Rostroconger macrouriceps, Smith, 2018

Smith, David G., 2018, A new genus and species of congrid eel from the Philippines (Anguillliformes: Congridae: Bathymyrinae), Zootaxa 4454 (1), pp. 78-83 : 79-82

Rostroconger macrouriceps sp. nov.

Figures 1–2 .

Holotype. ASIZP 68072 (241 mm TL), Aurora, Luzon , Philippines, 15°11’04.2”N, 121°34’43.2”E, 28 May 2007, 244– 296 m, French type beam trawl, coll. Y.- C. Liao & K.- T. Shao.

Diagnosis. That of the genus.

Description. Morphometric and meristic characters, length in mm with proportions in parentheses. TL 241 mm; preanal 98 (40.7 % TL), predorsal 45.3 (18.8 % TL), head 38.4 (15.9 % TL), trunk 59.6 (24.7% TL), tail 143 (59.4% TL), depth at anus 12.8 (5.3 % TL), snout 8.9 (23.2 % HL), eye 7.8 (20.3 % HL), snout-rictus 16.0 (41.7 % HL), gill opening 3.8 (9.9 % HL), interbranchial 9.5 (24.7 % HL), pectoral fin 17.3 (45.1 % HL). Preanal LL pores 39, predorsal LL pores 11, prepectoral LL pores 6, POM pores 5, IO pores 2, SO pores 4, ST pores 0. Pectoral-fin rays 13. Vertebrae: predorsal 12, preanal 45, precaudal ca. 63, total 143; myorhabdoi present.

Body moderately stout, tail distinctly longer than head and trunk, relatively broad and bluntly rounded, its tip stiffened ( Fig. 1a ). Dorsal fin beginning slightly behind midpoint of appressed pectoral fin; dorsal and anal fins continuous with caudal fin. Caudal fin well developed, not noticeably shortened, but with basal part of central rays reinforced and resistant to being bent. Pectoral fin well developed, its base oriented vertically. Gill opening moderately small, oriented nearly vertically, with a slight anterodorsal to posteroventral incline, its upper corner at middle of pectoral-fin base; distance between ventral corners of right and left gill openings separated across ventral midline by a distance slightly more than twice their length.

Head moderate in length and depth, snout distinctly acute due to bony rostrum, which is somewhat flattened in a dorsoventral direction, giving the head a macrourid-like appearance ( Fig. 1b ). Rictus at about level of posterior margin of eye. Upper and lower labial flanges well developed, the upper flange extending forward along rostrum to anterior nostril. Bony rostrum extending forward from vomerine tooth patch, forming a distinct naked floor on underside of rostrum; inclined slightly upward in lateral view ( Fig. 1c ). Top of head covered with small dermal bumps.

Anterior nostril on underside of snout, behind its tip, tubular, opening in an anteroventral direction. Posterior nostril opening ventrally as a slit in edge of groove separating surface of snout from upper labial flange, at a point slightly closer to eye than to tip of snout ( Figs 1b , 2a, 2b ).

Head pores small, each at the end of a blunt papilla ( Figs. 2a, b ). Four SO pores; first two located on underside of snout, the first very small, just behind tip of snout; the second slightly larger, just behind first and adjacent to base of anterior nostril; third on top of snout, above level of anterior nostril; fourth on side of snout just above posterior nostril; fifth and sixth pores absent. Three IO pores; the first just behind base of anterior nostril; the second above posterior end of labial flange, slightly behind mid-eye level, visible on right side only; the third behind and slightly above level of rictus on each side; no other IO pores visible. Five pores visible on mandibular portion of POM canal, none apparent on preopercular section. ST pores absent. Lateral line well developed on body, pores easily visible as small spots; 11 predorsal, 6 prepectoral, 39 preanal.

Teeth conical, relatively small ( Fig. 2c ). Intermaxillary teeth apparently in two sections, one at base of rostrum continuous with and somewhat larger than maxillary teeth, and the other at anterior tip of rostrum, the two sections separated by a long toothless gap. Maxillary teeth uniserial, compressed and blade-like, closely set, forming a cutting edge, the tips of most curved posteriorly, but in posteriormost teeth the tips curved anteriorly. Vomerine teeth somewhat enlarged, arranged in a short, rounded patch, flanked on either side by the maxillary teeth, and partially separated from intermaxillary patch with a few teeth in between. Mandibular teeth uniserial, similar in form and arrangement to maxillary teeth.

Color in ethanol light to medium brown, belly somewhat paler. Dorsal fin and most of caudal fin pale; anal fin black-edged at posterior end, the black edge extending onto ventral margin of caudal fin. Color in life similar.

Etymology. From Macrouridae , a family of gadiform fishes, and Latin ceps, head, in reference to the macrourid-like appearance of the bony rostrum at the tip of the snout.

Distribution. Known only from the type locality off the east coast of Luzon, Philippines.

Figures

FIGURE 1. Rostroconger macrouriceps sp. nov., holotype, 241 mm TL. A. Lateral view of fresh caught specimen. B. Lateral view of head, line indicates position of posterior nostril. C. Lateral view of tail. D. Radiograph of head with bony rostrum.

FIGURE 2. Rostroconger macrouriceps sp. nov., from the holotype. A. Lateral view of head showing position of nostrils and pores. AN, anterior nostril; PN, posterior nostril. B. Ventral view of head, showing position of nostril and pores. C. Tooth pattern of upper jaw.