Bathyuroconger dolichosomus, Smith & Ho & Tashiro, 2018

Smith, David G., Ho, Hsuan-Ching & Tashiro, Fumihito, 2018, Eels of the genus Bathyuroconger in the northwestern Pacific, with descriptions of four new species (Anguilliformes: Congridae), Zootaxa 4454 (1), pp. 147-167 : 156-157

Bathyuroconger dolichosomus sp. nov.

English name: Long-body large-toothed conger

Figs. 5D , 6 ; Tables 1, 2

Holotype. ASIZP 65175 , 350 + mm, off Daxi fishing port, Yilan, NE Taiwan, northwestern Pacific Ocean, 24 Apr. 2005, coll. H.- C. Ho

Diagnosis. A species of Bathyuroconger with a moderately small gill opening, its diameter 8.8% of head length, close to but not against pectoral-fin base; head length 3.2 times in trunk length, 23.9 % PAL; predorsal length 28.9 % PAL, trunk length 76.1 % PAL. Preanal lateral-line pores 61. Preanal vertebrae 63; precaudal vertebrae 70. Body lightly brownish dorsally and pale ventrally.

Description. Measurements in % PAL:PDL 28.9, HL 23.9, TR 76.1, DA 9.6. In % HL: S 26.4, E 11,4, IOW 26.9, UJ 37.4, GO 8.8, IB 26.9, PL 29.9. Pores: PALL 61, PDLL 10, PPLL 6, SO 3, IO 5, POM 10, ST 1. Vertebrae: PDV 12, PAV 63, PCV 70.

Body slender, cylindrical anteriorly, gradually tapering and compressed posteriorly; trunk very long, 3.2 times head length. Tail broken and regenerated. Dorsal fin begins above posterior half of pectoral fin. Head moderately large, rounded, slightly deeper than body, upper jaw protrudes slightly but distinctly beyond lower jaw. Snout short and blunt, rounded in dorsal view, 2.3 times eye diameter. Eye moderately large, over posterior third of upper jaw, its posterior margin at level of rictus; interorbital space relatively broad, its width greater than eye diameter. Anterior nostril tube-like, at front of snout; posterior nostril in front of mid-eye, a simple pore. Gill opening small, located anterior to pectoral fin, its upper end at level of lower pectoral-fin base, distance from gill opening to fin base less than diameter of gill opening.

Head pores moderately enlarged, not elongate and slit-like. Supraorbital pores 3; first pore at tip of snout on edge of upper lip, opening downward; second pore above first and anterior to base of anterior nostril; third pore larger, directly above anterior nostril; no pores on interorbital space. Infraorbital pores 5; first pore immediately behind anterior nostril; second between anterior and posterior nostrils; third below or slightly before anterior margin of eye; fourth below and slightly behind mid-eye; fifth behind rictus. Preoperculomandibular pores 10; 7 on mandibular section and 3 on preopercular, the last one at about level of first lateral-line pore. A single supratemporal pore with tube-like rim, anterior to level of first lateral-line pore. Lateral line complete, lateral-line pores large; predorsal 9, prepectoral 6, preanal 61.

Vertebrae: predorsal 12; preanal 63; precaudal 70; total unknown.

Teeth large and pointed, generally smaller than those of B. vicinus . Intermaxillary teeth in two transverse rows, 4 in anterior row and 6 in posterior, exposed when mouth closed. Vomer with 2 median teeth, the anterior one much larger, and 4 small teeth behind. Maxilla with 3 irregular rows of teeth on anterior portion, becoming 2 rows posteriorly, those on the outermost row larger and scattered in arrangement. Dentary with 4 irregular rows of enlarged teeth on anterior portion, those on outer 2 rows fang-like and exposed when mouth fully closed, gradually narrowing to 2 rows posteriorly, those on outermost row larger.

Coloration. Fresh color unknown. In preservative, dorsal half of head and anterior two-thirds and posterior one-third of body brown, becoming paler on ventral surface; ventral half of anterior two-thirds of body covered by scattered pigmentation; no clear boundary between the pigmented and unpigmented areas. Pectoral fin transparent. Dorsal fin white anteriorly, gradually becoming pale at base with a broad black margin posteriorly. Anal fin abnormal, covered by skin similar to body color. Oral cavity and tongue grayish; gill chamber grayish, gill cover region grayish from outside view. Peritoneum blackish; gut and stomach black.

Distribution. Known only from the holotype collected from northeastern Taiwan.

Etymology. Named from Greek dolichos long + soma body, referring to the diagnostic characteristic of its long body. Treated as an adjective.

Remarks. Bathyuroconger dolichosomus sp. nov. is distinguished from all the other species by its long trunk, more than 3 times the head length, and the correspondingly high number of preanal vertebrae (63 vs 43‒55) and precaudal vertebrae (70 vs 52‒63). The holotype and only known specimen is missing a substantial part of its tail, so the total length and the total number of vertebrae are unknown. The characters listed above, however, are sufficient to distinguish it from all other known species.

Figures

FIGURE 5. Lateral view of head of four Bathyuroconger species. A. B. albuS sp. nov., USNM 400322, paratype, 493+ mm TL. B. B. vicinuS, USNM 405028, 522+ mm TL. C. B. cf. vicinuS, USNM 135270, 445 mm TL. D. B. dolichoSomuS sp. nov., holotype, ASIZP 65175, 350+ mm TL.

FIGURE 6. Bathyuroconger dolichoSomuS sp. nov., holotype, ASIZP 65175, 350+ mm TL.