Pseudoscopelus odontoglossum, 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 : 61-63

Pseudoscopelus odontoglossum , new species

Figures 16 D , 23 B , 24 C , 26 A , 28 M; Table 10.

Holotype. SIO 61-48 , 70.2 mm, Pacific Plate, 10°24’ S, 161°01’ W, 2700 m, 29–V–1967, R / V Argo .

Paratypes. Five specimens. Pacific, Pacific Plate : FMNH 88163 , 1 , 31.4 mm, 21°23’ N, 158°18’ W, 15– VI –1973, R. E. Young col.; LACM 44397-1 , 1 , 35.4 mm, 21°20’ N, 158°10’ W, 0–325 m, 3–VII–1978 , R / V Kana Keoki ; SIO 70-311 , 1 , 48.7 mm, 26°33’ N, 139°10’ E, 0–2500 m, 1–IX–1970 , R / V Melville ; SIO 71- 290 , 1 , 44.2 mm, 24°18’ S, 154°37’ W, 0–1000 m, 11– III –1971, R / V Thomas Washington ; USNM 391142 (former SIO 68-486 ), 1, 43.3 mm, 27°32’ N, 177°46’ W, 21–IX–1968 , R / V Alexander Agassiz .

Non-type specimen. One specimen. Pacific, Pacific Plate: SIO 70-311 , 1 (cs), 48.7 mm, 26°33’ N, 139°10’ E, 0–2500 m, 1–IX–1970, R / V Melville .

Diagnosis. A species of the Pseudoscopelus astronesthidens species group, which can be distinguished within the group by a unique characteristic: teeth on basihyal and second basibranchial in three rows, 28–40 (vs. teeth on basihyal and second basibranchial in two rows, basihyal teeth 15–25). It can be further distinguished from P. australis by the presence of rakers on first ceratobranchial (vs. rakers absent), palatine teeth in two rows, total teeth 16–26 (vs. palatine teeth in single row, 10–16), and ppf present (vs. ppf absent), and prcf U -shaped (vs. prcf three pronged).

Description. Medium-sized species of Pseudoscopelus , largest specimen examined 70.2 mm SL. Morphometric data summarized in Table 10. General body shape as described for genus with diagnostic characteristics of species and species group.

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

Lateral line complete; lateral-line pores 78 (1), 79 (2*). Pores in temporal canal 2 (3*); supratemporal canal 3 (3*); otic canal 2 (3*); supraorbital canal 6 (3*); supranasal pore 3 (2*), 4 (1); epiphyseal branch 3 (3*); infraorbital canal 12 (3*); preopercular canal 5 (3*); mandibular canal 6 (3*); fifth pore of mandibular canal 2 (3*).

Dentition. Enlarged teeth on premaxilla, dentary and palatine. Premaxilla and dentary illustrated in Figure 16 D . 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 two to four, irregular, longitudinal rows; teeth needle-like, slightly curved, 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 or slightly curved, needle-like, increasing in size from lateral to mesial. Palatine teeth 16 (1), 24 (1*), 26 (1); anteriorly in two rows, teeth straight, needlelike, type 4; posteriorly in single row, teeth three to four, caniniform, type 1, similar to teeth on premaxillary caudal process; palatine teeth.

Teeth on infrapharyngobranchials and fifth ceratobranchial, conical, curved. Teeth on basihyal and second basibranchial 28 (1), 31 (1), 40 (1), type 4, needle-like, in three rows. Teeth absent on other basibranchials. Gill rakers on first epibranchial 1 (3); first ceratobranchial 5 (1), 8 (1), 16 (1); first hypobranchial 7 (1), 8 (2). Gill rakers absent on other elements.

Luminescent organs. Luminescent organs present as discrete photophores on head and body ( Fig. 26 A ). Photophores on head: dnf, inof 1–2, lpf, opf, and pof absent; mxf in single row, parallel to maxilla, from level of mid-eye to posterior third of maxilla, not connected posteriorly with apf; apf in angle between preopercle and maxilla; vnf in small group of few photophores; ppf in 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 to mandibular canal, from halfway between fourth and fifth pores, to halfway between fifth and sixth pores.

Photophores on body: lvf, rtf, scf, spf, svf and trf absent; pf in single row extending to half pectoral fin, on ventral ray; paf continuous with pf, at pectoral-fin axil; vf in single row, to half halfway of pelvic fin, on mesial ray; 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 half of pelvic fin to close to anus; saf in single row, not connected anteriorly at anterior angle, connected posteriorly; prcf in posterior half of peduncle, Y -shaped, prongs extending lateral to lower procurrent rays.

Color. All known specimens faded to light brown. Body uniformly brown, except for triangular area on epiphyseal branch. Pectoral, pelvic, anal, first and second dorsal fins pigmented in their bases; caudal fin brown. Internal part of mouth and gill arches brown, 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.

Identification of juveniles. The smallest specimen recognized has 35.4 mm (LACM 44397-1); the identification was based on the presence of three rows of teeth on second basibranchial, palatine teeth in two rows, teeth present on first ceratobranchial, and dnf present.

Distribution. Pacific Plate; from 154° W to 139° E, 28° N to 24° S ( Fig. 23 B ).

Bathymetric distribution. Meso- to bathypelagic; from 325 to 2700 m (mean 1631 m).

Etymology. From the Greek odont-, meaning tooth, and glosso, means tongue; in reference to the presence of well developed teeth on the bones of the tongue, basihyal and first ceratobranchial.

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 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 26. Schematic drawing of the photophore pattern in lateral and ventral views of (A) Pseudoscopelus odontoglossum, SIO 61-48, mm, holotype. (B) P. lavenbergi, CAS 61407, 63.0 mm, paratype. Dashed lines indicate level of anus.