Paraliparis mentikoilon, Stein, 2012

Stein, David L., 2012, Snailfishes (Family Liparidae) of the Ross Sea, Antarctica, and Closely Adjacent Waters 3285, Zootaxa 3285, pp. 1-120 : 72-75

Paraliparis mentikoilon n. sp.

Figs. 51, 52

Holotype. NMNZ P.043721, male?, 262 mm TL, 240 mm SL, 71°52.37' S, 174°04.29' E, NW edge of Mawson Bank, R / V Tangaroa, Stn. IPY / CAML TAN 0802 /167, 25 Feb 2008, 1954– 1990 m. NMNZ P.043721/1, cleared and stained right pectoral girdle.

Diagnosis. Chin pores in a clear depression with definite anterior fold. Premaxillary teeth about 30 in outer row, posteriorly uniserial for about 18 teeth, anteriorly forming about 12 irregular oblique rows forming band about three teeth wide; mandibular teeth about 50, uniserial except near symphysis; symphyseal gaps present in both jaws. Gill opening 16% head length. Pectoral fin with 21–22 rays, notch rays rudimentary, girdle with three (2+0+1) round radials. Anus posterior to gill flap and pectoral fin base. Caudal rays seven. Pyloric caeca long, up to about 60% head length.

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FIGURE

Description. Counts. V 71 (13+58), D ~63, A 56, C 7, P 21–22 (14–16+2–3+4), radials 3 (2+0+1), pc 7, pores 2–6?–7–1. Ratios. HL 17.1, HW 13.1, sn 5.3, E 4.2, orbit 5.2, io 7.7, uj 6.8, go 2.7, preD 27.7, preA 44.4, aAf~24 UPL 12.0, LPL 11.6. In % HL: HW 76.3, sn 30.9, E 24.3, orbit 30.4, io 45.0, uj 39.4, go 15.6, preD 161.8, preA 259.4, aAf~140, UPL 70.3, LPL 67.6, cp 2.9, pcl 61.8.

Head short, less than 1/5 SL, low, dorsal profile flat and gradually rising from snout to postorbital region. Snout short, low, bluntly rounded, projecting slightly beyond upper jaw. Nostrils short, tubular, more or less on horizontal through mid-pupil, a short distance anterior to orbit. Mouth horizontal, terminal; lower jaw deep, triangular, slightly included laterally, oral cleft barely reaching to below anterior margin of orbit. Undamaged pores of mandibular series large, chin pores much smaller, about half size of more posterior pores. Chin pores well separated, their distance apart about 3% HL, set in a depression or shallow pit with well defined u-shaped tissue fold anteriorly and possibly a less well defined posterior fold. Teeth simple, sharp, evenly spaced canines, arranged uniserially for more than half of jaw length. Premaxillary teeth posteriorly in a single row of about 18, becoming anteriorly irregularly triserial for another approximately 12 oblique tooth rows forming narrow band about three teeth wide. Mandibular teeth somewhat smaller, uniserial for posterior 40 teeth then another approximately 10 anterior teeth with bi- or tri-serial inner teeth. Symphyseal gaps clearly present in both jaws. Eye prominent with large pupil, orbit diameter about equal to snout, not entering dorsal profile of head, slightly less than 1/3 HL. Gill opening completely above pectoral fin base, not reaching ventrally to upper pectoral fin ray, slightly longer than 15% HL. First arch gill rakers nine. Opercular flap broadly triangular, supported by a shallowly curved crescent opercle, its tip lower than its origin and almost horizontal, barely reaching a point above dorsalmost pectoral fin ray base. Pore formula unknown.

Pectoral fins about 3/4 head length; tip of upper lobe reaching well behind midpoint of abdominal cavity, about 2/3 of distance to anal fin origin. Uppermost ray about even with lower margin of orbit. Upper lobe rounded, of 14– 16 rays, reaching to about 2/3 body cavity length. Notch rays 2–3, the cleared and stained right pectoral girdle has two short filamentous rudimentary rays. Lower lobe long, of four rays, reaching about 2/3 distance towards tip of upper lobe; insertion of lowest ray below opercle and orbit. A clear gap present between lower fin lobes. Pectoral girdle with 3 (2+0+1) radials, moderately large, round; R1 and R2 very close, almost touching; scapular blade with a very narrow slit, R1 and R2 with very narrow dorsal and ventral slits; R1 and R2 equal in size, R4 slightly larger. Scapula with a broad blade and a long, deep helve, a small slit in edge of proximal blade. Coracoid helve moderately long and stout, no ventral notch present at its base.

Body behind head dorsoventrally flattened, probably deepest behind head over mid-abdomen. Dorsal fin insertion between vertebrae 6–7, anal fin insertion between vertebrae 13–14. Dorsal and anal fins distinctly deepest about 2/3 of SL posteriorly. Anus posterior to tip of opercular flap and pectoral base. Peritoneum clearly visible through body wall. Body cavity probably deep, dorsally humped above pectoral fin base. Hypural complex fused, slit absent. Caudal fin of seven (3/4) rays, auxiliary rays absent. Pyloric caeca seven, of various lengths, longest more than 60% HL. SECM probably well developed. Skin thick, strong.

Color of body in alcohol grayish-rose, snout and area around mouth blackish. Black peritoneum visible through body wall. Mouth dusky purplish grey, branchial cavity blackish, stomach and pyloric caeca pale except for extensive black remnants of possible blood vessels on stomach.

Distribution. Known only from a single specimen collected off the northwest edge of Mawson Bank, Ross Sea at 1954–1990 m.

Etymology. The specific epithet mentikoilon , a noun in apposition, from the Latin mentos, chin, and Greek koilon, cavity or hollow, to denote the chin pore pair in a pit.

Comparisons. Most similar to P. neelovi and likely to be incorrectly identified as that species, P. mentikoilon differs clearly in having chin pores in a depression with a clear anterior fold (vs no fold or depression), more caudal fin rays (7 vs 6), slits in R1 and R2 (vs none), a coracoid with a shorter, stouter helve (vs longer and slender), premaxillary teeth uniserial for only slightly more than half of jaw (vs almost all uniserial), fewer mandibular teeth (~50 vs 75–80), anus behind gill flap (vs below gill opening), longer gill opening (~16 vs 10–11% HL), and some other morphometric characters.

Comments. Andriashev (2003:332) mentioned that two of his P. neelovi specimens had a filamentous auxiliary caudal fin ray (e.g., seven rays) but this was displaced forward as usual for such rays. In contrast, all seven rays of the new species are well developed and firmly based on the posterior edge of the hypural plate.