Pseudoscopelus cordilluminatus, 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 : 34-36

Pseudoscopelus cordilluminatus , new species

Figures 5 D , 7 A , 13 B , 14 A–B , 28 F; Table 5.

Pseudoscopelus scriptus (non Lütken) Prokofiev and Kukuev 2005 [in part, list of material, specimens from Gulf of Guinea]; 2006a [in part, specimens from Gulf of Guinea, figures 2 B, D, G], 2006c [species key], 2008 [in part, specimens from Gulf of Guinea, figures 157, 159, 162].

Holotype. MCZ 161017 , 77.0 mm, Eastern Atlantic , Guinean, 0º00’, 19º45’ W, 0–1164 m, 20–IV–1965, R / V Trident.

Paratypes. Three specimens. Atlantic, Guinean Province : CAS 223102, 1 , 88.7 mm, 8°35’ S, 12°51’ E, 548– 526 m, 11–IV–2005, R / V Dr. Fridtjof Nansen. Indian : BMNH 2003.4.23.51, 1, 87.3 mm, 10º16’ N, 57º56’ E, 14– III –1964, R. R.S. Discovery. Pacific, West Pacific : SIO 77-171, 1 , 97.3 mm, 4°40.2’ S, 125°32.8’ E, 0–1500 m, 26– VIII –1976, R / V Thomas Washington .

Non-type (juvenile, tentative identification). One specimen. Indian: USNM 200533 , 1 , 24.4 mm, 4º01’ S, 65º00’ E, 615 m, 30–V–1964, R / V Anton Bruun .

Diagnosis. A species of the Pseudoscopelus scriptus species group, which can be distinguished within the group by the unique dentition pattern of the premaxilla: mesial series in rows of two to three teeth, with first and second teeth much smaller than innermost tooth (vs. single row in P. pierbartus and P. obtusifrons ; and teeth gradually increasing in size in P. cephalus , P. sagamianus , and P. scriptus ). It can be further distinguished from P. scriptus by saf extending anteriorly beyond and around anus (vs. saf not extending anteriorly to anus), from P. cephalus by vertebral count (total vertebrae 35–36, precaudal 18–19 vs. 31, 14 in P. cephalus ), and from P. sagamianus by melanophores inside mouth restricted to tooth insertion region (vs. internal area of mouth and gill arches completely black).

Description. Medium-sized species of Pseudoscopelus , largest specimen examined 97.3 mm SL. Morphometric data summarized in Table 5. General body shape as described for genus with diagnostic characteristics of species and species group.

First dorsal-fin rays vii (2), viii (3*); second dorsal-fin rays ii+20 (4*), ii+21 (1); anal-fin rays ii+20 (2) iii+18 (1), iii+20 (2*); pectoral-fin rays 12 (2*), 13 (3); pelvic-fin rays I+5 (5*); caudal-fin rays i+7+8+i (3), i+8+7+i (2*). Branchiostegal rays 7 (5*). Pre-caudal vertebrae 17 (1*), 18 (2); total vertebrae 36 (3*).

Lateral line complete; lateral-line pores 75 (4*), 76 (1). Pores in temporal canal 2 (5*); supratemporal canal 3 (5*); otic canal 2 (5*); supraorbital canal 6 (5*); supranasal pore 2 (5*); epiphyseal branch 2 (4*), 3 (1); infraorbital canal 11 (5*); preopercular canal 5 (5*); mandibular canal 6 (5*); fifth pore of mandibular canal 2 (4*), 1 (1).

Dentition. Enlarged teeth on premaxilla, dentary and palatine. Premaxilla and dentary illustrated in Figure 5 D . Premaxilla narrow, widest point of premaxillary body 10–14 % in premaxillary length.

Premaxillary teeth on head, neck, body and caudal process. Lateral series in single longitudinal row, along lateral edge of premaxillary head, neck, body and caudal process; teeth conical, slightly curved. Canine and fang on ventral shelf of premaxillary head. Middle and mesial series on ventral shelf of premaxillary body. Middle series in single, longitudinal row, teeth conical, straight. Mesial series in transverse rows, each row with one to three teeth; lateral teeth short, conical, straight; teeth in medial edge of premaxilla elongate, needle-like, straight.

