Pseudoscopelus

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 : 11-13

Key to the species of Pseudoscopelus

(Valid for specimens larger than 45 mm SL)

1 Photophores as discrete organs completely absent, or vestigial; supranasal pores four ...... 2 ( P. aphos species group)

- Photophores present as discrete circular organs on body, fins and head; supranasal pores one to three ...................... 3

2 Vestigial white lines present in place of if, prvf, ptvf, pf, paf, saf, and vf ............ P. parini ( western Pacific to Hawaii)

- Photophores completely absent .............................................................. P. aphos (western North and Central Atlantic)

3 Tip of snout concave; bony plate-like structure on base of first dorsal-fin spines present; mxf, trf, ppf, pf, paf, vf, vaf absent, svf present, prvf and ptvf fused, with single row of photophores, amf restricted to space between third and fourth pores of the mandibular canal; supranasal pore of supraorbital canal 3 ............... 4 ( P. scutatus species group)

- Tip of snout convex; bony plate-like structure on base of first dorsal-fin spines absent; mxf and trf present or not, ppf, pf, paf, vf, vaf present, svf absent, prvf and ptvf separated, amf extending posteriorly to the gap between pores four and five of mandibular canal; supranasal pore of supraorbital canal 1–2.................................................................... 5

4 lpf present ............................................................................................... P. bothrorrhinos (western Pacific and Indian)

- lpf absent ....................................................................................................... P. scutatus (Atlantic, Pacific and Indian)

5 Teeth on basihyal present; teeth on second basibranchial elongated, canine, type 4; palatine teeth type 4; mxf interrupted short, not connected to apf ........................................................................ 6 ( P. astronesthidens species group)

- Teeth on basihyal absent; teeth on second basibranchial small, conical, type 1; palatine teeth type 1; mxf absent or if present connected posteriorly to apf ............................................................................................................................ 8

6 Gill rakers on first ceratobranchial usually absent, or a small tooth present; palatine teeth in a single row, 10–16; ppf absent; prcf oval with three small prongs ................. P. australis (southern hemisphere: Atlantic, Indian and Pacific)

- Teeth on first ceratobranchial present, 2–16; palatine teeth in two rows, 15–38; ppf present; prcf two U -shaped ..... 7

7 Teeth on basihyal and second basibranchial in two rows, basihyal teeth 10–16; teeth on second ceratobranchial present .............................................................................................................. P. astronesthidens (western North Atlantic)

- Teeth on basihyal and second basibranchial in three rows, basihyal teeth 20–26; teeth on second ceratobranchial absent .............................................................. P. odontoglossum , new species (western North and middle of Pacific)

8 trf in a broad band of three to six rows, total photophores more than 20; prvf short, not reaching anterior tip of pelvic griddle; ptvf short, anteriorly not reaching anus, and extending only halfway to pelvic-fin origin; mxf absent ............ ......................................................................................................................................... P. lavenbergi (eastern Pacific)

- trf in a single row, total photophores less than15; prvf elongated, reaching anterior tip of pelvic girdle; ptvf elongate, anteriorly extending next to anus, and to very close to pelvic-fin origin; mxf present ............................................... 9

9 trf in single, straight row of widely spaced photophores, not forming a medial cluster; mxf in single irregular row, photophores widely spaced; apf present; supraorbital pores 6 .................................... 10 ( P. altipinnis species group)

- trf in single row of closely spaced photophores, with a circular cluster in midline; mxf in single straight row, with spaced photophores; apf absent; supraorbital pores 5...................................................... 11 ( P. scriptus species group)

10 Premaxillary and dentary teeth moderately developed, but not long enough to reach other side of mouth; only last tooth of lateral series of premaxilla type 1; ppf present or absent .............. P. altipinnis (Atlantic, Indian and Pacific)

- Premaxillary and dentary teeth very enlarged, reaching other side of mouth; last four to six teeth of external series of premaxilla type 1; ppf absent ......................................................................................................................................... ............................................ P. paxtoni , new species ( western South Pacific , from New Zealand to eastern Australia)

11 Total vertebrae 31, precaudal 14 .................................................. P. cephalus (western Central Pacific, off Indonesia)

- Total vertebrae 35–36, precaudal 18–19 .................................................................................................................... 12

12 Premaxillary mesial series of teeth in a single row; teeth 3–4; premaxillary width 10–14% in premaxillary length, lvf present ........................................................................................................................................................................ 13

- Premaxillary mesial series of teeth in three to four rows; teeth 9–13; premaxillary width 10–17 % in premaxillary length, lvf absent ....................................................................................................................................................... 14

13 Hooked teeth on lateral series of dentary and premaxilla present, teeth visible from dorsal and ventral views, spf present ....................................................................................................... P. obtusifrons (Atlantic, Indian, and Pacific)

- Hooked teeth on lateral series of dentary and premaxilla absent, teeth not visible from dorsal and ventral views; spf absent .................................................................................. P. pierbartus (North Atlantic and western South Atlantic)

14 Teeth abruptly increasing in size from lateral to medial, those in internalmost row of mesial series of premaxilla and dentary at least twice as long as the remaining teeth; premaxilla width 10–14% in premaxillary length...................... ................................................................ P. cordilluminatus , new species (Indian, eastern South and Central Atlantic)

- Teeth gradually increasing in size from lateral to medial, those in internalmost row of mesial series of premaxilla and dentary slightly longer than remaining teeth; premaxilla width 15–17 % in premaxillary length ........................... 15

15 saf not extending anteriorly to level of anus; internal part of mouth mostly clear, except for a few dusky areas ......... ............................................................................................................. P. scriptus (western North and Central Atlantic)

- saf extending anteriorly beyond the level of anus; mouth cavity entirely dark, including gill arches .......................... ...................................................................................................................... P. sagamianus ( eastern Pacific to Hawaii)