Ophichthus semilunatus

description

Description. Counts and measurements (in mm) of the holotype: predorsal vertebrae 29; preanal vertebrae 64; total vertebrae 176; preanal lateral-line pores 65. Total length 500; head length 46.8; preanal length 212.0; tail length 287.5; predorsal length 103.5; body depth at gill opening 16.4; body depth at mid-anus 13.0; body width at gill opening 13.3; body width at mid-anus 13.5; snout length 8.9; eye diameter 8.3; upper-jaw length 19.7; gill opening length 4.3; interorbital width 6.1; isthmus width 10.0; pectoral-fin length 14.4; pectoral-fin base 4.5. Body long, subcylindrical, its depth at gill openings 30.5 in TL; tail slightly compressed posteriorly, its depth reduced gradually, its tip elongate (Fig. 3). Head relatively large, branchial basket moderately expanded; head 10.4 in TL; head and trunk 2.4 in TL; snout short, not acute, its length almost equal to eye diameter; no ventral groove on snout; lower jaw included in upper jaw, its tip slightly beyond anterior base of anterior-nostril tube; mouth large, rictus well behind a vertical from posterior margin of eye, with a short, additional fold below rictus; eye large, 2.4 in upper jaw and 5.6 in head; anterior nostril tubul

Two new species of the genus Ophichthus from the western central Pacific Ocean with a redescription of Ophichthus megalops Asano, 1987 (Anguilliformes Ophichthidae)

diagnosis

Diagnosis. A species of Ophichthus with a dark-tipped anal fin, and the following combination of characters: head 9.4 % TL; tail 57.5 % TL; snout not acute, 19.0 % HL; eye large, 93.3 % of snout length and 17.7 % HL; dorsalfin origin well behind pectoral-fin tip by about three pectoral-fin lengths; teeth on maxilla triserial; anterior margin of anus with a half-moon shaped dark marking; SO 1 + 3; POM 6 or 7 + 2; predorsal vertebrae 29, preanal vertebrae 64, and total vertebrae 176.

Two new species of the genus Ophichthus from the western central Pacific Ocean with a redescription of Ophichthus megalops Asano, 1987 (Anguilliformes Ophichthidae)

discussion

Remarks. The new species has the characteristic coloration of a black tip on the anal fin. The character is shared only in seven known congeners. Table 1 shows the selected characters separating the black anal-fin tip species of Ophichthus. The shape of the snout is similar to O. kunaloa McCosker, 1979 and O. tomioi McCosker, 2010 but is easily discerned from the species by the position of dorsal-fin origin (well behind pectoral-fin tip in O. semilunatus sp. nov. vs. not behind in O. kunaloa and O. tomioi). The position of the dorsal-fin origin of the new species is characteristic, having more predorsal vertebrae than other black anal-fin species except O. megalops and O. mystacinus (29 in O. semilunatus sp. nov. vs. 15 – 27 in O. aniptocheilos McCosker, 2010, O. brachynotopterus Karrer, 1982, O. exourus McCosker, 1999, O. kunaloa, and O. tomioi) (Table 2), from O. mystacinus, having a shorter snout (19.0 % HL vs. 22.7 – 28.0 %), larger eyes (17.7 % HL vs. 11.0 – 14.1 %), one + three supraorbital pores (vs. one + four), and a shorter pectoral-fin (30.8 % HL vs. 39.2 – 45.8 %) (McCosker 1999; 2010; Tashiro et al. 2017). The new species closely resembles O. megalops in the position o

Two new species of the genus Ophichthus from the western central Pacific Ocean with a redescription of Ophichthus megalops Asano, 1987 (Anguilliformes Ophichthidae)

distribution

Distribution. Known only from the holotype collected from the northwestern Pacific Ocean, off northeastern Taiwan. Collecting depth unknown but estimated from deepwater.

Two new species of the genus Ophichthus from the western central Pacific Ocean with a redescription of Ophichthus megalops Asano, 1987 (Anguilliformes Ophichthidae)