to between occiput and sphenotic and supraorbital spines and on occiput in front of nape with up to 5 bilateral symmetrical openings (pores or damaged thin skin cover?). Head squamation on opercle, and cheeks, absent on maxilla, occiput, frontal, and around eyes. Opercle with three moderately sized neuromasts behind preopercular edge; opercular flap small. Lateral line rows rarely well visible and therefore number of pores countable only in rare instances. Lower lateral line row with 19 pores until beginning of anal fin in one specimen.

Dentition. All teeth tiny and cone-shaped. Vomer with a short dentition patch with 4 rows of teeth anteriorly, naked or with few teeth posteriorly; palatines with a broad dentition patch with 5–7 rows of teeth in middle part. Premaxilla tooth patches not fused anteriorly; ca. 7 teeth rows anteriorly and 1–2 rows posteriorly. Dentary tooth patches narrow, not fused anteriorly; ca. 4 teeth rows anteriorly and a single row posteriorly. Basibranchial tooth patches consisting of single, long median and pair of small lateral patches

Otolith morphology (n = 3). Size up to 3.3 mm in length (holotype 2.8 mm); OL:OH = 1.42–1.60; OH:OT = 2.7–2.9. Relatively thin and moderately elongate otoliths with irregular, subtriangular shape, anteriorly and posteriorly inferiorly rounded, posteriorly slightly expanded. Dorsal rim with broad, rounded pre- to mediodorsal angle, ventral rim shallow, nearly flat. All rims smooth, somewhat irregular. Inner face nearly flat, smooth, with short, centrally positioned sulcus; OL:TCL = 2.24–2.34. Sulcus shallow, undivided, with broad and shallow colliculum, but somewhat narrowed posteriorly. Dorsal field with large indistinct depression; ventral field smooth, with faint ventral furrow anteriorly joining ventral rim of otolith below anterior part of sulcus. Outer face smooth, with mild, anteriorly positioned umbo.

Coloration. Fresh dead color with light brown body and dark, almost black head and opercle, but head top lighter; belly dusty grey. Color of preserved specimens similar, but darkness of head and opercle somewhat faded.

Discussion. Porogadus solomonensis is the only species with a regularly occurring pair of basibranchial tooth patches in addition to the long central patch. It differs from other members of the Porogadus trichiurus group also in the low number of long gill rakers on the first gill arch (16–17 vs 18–21), the high predorsal length (17.2–18.2 vs 13.7–16.3, rarely 17.0), and the broad tooth patches on vomer and palatines.

Distribution. Porogadus solomonensis is only known from the type locality in the Solomon Sea, where it occurs at moderate depth between 2255–2283 m and about 350 km off the shelf break.

Etymology. Named after the type location, the Solomon Sea.

Figures

FIGURE 4. Examples of first gill arches. 4A, Porogadus miles ZMUC P2397157, 259 mm SL. 4B, Tenuicephalus multitrabs n. sp. CAS 83066, 156 mm SL. 3C, P. solomonensis ZMUC P771578, 173+ mm SL.

FIGURE 25. Porogadus solomonensis n. sp.; 25A–B, ZMUC P771579, holotype, 175+ mm SL, 13°45’S, 156°41’E, 2255– 2283 m; 25C, ZMUC P771578, paratype, 173+ mm SL, 13°45’S, 156°41’E, 2255–2283 m.

FIGURE 26. Porogadus solomonensis n. sp.; 26A–B, ZMUC P771579, holotype, 175+ mm SL, 13°45’S, 156°41’E, 2255– 2283 m, head drawings; 26C–D, ZMUC P771578, paratype, 173+ mm SL, 13°45’S, 156°41’E, 2255–2283 m, otolith (C inner face, D ventral view); 26E–F, ZMUC P771579, holotype, 175+ mm SL, 13°45’S, 156°41’E, 2255–2283 m, otolith (E inner face, F ventral view); 26G, ZMUC P771581, 175 mm SL, paratype, 13°45’S, 156°41’E, 2255–2283 m, otolith (inner face).

FIGURE 45. Geographic distribution of the species of the Porogadus trichiurus group.

FIGURE 50. Depth versus distance from shelf plots for specimens of the Porogadus trichiurus group (upper panel) and the Porogadus catena group (lower panel).