Pseudoscopelus astronesthidens Prokofiev & Kukuev 2006

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 : 55-58

Pseudoscopelus astronesthidens Prokofiev & Kukuev 2006

Figures 23 B , 24 A , 25 A , 28 K; Table 9.

Pseudoscopelus astronesthidens Prokofiev and Kukuev 2006c : S27–S32, figures 2 D, 2 G–J, 3 C, 4, 5 [type locality western North Atlantic, 37°34’ N, 59°56’ W, holotype ZM MGU 16455, 150.0 mm]; Prokofiev and Kukuev 2006d: 71 [second species description]; 2008: 53–62, figures 10, 11, 26, 35–38, 63, 72, 76–78, 82, 85, 102–111 [species account].

Pseudoscopelus vorax Lavenberg 1974: 234–246 , figures 46, 48, 49 [North Atlantic; name not available in accordance to the ICZN 1999].

Pseudoscopelus voratus Lavenberg 1974: 49 [misspelling of P. vorax , name not available in accordance to the ICZN 1999].

Pseudoscopelus altipinnis (non Parr 1933) Prokofiev and Kukuev 2005: 752, figure 2 [questionable].

Diagnosis. A species of the Pseudoscopelus astronesthidens species group, which can be distinguished within the group by a single characteristic: rakers on second ceratobranchial present (vs. rakers on second ceratobranchial absent). It further differs from P. odontoglossum by having teeth on basihyal and second basibranchial in two rows, 19–25; (vs. teeth on basihyal and second basibranchial in three rows, 28–40); and from P. australis by rakers on first ceratobranchial present, 2–9 (vs. usually absent, a single raker rarely present on proximal portion); palatine teeth in two rows, 15–38 (vs. palatine teeth in single row, 10–16); ppf present (vs. ppf absent); prcf two pronged, U -shaped (vs. prcf with three small prongs).

Description. Medium-sized species of Pseudoscopelus , largest specimen examined 143.0 mm SL. Morphometric data summarized in Table 9. General body shape as described for genus with diagnostic characteristics of species and species group.

First dorsal-fin rays vi (1), viii (4), ix (1); second dorsal-fin rays ii+21 (1), ii+22 (3), ii+23 (2); anal-fin rays iii+20 (1), iii+21 (2), iii+23 (1), iv+22 (1), iv+23 (1); pectoral-fin rays 11 (1), 12 (3), 13 (2); pelvic-fin rays I+5 (6); caudal-fin rays i+7+8+i (5), i+8+8+i (6). Branchiostegal rays 7 (6). Pre-caudal vertebrae 17 (2), 18 (6), 19 (1); total vertebrae 36 (2), 37 (7).

Lateral line complete; lateral-line pores 75 (1), 77 (1), 78 (3). Pores in temporal canal 2 (6); supratemporal canal 3 (6); otic canal 2 (6); supraorbital canal 6 (6); supranasal pore 3 (6); epiphyseal branch 1 (1), 3 (4), 4 (1); infraorbital canal 12 (6); preopercular canal 5 (6); mandibular canal 6 (6); fifth pore of mandibular canal 2 (6).

Dentition. Enlarged teeth on premaxilla, dentary and palatine. Teeth arrangement as illustrated for Pseudoscopelus odontoglossum . 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; posterior ten to 12 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 reaching premaxillary neck. Middle series in three, irregular transverse rows; teeth needle-like, straight, gradually increasing in size from lateral to medial. Mesial series in transverse rows, each row with one to four teeth; teeth needle-like, 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 15 (1), 16 (1), 21 (1), 29 (1), 33 (1), 38 (1); anteriorly in two rows, teeth needle-like, type 4; posterior three to four teeth in single row, teeth conical, type 1, similar in shape to teeth on caudal process; palatine teeth.

Teeth on infrapharyngobranchials and fifth ceratobranchial, conical, curved. Teeth on basihyal and second basibranchial 19 (1), 21 (1), 23 (3), 25 (1), type 4, needle-like, in two rows. Teeth absent on other basibranchials. Gill rakers on first epibranchial 0 (6); first ceratobranchial 2 (2), 5 (2), 8 (1), 9 (1); first hypobranchial 5 (2), 6 (2), 10 (1), 12 (1). Gill rakers absent on other elements.

Luminescent organs. Luminescent organs present as discrete photophores on head and body ( Fig. 25 A ). Photophores on head: dnf, inof 1–2, lpf, opf, pof, and absent; mxf short, in single row, parallel to maxilla, from level of mid-eye to posterior third of maxilla, not connected to apf posteriorly; apf in angle between preopercle and maxilla; vnf in small group of few photophores; ppf in ventral edge of interopercle; amf in one to three rows, medial to mandibular canal, from slightly anterior to third pore to fourth pore; pmf in one to three rows, lateral mandibular canal, from halfway between fourth and fifth pores to near sixth pore.

Photophores on body: lvf, rtf, scf, spf, svf and trf absent; pf in single row, in ventral ray along pectoral fin; paf continuous with pf, at pectoral-fin axil; vf in single row, along mesial pelvic-fin ray to first third of pelvic fin; vaf continuous with vf; if short, in two rows, from isthmus to cleithrum; prvf short, in two rows, from cleithrum to anterior part of pelvic bone; ptvf in two rows, from posterior third of pelvic fin to close to anus; saf in single row, not connected anteriorly at anterior angle, neither posteriorly; prcf in posterior half of peduncle, U -shaped, surrounding 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. Pectoral, pelvic, first and second dorsal, and anal fin mostly hyaline, pigmented at their bases; caudal fin dusky. Internal part of mouth pigmented including area of teeth insertion of dentary and premaxilla, roof, lateral sides and floor of mouth, skin over basihyal, basibranchials, and gill arches; gill filaments pale.

Identification of juveniles. The smallest specimen recognized has 31.9 mm (CAS-SU 66492); the identification was based on the presence of teeth on basihyal, second basibranchial, first ceratobranchial and palatine, and the presence of ppf.

Distribution. In the western North Atlantic; from 15° to 65° W, 60° to 30° N ( Fig. 23 B ).

Bathymetric distribution. Meso- to bathypelagic, 154 to 1482 m (mean 858 m).

Figures

FIGURE 23. Map of distribution of (A) Pseudoscopelus aphos (diamond), P. lavenbergi (cross), and P. parini (circle); (B) P. astronesthidens (cross), P. australis (asterisk), and P. odontoglossum (star). Each symbol may represent more than one locality; solid symbols represent type localities.

FIGURE 24. Pseudoscopelus astronesthidens: (A) MCZ 163443, 71.8 mm. Pseudoscopelus australis: (B) NMNZ P. 40787, 197.4 mm. Pseudoscopelus odontoglossum: (C) SIO 61-48, 70.2 mm, holotype

FIGURE 25. Schematic drawing of the photophore pattern in lateral and ventral views of (A) Pseudoscopelus astronesthidens, MCZ 163443, 71.8 mm; (B) P. australis, NMNZ P. 40787, 197.4 mm. Dashed lines indicate level of anus.