Hymenocephalus nascens Gilbert & Hubbs, 1920
Nascent membranehead
photo by Graham, K.

Family:  Macrouridae (Grenadiers or rattails)
Max. size:  18.2 cm TL (male/unsexed)
Environment:  benthopelagic; marine; depth range 366 - 1000 m
Distribution:  Western Central Pacific: South China Sea off Hong Kong, through Philippines and Indonesia, off northern Australia, to New Caledonia and New Zealand.
Diagnosis:  Dorsal spines (total): 2-2. This species is distinguished by the following characters: pelvic rays usually 12-14 (elsewhere 11-13); total gill-rakers first arch (outer/inner) 17-22/23-28, second arch 22-28/22-26; no chin barbel; snout length 22-31% HL; orbit diameter 29-40% HL; suborbital width 10-14%HL, interorbital width 24-29%HL; most of the orbit, upper surface of snout, sides of head and trunk silvery or pale, ventral aspects of heed and trunk black; a prominent midlateral stripe of silvery (when fresh) or brownish (preserved) pigment running along trunk and tail (Ref. 97189). Additional distinguishing characteristics: pectoral fin rays 13-16; projecting snout, 20-26% HL; infraorbital width 11-16% HL; moderately long preopercular supporter, with obtuse angle at rear margin, 4-9% HL; ventral striae reaching to ½ distance from pelvic fin bases to periproct; otolith has moderately high predorsal lobe, with colliculi separated, closely placed across collum with a tendency to joining in large individuals, terminating at some distance from anterior and posterior rims of otolith; otolith length to height (OL:OH), 1.1-1.2; total colliculum length to pseudocolliculum length (TCL:PCL), 1.8-2.4 (Ref. 98298).
Biology:  A benthic species found on the continental slope (Ref. 75154). Maximum depth from Ref. 106682.
IUCN Red List Status: Not Evaluated (N.E.) Ref. (130435)
Threat to humans:  harmless
Country info:  Collected during the Hearst Expedition 2011 done off Batangas and Mindoro, off SW Luzon (Ref. 95664); also collected off Zamboanga (Ref. 98298). Also Ref. 35908.


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