Paraliparis orbitalis, Stein, 2012

Stein, David L., 2012, Snailfishes (Family Liparidae) of the Ross Sea, Antarctica, and Closely Adjacent Waters 3285, Zootaxa 3285, pp. 1-120 : 85-90

Paraliparis orbitalis n. sp.

Figs. 61, 62

Holotype. NMNZ P.045678, ripe female, 215 mm TL, 200 mm SL, 71°18.30' S, 172°03.00' E, Off Cape Adare , Antarctica, F/ V Antarctic Chieftain, Stn. OBS 2729/053, 17 January 2009, 1110– 1210 m. NMNZ P.045678/1, cleared and stained right pectoral girdle.

Diagnosis. V 65 (9+56). Lower jaw included. Teeth stout, simple canines forming wide bands anteriorly in both jaws, symphyseal gaps absent. Pectoral fin rays 22–24, caudal 9 (4/5), radials 4 (3+1), scapula and coracoid with well-developed helves. Snout-anus distance 20% (about equal to HL), anus-anal fin 18% SL; snout short ~20% head length, eye 33, orbit 38% HL. Black pigment on body visible under, above and below pale gill flap.

Description. Counts. V 65 (9+56), D 57, A 51, C 9, P 22–24 (17–19+2+3), radials 4 (3+1), pc ≥6, pore formula unknown. Ratios. HL 20.8, HW 12.1, sn 4.2, E 7.0, orbit 7.9, io 7.5, uj 6.8, go 2.5, bd ~21, preD 23.6, preA 36.6, sna 20.0, ma 15.9, aAf 17.7, UPL 14.8, LPL 12.0, pabd 25.6. In % HL: HW 58.1, sn 20.5, E 33.5, orbit 38.1, io 30.1, uj 36.1, go 22.9, bd ~103, preD 114.0, preA 176.4, sna 96.6, ma 76.6, aAf 85.3, UPL 71.1, LPL 57.8, pabd 123.6, cp 2.6.

Head short, shallower than body, dorsal profile rising steeply through flat interorbital region. Snout short, bluntly rounded, not projecting much beyond upper jaw. Nostrils tiny, difficult to find, immediately anterior to orbit, on a horizontal through lower half of pupil. Anterior ends of suborbitals protruding as blunt knobs (possibly an artifact of preservation). Mouth horizontal, inferior; lower jaw included, oral cleft reaching below anterior of pupil. Teeth simple, blunt, stout, well-spaced canines, forming wide bands near symphysis, on premaxillary arranged in about 7–8 oblique rows of up to about 13 teeth; mandibular teeth similar to those of premaxilla but possibly a little smaller and one or two more rows present. Viewed from front of head, anterior tooth bands visible with mouth slightly open. Symphyseal gaps absent in both jaws. Eye prominent; orbit unusually large with a cartilaginous thickened rim entering dorsal profile of head, distinctly more than 1/3 HL. Gill opening above pectoral fin base and extending ventrally over about 6 rays to below orbit but well above oral cleft; its length less than1/4 head. Opercular flap well developed, supported by dorsally curved opercle, its tip almost horizontal and reaching distinctly behind pectoral fin base. Blackish lining of branchial cavity extending on body beyond gill opening, visible both above and below margin of opercular flap. Pore formula unknown. Chin pores paired, with thickened rims, smaller than remaining mandibular pores but not tiny; distance between them slightly greater than their diameter.

Pectoral fin shorter than head, longest ray of upper lobe reaching behind midpoint of abdominal cavity but not to its end; barely reaching or not quite reaching anal fin origin. Uppermost ray on horizontal below lower margin of orbit but above mouth. Upper lobe rounded, of 22–24 rays, notch rays two, not rudimentary, notch moderately shallow. Lower lobe short, of three (1+2) rays, the uppermost ray distinctly more distant from the next lower ray than that ray is to the ventralmost; insertion of lowest ray below rear of orbit and eye, reaching not much farther posteriorly than upper lobe base. No obvious gap present between lower pectoral fin lobes. Right pectoral girdle with 4 (3+1) large, unnotched closely spaced radials, upper three radials of similar size, R1 and R2 round, R3 rounded but irregular, R4 smaller and almost square. Top two radials almost touching. Scapula double headed, its blade larger, but helve also very well developed; coracoid with a moderately long strong helve, basal notch absent.

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61 FIGURE

Body laterally flattened, deepest behind head. Dorsal fin insertion between vertebrae 4–5, anal fin insertion between vertebrae 10–11. Dorsal and anal fins not abruptly deeper at any point. Anus between lower pectoral fin lobe rays, below gill opening. Peritoneum clearly visible through body wall, abdominal cavity relatively short. Hypural complex fused, slit absent. Caudal fin of nine (4/5) rays, auxiliary rays absent. Pyloric caeca of various lengths from short to moderately long, fat, digitate. SECM apparently not well developed. Skin thin, easily damaged.

Color of body unknown; remaining skin on anterior white, remainder on tail increasingly purplish posteriorly. Mouth purplish, most teeth brown, branchial cavity dark brown, peritoneum black, stomach and pyloric caeca pale.

The holotype has eggs up to about 4 mm diameter.

Distribution. Known only from the type, collected at 1110–1210 m off Cape Adare, Ross Sea, Antarctica.

Etymology. The specific epithet orbitalis from the large prominent orbits and eyes that dominate the front of the head.

Comparisons. This species is most similar to P. magnoculus in its large orbits and pectoral fin ray counts (owing to damage, dorsal, anal and vertebral counts are unavailable for P. magnoculus ). However, P. orbitalis differs distinctly in its more posterior anus position (sna 97 vs 65–67% HL; anus below opercular flap vs below posterior of orbit) and consequently shorter distance from anus to anal fin (85 vs 113% HL), the more dorsal position of the pectoral fin (about even with lower margin of orbit vs even with corner of mouth), lack of symphyseal tooth gaps (vs wide, present in both jaws), position of anteriormost lower lobe ray (below rear of orbit vs below midorbit) and other characters. It is similar in general counts and proportions to P. somovi from the South Shetland Islands, but differs in having more vertebrae (65 vs 60–63 counted from 30 specimens), lower pectoral fin lobe of three (vs four) rays, anal fin insertion more posterior (between vertebrae 10–11 vs 8–9), a shorter snout (20 vs 27– 35% HL), shorter gill opening (23 vs 27–33% HL), and other characters. It could be confused with P. fuscolingua , which also has large eyes, but differs in having larger eyes (7 vs 4–6% SL; 34 vs 22–30% HL), and shorter dorsal and anal fins (57 vs 61–63 and 51 vs 54–57 rays). Paraliparis trunovi Andriashev 1986 also has relatively large eyes (25–29% HL), but differs in having only two radials, completely black color, eight caudal rays, rudimentary pectoral notch rays, and many other characters. The new species is also very similar to P. diploprora from

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Paraliparis

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FIGURE

2600 m in the Scotia Sea in pectoral fin structure, pectoral ray number and position, but differs in number of vertebrae (65 vs 60), length of gill opening (23 vs 36–38% HL, in front of 6 vs 7–10 rays), and absence of the two soft snout protuberances.