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 in transverse rows of one to four teeth; teeth needle-like, straight, abruptly increasing in size, lateral teeth half length of medial. Palatine teeth 8 (1), 9 (2), 11 (1), 16 (1*); in single, longitudinal row.

Teeth on infrapharyngobranchials and fifth ceratobranchial, conical, curved. Teeth on second basibranchial 5 (1), 6 (1), 7 (1), 9 (1*), 10 (1), conical, in V -shaped or single, irregular row. Teeth absent on basihyal and other basibranchials. Gill rakers on first epibranchial 0 (5*); first ceratobranchial 6 (1), 7 (1), 8 (2*), 9 (1); first hypobranchial 3 (1), 5 (1), 6 (1), 7 (1*), 8 (1). Gill rakers absent on other elements.

Luminescent organs. Luminescent organs present as discrete photophores on head and body ( Fig. 13 B ) Photophores on head: apf, dnf, inof 1–2, lpf, opf, and pof absent; mxf elongated, in single row, parallel to maxilla, from level of posterior margin of eye to angle between preopercle and dentary; vnf often absent, if present in small group just posterior to anteriormost supraorbital pore; ppf as small patch in ventral edge of interopercle; amf in one to three rows, medial to mandibular canal, from first pore to halfway between third and fourth pores; pmf in one to three rows, lateral to mandibular canal, from 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 continuous with vf and trf, extending over base of pelvic rays three to five; if and prvf continuous or separated by distance of less than two photophores wide, in irregular rows of two photophores, from isthmus to anterior edge of pelvic girdle; ptvf in one to three rows, from posterior half of pelvic fin to close to anus; trf laterally in single row, with medial circular group of photophores; saf in two rows, with smaller photophores closely spaced and ventral, and larger photophores widely spaced and dorsal, heart-shaped, extending to level of or anterior to anus, and connected posteriorly; prcf in posterior half of peduncle, oval-shaped, three-pronged, medial prong extending over anteriormost lower procurrent rays.

Color. Most specimens examined faded to light brown or bleached white; single specimen (CAS 223102) with preserved color. Body uniformly black or dark brown, except for triangular area on epiphyseal branch. Pectoral, pelvic, and first dorsal fins slightly pigmented on fin-rays; second dorsal and anal fins with melanophores extending to fin membranes, especially at fin bases; caudal fin uniformly black, except at tip of rays. Internal area of mouth and gill arches pale.

Distribution. In the eastern South and Central Atlantic, from Middle Atlantic to off Angola; from 20º W to 12º W, 0º to 9º S. From the Indian Ocean to western Pacific from off Oman to Indonesia; from 57º E to 125º E, 10º N to 5º S ( Fig. 7 A ).

Bathymetric distribution. Meso- to bathypelagic, from 537 to 1164 m (mean 954 m).

Identification of juveniles. A small specimen of 24.4 mm (USNM 200533) was tentatively identified based on the shape of saf, anteriorly passing level of anus and connected posteriorly.

Etymology. From the Latin cordis, means heart, and luminosus, full of light, in a reference to the heartshaped saf.

Figures

FIGURE 5. Schematic drawing of dentition pattern in the species of Pseudoscopelus: (A) P. scriptus, ZMUC P 65171. 70.0 mm, holotype; (B) P. obtusifrons, LACM 20074, 100.7 mm; (C) P. pierbartus, LACM 56615, 133.4 mm; and (D) P. cordilluminatus, SIO 77-171, 97.3 mm, paratype. 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 7. Maps of distribution of (A) Pseudoscopelus scriptus (diamond), P. sagamianus (star), P. cephalus (asterisk), and P. cordilluminatus (circle); (B) P. obtusifrons (cross), and P. pierbartus (triangle). Each symbol may represent more than one locality; solid symbols represent type localities.

FIGURE 13. Schematic drawing of the photophore pattern in lateral and ventral views of (A) Pseudoscopelus pierbartus, USNM 240687, 87.1 mm; and (B) P. cordilluminatus, BMNH 2003.4.23.51, 87.3 mm, paratype. Dashed lines indicate level of anus.

FIGURE 14. Pseudoscopelus cordilluminatus: (A) MCZ 161017, 77.0 mm, holotype; (B) CAS 223102, 88.7 mm, paratype.