Psednos platyoperculosus, Stein, David L., 2012

Stein, David L., 2012, A Review of the Snailfishes (Liparidae, Scorpaeniformes) of New Zealand, Including Descriptions of a New Genus and Sixteen New Species, Zootaxa 3588, pp. 1-54 : 46-48

Psednos platyoperculosus n. sp.

Figs. 35 , 36

Holotype. NMNZ P. 031315, male, 98 mm SL, 118 mm TL, 42°44.32' S, 177°25.98' W, Chatham Rise, R/V Tangaroa, Stn. TAN 9406/389, 24 July 1994, 1141– 1163 m.

Diagnosis. Vertebrae 59, pectoral fin rays 16–17, caudal fin rays 6, pyloric caeca 7. Body humpbacked. Mouth angle about 40°. Gill opening above pectoral and extending ventrally in front of 1–3 rays, about 1/4 HL. Opercle a broad stout shaft dorsally, widening at level of gill opening and then narrowing to form a sharp posteroventrally pointing tip reaching to behind pectoral fin base. Symphyseal pores small, widely separated, obscure. Abdomen short, ca 80% HL. Body whitish, pyloric caeca reticulated black at base and for about 1/2 length, pale distally.

Description. Counts: V 59, D 49 or 50, A 43 or 44, C 6, P 16–17, radials unknown, gr 10/8, pc 7, pore formula unknown. Ratios: HL 21.9% SL, HW 13.6, sn 5.8, E 5.1, orbit 7.1, io 10.6, uj 8.7, go 5.5, UPL 14.4, LPL 15.3, bd 27.2, preD 28.2, preA 36.3, sna 19.4, ma 19.6, aAf 19.1, mabd 30.5, pabd 17.3. In % HL: HW 61.9, sn 26.5, E. 23.2, orbit 32.6, io 48.4, uj 39.5, go 25.1, UPL 65.6, LPL 69.8, bd 124.2, preD 128.4, preA 165.6, sna 88.4, ma 89.3, aAf 87.0, mabd 139.1, pabd 79.1.

Head short, deep; dorsal profile rising steeply and evenly at an angle of about 50–60° to prominent occipital hump. Snout and symphysis of upper jaw included, tip of mandible most anterior point of body. Snout short, low, about on horizontal with lower margin of orbit. Nostril single, tubular, short, about on horizontal with lower half of pupil. Eye prominent, about 1/5 HL, orbit not entering dorsal profile of head. Mouth oblique, its angle about 40°, symphysis of lower jaw projecting beyond that of upper jaw when mouth closed. Oral cleft short, only reaching below anterior margin of orbit; posterior of maxilla below middle or rear of orbit. Teeth slender, sharp canines, almost no gap at premaxillary symphysis, premaxillary teeth arranged in about 24 oblique rows of up to six teeth each, forming a gradually widening band to symphysis; uniserial only at posteriormost end of band. Mandibular teeth similar to those in upper jaw, but generally larger, especially innermost teeth; a narrow gap present at symphysis. Angle of retroarticular about 90°. Gill opening above pectoral and extending ventrally in front of 1–3 rays, its length about 1/4 HL. Opercle a thick stout shaft dorsally, widening at level of gill opening and then narrowing to form a sharp posteroventrally pointing tip supporting the triangular opercular flap, its tip behind bases of pectoral fin rays. Opercular flap sharply pointed, the tip at about mid point of gill opening, lower margin of tip straight. Gill rakers on first arch 10/8, alternating. Spinules generally arranged in a V, with smallest spinules at apex and a few scattered spinules outside the V. Mid arch rakers with better developed spinule pattern. Pore formula unknown, coronal pore absent, a single suprabranchial pore present. Symphyseal pores small, widely separated, difficult to see.

Pectoral fin dorsal ray slightly higher than posterior corner of upper jaw, about midway between ventral margin of orbit and posterior end of oral cleft. Pectoral fin rays R 7+4+5, L 8+4+5. Upper lobe not quite reaching end of body cavity, notch moderately shallow, about half upper lobe length, rudimentary rays absent; lower lobe reaching about 4/5 distance to end of upper lobe. Lower lobes joined by a skin fold to each other and to abdomen just anterior to anus. Fin rays of upper and lower lobes distinctly more closely spaced than those in notch, free distally for a significant proportion of their length. Pectoral girdle not examined.

Trunk anteriorly deep, tapering evenly and rapidly to caudal. Occipital hump well developed; highest and deepest point of body anterior to gill opening. Vertebral formula 13+46, first four vertebrae forming a very tight dorsal arc manifested by the high, prominent hump. Neural spines of second and third vertebra double. Dorsal fin origin between vertebrae 7–8, anal fin origin between vertebrae 13–14. Anus noticeably posterior to pectoral symphysis by less than 1/4 head length; a stout genital papilla present just posterior to anus. Distance from pectoral symphysis to end of body cavity short, ca 4/5 HL. Pyloric caeca digitate, plump, moderately long. Hypural complex completely fused, no slit evident. Caudal rays 3/3. Skin thin, fragile, transparent white.

Fresh color of body evenly pinkish brown except for black peritoneum and areas where dark branchial cavity shows through head tissue. Color of body in alcohol whitish, head darker owing to visibility of branchial cavity through skin; mouth and tongue brown-spotted, branchial cavity dusky. Peritoneum black, visible through body wall; stomach and intestine blackish brown, caeca reticulated black for proximal half, pale distally.

Distribution. Known only from the East Chatham Rise at midwater depths of about 1150m.

Etymology. The specific epithet platyoperculosus from the Greek platy, broad, and Latin operculum, cover, referring to the unusually wide opercle of this species.

Comparisons. Psednos platyoperculosus is most similar to P. n e m n e z i and to P. chathami . It differs from P. nemnezi in upper jaw length (39 vs 49–52% HL), orbit diameter (33 vs 28–29% HL), distance from pectoral symphysis to abdomen end (79 vs 85–93% HL), and anus to anal fin length (87 vs 93–98% HL). It differs from P.

chathami in number of dorsal and anal fin rays (49–50 vs 53, and 43–44 vs 45–46, respectively), mouth angle (40° vs 30°), interorbital width (48 vs 40% HL), snout length (26 vs 17% HL), anus to anal fin length (87 vs ~98% HL), preanal fin length (166 vs 157% HL), and pectoral symphysis to abdomen end (79 vs 91% HL).

Owing to similarity of proportions, P. platyoperculosus and P. cryptocaeca may be confused, but they differ distinctly in distance from the pectoral symphysis to abdomen end (79 vs 120% HL), greater body depth (124 vs 136% HL), shorter upper jaw (40 vs 46% HL), shorter gill opening (25 vs ~30% HL), anus to anal fin distance (87 vs 116% HL), and preanal fin length (166 vs 191% HL).

Figures

FIGURE 35. Psednos platyoperculosus n. sp. Holotype. NMNZ P. 031315, 98 mm SL. A. lateral view; B. first gill arch; C. spinules on rakers.

FIGURE 36. Psednos platyoperculosus n. sp. Holotype. NMNZ P. 031315, 98 mm SL. Lateral view of fresh specimen. (Photo by A. Stewart, Te Papa)