Pseudoscopelus paxtoni, Melo, Marcelo R. S., 2019

Melo, Marcelo R. S., 2019, A revision of the genus Pseudoscopelus Lütken (Chiasmodontidae: Acanthomorphata) with descriptions of three new species 2710, Zootaxa 2710 (1), pp. 1-78 : 42-44

Pseudoscopelus paxtoni , new species

Figures 16 B , 17 B , 18 A , 19 A–B , 28 H; Table 6.

Holotype. NMNZ P. 28657, 205.1 mm, West Pacific, New Zealand, off the Chatham Islands, at East Chatham Rise , 42º39’ S, 176º57’ W, 1409 m, 13–VII–1992, R / V Tangaroa .

Paratypes. 14 specimens. Pacific , West Pacific: NMNZ P. 18068, 1, 157.5 mm, 44º44’ S, 172º50’ E, 979–1010 m, 22– VIII –1984, R / V James Cook; NMNZ P. 20235, 1, 145.0 mm, 39º28’ S, 178º25’ E, 17– VIII – 1986, R / V James Cook; NMNZ P. 20236, 1, 147.4 mm, 39º21’ S, 178º27’ E, 836– 836 m, 17– VIII –1986, R / V

James Cook; NMNZ P. 21272, 1, 82.8 mm, 39º59’ S, 167º54’ E, 954–957 m, 18– VI –1987, F/ V Explorer; NMNZ P. 24155, 1, 227.9 mm, 44º47’ S, 175º29’ E, 979–1063, 6–XI–1986 , F/ V Arrow; NMNZ P. 24161, 1, 126.8 mm, collected with NMNZ P. 24155; NMNZ P. 24255, 1, 129.2 mm, 40º15’ S, 168º23’ E, 925 m, 16– VII–1989 , F/ V Explorer; NMNZ P. 25805, 1, 158.5 mm, 40º02’ S, 167º58’ E, 893–964 m, 9–VII–1990 , F/ V Will Watch; NMNZ P. 25806, 1, 203.0 mm, collected with NMNZ P. 25805; NMNZ P. 36790, 1, 196.9 mm, 42º35’ S, 173º23’ W, 1223 m, col. unknown ; NMNZ P. 37858, 1, 200.4 mm, 48º18’ S, 170º06’ E, 896 m, 15– X–2000 , R / V Tangaroa ; NMNZ P. 38679, 1, 234.2 mm, 42°48’ S, 179°47.33’ E, 1031 m, 27– VI –2002, R / V Tangaroa ; SIO 07-164 (former NMNZ P. 28793), 1, 213.2 mm, 44º40’ S, 177º33’ W, 1183 m, 3–XI–1991 , R / V Tangaroa ; USNM 391143 (former NMNZ P. 28700), 1, 227.2 mm, 42º41’ S, 179º43’ W, 1288 m, 19–VII– 1992 , R / V Tangaroa .

Non-type (tentative identification). Pacific, West Pacific: NMV A. 6008, 1, 52.2 mm, 38º01’ S, 150º14’ E, 20–XI–1981 , R / V Soela.

Diagnosis. A species of the Pseudoscopelus altipinnis species group, which can be distinguished from P. altipinnis by dentition and photophore pattern: innermost teeth of mesial rows of premaxilla and dentary elongate, when mouth is closed and premaxilla is retracted reach the medial border of the contralateral premaxilla (vs. innermost teeth of mesial rows of premaxilla not extremely elongated, when mouth is closed and premaxilla is retracted teeth do not reach the medial border of premaxilla of the other side); teeth of mesial row of premaxilla and internalmost row of dentary straight (vs. teeth of mesial row of premaxilla and internalmost row of dentary slightly curved); mesial series of premaxillary teeth arranged in transverse rows of one to three rows of teeth (vs. mesial series of premaxillary teeth arranged in transverse rows of one to five rows of teeth).

Description. Large-sized species of Pseudoscopelus , largest specimen examined 234.0 mm SL. Morphometric data summarized in Table 6. General body shape as described for genus with diagnostic characteristics of species and species group.

First dorsal-fin rays viii (3), ix (5*), x (1); second dorsal-fin rays i+22 (1), ii+22 (1), ii+23 (2), ii+24 (5*); anal-fin rays iii+21 (2), iii+22 (2), iii+23 (5*); pectoral-fin rays 11 (1), 12 (4*), 13 (4); pelvic-fin rays I+5 (9*); caudal-fin rays i+7+8+i (8), i+8+7+i (1*). Branchiostegal rays 7 (9*). Pre-caudal vertebrae 17 (2), 18 (3); total vertebrae 36 (1), 37 (2), 38 (2).

Lateral line complete; lateral-line pores 79 (1), 80 (1), 81 (5*), 82 (2). Pores in temporal canal 2 (9); supratemporal canal 2 (1), 3 (8*); otic canal 3 (9*); supraorbital canal 5 (2), 6 (7*); supranasal pore 3 (1), 2 (8*); epiphyseal branch 2 (8*), 3 (1); infraorbital canal 13 (1), 12 (8*); preopercular canal 5 (9*); mandibular canal 6 (9*); fifth pore of mandibular canal 1 (7), 2 (8*).

Dentition. Enlarged teeth on premaxilla, dentary and palatine. Premaxilla and dentary illustrated in Figure 16 B .

Premaxilla moderately wide, widest point of premaxillary body 15–20 % in premaxillary length. Premaxillary teeth on head, neck, body and caudal process. Lateral series of teeth in single longitudinal row, along lateral edge of premaxillary head, neck, body and caudal process; teeth slightly curved.

