Two new snake eels (Anguilliformes, Ophichthidae, Ophichthus) from Viet Nam, with redescriptions of O.macrochir (Bleeker) and O.rutidoderma (Bleeker)

Two new extremely elongate snake eel of the genus Ophichthus are described based on specimens collected from Vietnamese waters. Ophichthuscuulongensis Vo, Hibino & Ho, sp. nov. is distinguished from its congeners by having the dorsal-fin origin slightly behind the pectoral-fin tip, mean vertebral formula 14-63-202, range 12-17/60-64/199-207; teeth on jaws biserial to triserial; dorsal body dark brown, ventral body pale, anal fin initially white but changing to darker towards its tip. Ophichthusnguyenorum Vo, Hibino & Ho, sp. nov. is distinguished by having a snout rather pointed but the occipital convex (duck-shaped); body with numerous longitudinal wrinkles, weak on posterior abdomen; dorsal-fin origin slightly behind the pectoral-fin tip; one row of teeth on the maxilla anteriorly but increasing posteriorly; two rows on the lower jaw; all teeth small; body dark, usually including abdomen; dorsal fin darker with dark margin; anal fin initially pale but changing to darker towards tip; mean vertebral formula: 15-62-192, range 13-17/61-64/190-196. Descriptions of two related species, O.macrochir (Bleeker, 1852) and O.rutidoderma (Bleeker, 1852), are provided with updated morphological data.