Pseudoscopelus pierbartus Sptiz, Quéro & Vayne 2007

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 : 30-34

Pseudoscopelus pierbartus Sptiz, Quéro & Vayne 2007

Figures 5 C , 7 B , 12 A–G , 13 A , 28 E; Table 5.

Pseudoscopelus pierbartus Spitz et al. 2007: 333–339 , figure 2 [type locality western North Atlantic , Golfe de Gascoigne, France, holotype MHNLR 2005171 , 138.0 mm].

Pseudoscopelus scriptus (non Lütken) Prokofiev and Kukuev 2005 [in part, list of material, specimens from western North Atlantic]; 2006a [in part, specimens from western North Atlantic, figures 2 A, C, G], 2006c [species key], 2008 [in part, specimens from western North Atlantic, figures 155, 156, 159, 162].

Diagnosis. A species of the Pseudoscopelus scriptus species group, which can be distinguished within the group by a combination of characteristics: mesial series of premaxillary teeth in a single row, with two to four teeth (vs. medial series in three to four rows, with 20 or more teeth in P. scriptus , P. cephalus , P. sagamianus , and P. cordilluminatus ), dentary teeth in two series, lateral and medial, each with a single row (vs. dentary teeth with two series, lateral in single row and mesial with three or more rows); teeth at the anterior edge of premaxilla recurved, dentary inserted on the ventral edge of the bone and pointing mesially or caudally (vs. teeth of lateral series extremely curved with anterior teeth inserted in the lateral edge of bone, turned outwards).

Description. Middle-sized species, the largest specimen examined 179.8 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 (3), viii (3), ix (1); second dorsal-fin rays ii+18 (1), ii+19 (2), ii+20 (2), ii+21 (1), ii+22 (1); anal-fin rays ii+19 (2), iii+17 (1), iii+18 (2), iii+19 (3), iii+20 (1); pectoral-fin rays 13 (6), 14 (2); pelvic-fin rays I+5 (7); caudal-fin rays i+7+8+i (7). Branchiostegal rays 7 (7). Pre-caudal vertebrae 16 (1), 17 (1), 18 (5), 19 (1); total vertebrae 35 (2), 36 (8).

Lateral line complete; lateral-line pores 72 (2), 74 (3), 76 (1), 77 (1). Pores in temporal canal 2 (7); supratemporal canal 3 (7); otic canal 2 (7); supraorbital canal 5 (7); supranasal pore 1 (1), 2 (6); epiphyseal branch 2 (5), 3 (2); infraorbital canal 11 (6), 13 (1); preopercular canal 5 (7); mandibular canal 6 (7); fifth pore of mandibular canal (2).

Dentition. Enlarged teeth on premaxilla, dentary and palatine. Premaxilla and dentary illustrated in Figure 5 C . Premaxilla narrow, widest point of premaxillary body 10–13% 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, strongly curved, but not hooklike as in Pseudoscopelus obtusifrons . 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 single, longitudinal row; teeth conical, slightly curved.

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, curved. Mesial series in single, longitudinal row, teeth conical, curved. Palatine teeth 7 (3), 8 (1), 9 (2), 10 (1); in single, longitudinal row.

Teeth on infrapharyngobranchials and fifth ceratobranchial, conical, curved. Teeth on second basibranchial 8 (1), 9 (1), 10 (1), 12 (1), 13 (1), 14 (1), conical, in V -shaped or two rows. Teeth absent on basihyal and other basibranchials. Gill rakers on first epibranchial 0 (6); first ceratobranchial 8 (1), 9 (1), 11 (2), 12 (1), 15 (1); first hypobranchial 2 (1), 6 (2), 11 (1), 12 (1), 13 (1). Gill rakers absent on other elements.

