Bathycongrus melanostomus Huang & Ho & Chen & Chan 2022, sp. nov.
Creators: name: Huang, Jian-Fu
name: Ho, Hsuan-Ching
name: Chen, Hong-Ming
name: Chan, Tin-Yam
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Anguilliformes
Congridae
Bathycongrus
Bathycongrus melanostomus

description: Bathycongrus melanostomus sp. nov.
English name: Black mouth conger
Figs. 1A–D, 2A–C, 3, 4; Table. 1
Holotype. TOU-AE 7271 (439 mm TL), ca. 23°29'N, 121°30'E, off Shihtiping, Hualien, eastern Taiwan, hook and line, ca. 300 m, 23 Jan. 2015, coll. J.-S. Chiu.
Paratypes. TOU-AE 7272 (371 mm TL), ca. 23°45'N, 121°34'E, off Shuilien, Hualien, eastern Taiwan, hook and line, ca. 300 m, 27 Jan. 2015, coll. J.-S. Chiu. NMMB-P36072 (formerly TOU-AE 5560) (420 mm TL), ca. 23°18'N, 121°26'E, off Changbin, Taitung, eastern Taiwan, hook and line, ca. 300 m, 13 Jun. 2010, coll. J.-S. Chiu.
Diagnosis. A moderately elongate species of Bathycongrus with uniformly small teeth on vomer forming an oval patch; a strongly reduced caudal fin; abdomen, mouth cavity and gill chamber blackish. It can be further distinguished from the congeners by dorsal and anal fins grayish with black margins; a short, broad and blunt snout, intermaxillary teeth barely exposed when mouth closed; pre-anal vertebrae 31, precaudal vertebrae 41; total vertebrae 133–135; and pre-anal lateral-line pores 31.
Description. The following values are given for the holotype, followed by the range of the two paratypes in parentheses.
Body rather stout, robust, rounded in cross section anteriorly, becoming more compressed behind anus and posterior portion; head moderately slender, head depth and width slightly smaller than those of trunk; trunk moderately long, its length 1.5 (1.6–1.7) times of head length; tip of tail rounded, not filiform; anus situated at near anterior two fifths of total length (when tail complete), pre-anal length 36.4 in TL; tail relatively short, tail length 63.6 in TL.
Dorsal-fin origin behind tip of pectoral fin, continuous around tip of tail with caudal and anal fins. Anal fin begans immediately behind anus. Pectoral fin well developed, pointed distally with a narrow base. Caudal-fin rays strongly reduced, with membranes forming a small flap. Gill opening large, similar to eye diameter or slightly smaller in length, its upper end nearly opposite to middle of pectoral-fin base. Interbranchial width much broad, more than twice of width of gill opening (Fig. 1).
Head relatively large and robust, its length 14.6% (13.5–14.6%) TL, deepest at about occiput, slightly tapering anteriorly to this point; dorsal profile nearly flat from occiput to internasal space; snout short and rounded, its length 1.7 (1.6–1.7) times eye diameter, slightly projecting beyond lower jaw; lower jaw longer than snout; fleshy part of snout without median keel on underside, projecting anteriorly beyond anterior end of intermaxillary tooth patch; rictus below middle of eye.
Anterior nostril tubular, near tip of snout, directed ventrolaterally. Posterior nostril elliptical, with clear rim, in front of eye above mid-eye level. Upper lip with flange strongly reduced, lower lip with a well-developed downturned flange. Tongue free, long, and broad.
Lateral line complete, first pore on each side slightly enlarged, the canal extended to caudal-fin base; 13 pores before dorsal-fin origin, 5 pores before pectoral-fin base, 31 pores before anal-fin origin; total pores 109 (108–109), last one running to about 1 head length before rear tip.
Head pores various in size (Fig. 3). Supraorbital canal with 3 pores, the first (ethmoidal pore) on ventral side of snout tip, just ahead of lip; the second enlarged and immediately in front of anterior nostril; the third greatly enlarged and immediately above anterior nostril. Infraorbital canal with 5 pores, first pore at dorsal-posterior corner of anterior nostril; the second and third enlarged, between anterior and posterior nostrils, both shaded by upper flange; the fourth small, below anterior margin of eye; the fifth small, behind rictus. No pore on frontal region and behind eye. Preoperculomandibular canal with 9 pores, 5 before and 4 behind rictus, second and posteriormost 2 pores (preopercular) enlarged. Supratemporal with a single, small medial pore.
Teeth (Fig. 4) uniformly small in size, conical to blunt. Intermaxillary in about 5 transverse rows, not well separated from maxillary and vomerine teeth, barely excluded from closed mouth. Maxillary and mandibular teeth in bands, wider anteriorly, roughly in 4 or 5 rows in anterior three-fourths, followed by a narrower, curved band of 2 or 3 rows of smaller teeth; outermost teeth slightly smaller than those of inner rows. Vomerine teeth blunt, shorter than those of intermaxillary, forming an oval patch, patch with length longer than width, reaches to level of posterior nostril, in about 8 rows middly.
Coloration. When fresh (Figs. 1A–B, 2A–B), body uniformly dark grey to brown; vertical fins black with gray bases. Dark papillae outlining supratemporal canal and along dorsal surface; an indistinct patch of pigments on opercle in front of pectoral-fin base. Pectoral fin yellowish with black margin. Lateral-line pores white. Anterior portions of snout, lips and chins whitish. Mouth cavity, gill chamber black. When preserved (Figs. 1C, 2C), body uniformly dark brown. Anterior portions of snout, lips and chins whitish. Mouth cavity, gill chamber, peritoneum, stomach, and intestine black. Pectoral fin brown with black margin. Lateral-line pores white.
Measurement for holotype (in mm): total length 439.0; head length 64.0; predorsal length 89.0; preanal length 160.0; trunk length 96.0; tail length 279.0; depth at gill opening 34.9; width at gill opening 22.4; depth at mid-anus 34.3; eye diameter 8.6; interorbital width 15.6; snout length 14.5; interbranchial width 17.2; pectoral-fin length 22.3; gill-opening length 9.0; upper-jaw length 17.7; lower-jaw length 16.5.
Size. The largest specimen is a mature male measured 439 mm TL.
Etymology. The specific name is from the Greek melano, black and stomus, a mouth, in refer to the black mouth.
Distribution. Known from the type series collected from eastern Taiwan off three localities, Changbin, Shihtiping and Shuilien at depth about 300 m.
description: Published as part of Huang, Jian-Fu, Ho, Hsuan-Ching, Chen, Hong-Ming & Chan, Tin-Yam, 2022, A new species of the congrid eel genus Bathycongrus (Order Anguilliformes) from eastern Taiwan, pp. 78-86 in Zootaxa 5189 (1) on pages 79-83, DOI: 10.11646/zootaxa.5189.1.10, http://zenodo.org/record/7119260