Premaxillary teeth on head, neck, body and caudal process. Lateral series of teeth in single longitudinal row, along lateral edge of premaxillary head, neck, body and caudal process; teeth slightly curved; posterior four to five teeth on caudal process considerable thicker than anterior, type 1. Canine and fang on ventral shelf of premaxillary head. Middle and mesial series on ventral shelf of premaxillary body. Middle series in two, irregular, longitudinal rows; teeth needle-like, straight, gradually increasing in size from lateral to medial. Mesial series in transverse rows, each row with one to three teeth; teeth needle-like, extremely elongated, reaching contralateral premaxilla, slightly curved, gradually increasing in size from medial to mesial.

Dentary teeth in lateral and mesial series. Lateral series along lateral shelf of dentary, in single, longitudinal row, extending from symphysis to posterior tip; teeth conical, slightly curved. Mesial series on dorsal shelf of dentary, in transverse rows of one to four teeth; teeth straight, needle-like, increasing in size from lateral to mesial. Palatine teeth 4 (2), 5 (3*), 6 (3), 7 (1); in single, longitudinal row.

Teeth on infrapharyngobranchials and fifth ceratobranchial, conical, curved. Teeth on second basibranchial 4 (2), 5 (3*), 6 (3), 7 (1), conical, in single, irregular row. Teeth absent on basihyal and other basibranchials. Gill rakers on first epibranchial 0 (9*); first ceratobranchial 8 (1), 10 (2), 11 (1), 14 (1*), 15 (2), 18 (1), 22 (1); first hypobranchial 1 (1), 2 (1), 4 (1), 6 (1), 8 (2*), 10 (1), 12 (2). Gill rakers absent on other elements.

Luminescent organs. Luminescent organs present as discrete photophores on head and body ( Fig. 17 B ). Photophores on head: dnf, inof 1–2, lpf, opf, ppf and pof absent; mxf elongated, in single irregular row with widely spaced photophores, parallel to maxilla, from below mid-eye, connected to apf posteriorly; apf in angle between dentary and preopercle; vnf in triangular patch posterior to anteriormost supraorbital pore; amf in two to three rows medial to around third pore of mandibular canal; pmf in one to three rows, lateral to mandibular canal, from posterior to fourth pore to halfway between fifth and sixth pores.

Photophores on body: lvf, rtf, scf, spf and svf absent; pf in single row along ventral-most pectoral-fin ray; paf continuous with pf, at pectoral-fin axil; vf in single row, along mesial pelvic-fin ray; vaf triangular, continuous vf and trf, not extending over base of pelvic rays three to five; if in one irregular to two rows, from isthmus to ventral edge of cleithrum, prvf in one irregular to two rows, at anterior portion of pelvic girdle; ptvf in two rows, from posterior half of pelvic fin to close to anus; trf in single irregular row with widely spaced photophores; saf in single row, heart-shaped, extending anteriorly to level of anus, and not connected posteriorly, not extending further to next to last anal fin ray; prcf in posterior half of peduncle, tri-pronged, medial prong extending over lower procurrent rays, and lateral prongs extending lateral to lower procurrent rays.

Color. Specimens preserved for long time faded to light brown. Body uniformly black or dark brown, except for triangular area on epiphyseal branch. Pectorals, pelvic, first and second dorsal, anal and caudal fins pigmented also black or dark brown. Internal part of mouth and gill arches black, including skin on toothed area of premaxilla and dentary, over basihyal and basibranchials, roof, floor and lateral wall of mouth, internal part of opercle, membrane between dentaries and premaxillae, and gill arches; gill filaments pale.

Distribution. In the southern portion of western Pacific, from Chatham Islands to west of New Zealand; from 173° W to 167° E, 39° to 48° S ( Fig. 18 A ).

Bathymetric distribution. Meso- to bathypelagic, from 893 to 1223 m (mean 1027 m).

Etymology. The species is named after the North American ichthyologist John Paxton, which now lives in Australia, in recognition of his contributions to the knowledge of the deep-sea ichthyofauna, and all the support given to the development of this work.

Figures

FIGURE 16. Schematic drawing of dentition pattern in the species of Pseudoscopelus: (A) P. altipinnis, ZMUC P. 6546, 111.8 mm; (B) P.paxtoni, NMNZ P. 38679, 234.2 mm, paratype; (C) P. scutatus, ISH 647a-1966, 83.4 mm, paratype; (D) P. odontoglossum, SIO 61-48, 70.2 mm, holotype. Premaxilla (above) and dentary (below); bones with complete dentition are represented on top, and bones with only the sites for teeth attachment on bottom; circes are proportional to diameter of tooth-base; scale bar equals 10.0 mm; C stands for canine and F, for fang.

FIGURE 17. Schematic drawing of the photophore pattern in lateral and ventral views of (A) Pseudoscopelus altipinnis, YPM 2798, 185.8 mm, holotype; (B) P. paxtoni, MNMZ P. 37858, 200.4 mm, paratype. Dashed lines indicate level of anus.

FIGURE 18. Maps of distribution of (A) Pseudoscopelus altipinnis (triangle) and P.paxtoni (star); (B) P. scutatus (star) and P. bothrorrhinos (diamond). Each symbol may represent more than one locality; solid symbols represent type localities.

FIGURE 19. Pseudoscopelus paxtoni: (A) NMNZ P. 28657, 205.1 mm, holotype; (B) MNMZ P. 37858, 200.4 mm, paratype.