Luminescent organs. Luminescent organs present as discrete photophores on head and body ( Fig. 13 A ). 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 in triangular patch, or straight line of few photophores; ppf in small patch on ventral edge of interopercle; amf in one to two rows, medial mandibular canal, from second pore to fourth pore; pmf in one to two rows, lateral to mandibular canal, from halfway between fourth and fifth pores to halfway between fifth and sixth pores.

Photophores on body: rtf, scf, and svf absent; spf in single row, with four to five photophores; 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; lvf at base of first pectoral fin; vaf continuous with vf and trf, extending over base of pelvic rays three to five; if and prvf continuous, in irregular two rows, from isthmus to anterior edge of pelvic girdle; ptvf in two rows, from posterior half of pelvic fin to close to anus; trf 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 slightly anterior anus, not connected posteriorly; prcf in posterior half of peduncle, oval-shaped, three-pronged, extending over anteriormost lower procurrent rays.

Color. Most specimens examined faded to clear brown. Recently collected specimens uniformly black or dark brown, except for triangular area on epiphyseal branch. Pectoral and pelvic fins mostly hyaline, with few melanophores on rays; anal, first and second dorsal fins with melanophores uniformly distributed over rays, more concentrated on fin base; and caudal fin entirely black. Internal area of mouth and gill arches pale.

Distribution. In the North Atlantic, from off the United States to France, and in the western South Atlantic, from Brazil; from 48º N to 20º S, 67º W to 4º W ( Fig. 7 B ).

Bathymetric distribution. Meso- to bathypelagic, from 829 to 1770 m (mean 1069 m); juveniles are known from 50 to 1025 m.

Remarks. Pseudoscopelus pierbartus was not listed in Lavenberg (1974). Prokofiev and Kukuev (2006 a, 2006c, 2008) incorrectly identified it as P. scriptus . Prokofiev and Kukuev (2008) proposed that P. pierbartus was possibly a synonym of P. sagamianus , and considered its status as species inquirenda and nomen dubium. Spitz et al. (2007) diagnosed it based on the shape of prcf, formed by three double lines forming an arrow pointing forward, length of pectoral fin, extending to sixth ray of second dorsal fin, and teeth curved at anterior end of premaxilla. None of these characteristics, however, is useful to diagnose the species. The prcf in all species of the Pseudoscopelus scriptus species group is three pronged posteriorly with lateral prongs small, varying to slightly oval. Other species of Pseudoscopelus also have the three pronged pattern prcf: P. altipinnis , P. paxtoni , P. scutatus , P. australis and P. lavenbergi ( Figs. 17 , 21 , 25 , 26 ). The prcf is also extremely variable in P. pierbartus from small prongs to almost oval ( Figs. 12 D–G ). Within the group, other species also have elongated pectoral fin: P. scriptus , P. sagamianus and P. cordilluminatus . Finally, the anterior teeth of premaxilla curved should not be confused with the hook-like teeth of P. obtusifrons .

Pseudoscopelus pierbartus is a very similar species to P. scriptus and can only be separated by having fewer teeth in the middle series of premaxillary teeth, organized in a single row. It can be tentatively separated from P. scriptus by the shape of saf, which extends anteriorly to the level of anus – but this characteristic varies in some specimens. This last characteristic can be used to tentatively identify the juveniles with less than 44.5 mm, before dentition is completely formed.

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 12. Pseudoscopelus pierbartus: (A) USNM 240687, 87.1 mm; (B) ZMUB 16378, 1, 179.8 mm; (C) MCZ 164762, 94.1 mm, paratype in lateral view of head. Peduncle of P. pierbartus in ventral view with variation of shape of prcf: (D) USNM 240687; (E) LACM 56619-1; (F) MNRJ 26699; (G) ZMUC 16378.

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 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 21. Schematic drawing of the photophore pattern in lateral and ventral vies of (A) Pseudoscopelus scutatus, ISH 567b-c/1966, 80.4 mm, paratype; (B) P. bothrorrhinos, SIO 07-6, 39.6 mm, paratype.

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.

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.