Psednos longiventris Stein, 2012, n. sp.

Psednos longiventris n. sp.

Figs. 29, 30

Holotype. NMNZ P. 042033, ripe female, 77 mm SL estimated, 87 mm TL estimated, 42°46.15' S, 175°06.61' E, north central Chatham Rise, R/V Tangaroa, Stn. TAN 0589/077, 5 July 2005, 1054– 1058 m. Poor condition, skinned and broken in half behind abdomen. NMNZ P. 042033 /1, cleared and stained right pectoral girdle.

Diagnosis. Abdomen long, distance from mandible to end of abdominal cavity about 187% HL, angle of mouth 60°, teeth lanceolate, sharp; premaxillary symphyseal gap absent, mandibular symphyseal gap narrow. Coronal pore absent. Pectoral fin rays 16 (7+4+5). Radials 4 (1+1+1+1), R1, R2 notched. Stomach black, intestine creamy white.

Description. Counts: V>45, D na, A na, C 6, P 16, radials 4, gr 7/10, pc 8, pores na. Ratios: % SL na. In % HL: sn 24.9, E 20.3, orbit 25.8, io ~23, uj 36.4, mabd 186.6, pabd 114.7.

Head short, its dorsal profile low, flat, gradually rising to crest of low occipital hump. Owing to strongly oblique mouth, snout noticeably posterior to symphysis of lower jaw and behind that of premaxillae. Nostrils single, about midway between anterodorsal margin of orbit and snout. Eye large, prominent, about 1/5 HL, distinctly below dorsal outline of head. Mouth strongly oblique, about 60°. Teeth in both jaws sharp canines, innermost teeth largest, slender and lanceolate, recurved, pointing posteriorly. Premaxillary teeth in about 32 curved oblique rows of up to about eight teeth each forming a narrow band; posteriormost teeth uniserial.

Mandibular teeth similar, but forming a distinctly wider band and not uniserial posteriorly. Gill opening unknown but dorsal end apparently well above pectoral base. Gill rakers of first arch 7/10, arranged generally in opposition, inner rakers extending much farther ventrally than outer ones. Spinules arranged on each raker in a V shaped patch located on forward side of rakers; a few spinule patches appear to have three rows, but most spinules are in no discernible pattern. Opercular flap damaged, but opercle long, weakly curved, pointed ventrally and somewhat posteriorly. Pore formula unknown, coronal pore absent.

Pectoral fin dorsal ray about on horizontal through posterior corner of mouth. Pectoral fin rays 7+4+5. Upper lobe rays close together, notch rays distinctly more widely spaced, none rudimentary; lower lobe rays close together. Pectoral symphysis below opercular-posttemporal joint, anterior to a vertical through gill opening. Radials 4 (1+1+1+1), R1, R2 notched, R3, R4 round, unnotched; R3 smallest, R4 largest. Interradial fenestrae between scapula and R1, R1–R2. Scapula ventrally hemicircular, rounded with a strong dorsal helve; coracoid poorly calcified and stained.

Trunk unusually long, abdominal cavity clearly longer than deep. Anus position unclear, certainly at anterior of abdominal cavity, probably below gill opening. Vertebrae 11+>34. Dorsal and anal fin origins unknown. Abdomen and internal organs intact, pyloric caeca medial on right side of stomach, plump, digitate. First three neural spines forked distally, remainder single for entire length. Hypural elements fused, no slit, caudal fin rays six (3/3).

In alcohol, skin color unknown, body pale; mouth brown dotted, brownish branchial cavity. Peritoneum brownish black, stomach black, pyloric caeca reticulated black at the base, distally pale. Intestine creamy white.

The specimen has ripe eggs of 2.1 mm diameter.

Distribution. Known from the holotype only, collected on the north central Chatham Rise off New Zealand at 1056 m.

Etymology. The specific epithet longiventris, from the Latin long- and venter, abdomen, to note the particularly distinctive morphological feature of this species, the long abdominal cavity.

Comparisons. Despite its poor condition, this specimen is clearly a previously unknown species: its long abdominal cavity and four radials are distinctive and set it apart from the other known species. With regard to abdomen length only it is most similar to P. cryptocaeca, but differs in its longer mandible to abdomen end length (187 vs 175% HL), upper jaw length (36 vs 46% HL), interorbital width (~23 vs ~42% HL), and mouth angle (60 vs 45°). Discounting the radial number, it differs from all three described Australian species, P. balushkini, P. nataliae, and P. whitleyi, in its shorter snout (25 vs 30–35% HL), narrower interorbital space (~23 vs 40–45% HL), shorter upper jaw (36 vs 49–53% HL), and longer lower jaw (57 vs 44–50% HL).

Comments. Occurrence of four pectoral radials is unusual; all previously examined Psednos species have had three, either in a 2+0+1 or 1+1+1 pattern (Chernova & Stein 2002). The small size of R3 suggests it may be anomalous. Although similar anomalies have not been reported in Psednos, they are not rare in species of other genera (Stein 2012, and others). If R3 is anomalous, the radial formula would be 3 (2+0+1).