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Author: Smith and Radcliffe, 1912

Field Marks:
Two spined dorsal fins, no anal fin, bladelike unicuspidate teeth in lower jaw and teeth with cusps and cusplets in upper jaw, conspicuous lines of denticles on body, slender body, prominent ventral and very long tail markings.

Diagnostic Features:
A very slender-bodied lanternshark with a long tail, distance from pelvic insertions to ventral caudal origin about as long as from tip of snout to pectoral origins, about 1.2 times distance between pectoral and pelvic bases, and slightly greater than interdorsal space; distance between pectoral and pelvic bases short in adults, less than head length; distance from snout tip to first dorsal spine about equal to distance from first dorsal spine to second dorsal insertion, first dorsal base considerably closer to pectoral bases than pelvics. Head width about equal to preoral snout. Prespiracular length slightly greater than distance from spiracles to pectoral origins; gill openings very short, about as wide as spiracle, 1/3 eye length or less; upper teeth with 3 pairs of cusplets. Origin of first dorsal-fin above inner margins of pectoral fins. Interdorsal space short, slightly less than distance from snout tip to pectoral origins; second dorsal fin much larger than first and about twice its area; distance between second dorsal base and upper caudal origin about 1.4 in interdorsal space; caudal fin long and slenderz length of dorsal caudal margin about equal to distance from snout tip to pectoral origins. Lateral trunk denticles with slender, hooked conical crowns, arranged in prominent regular longitudinal rows on dorsal surface of head, sides of body and tail that give the shark an etched, engraved appearance; snout largely covered with denticles; no rows of greatly enlarged denticles on flanks above pectoral fins. Distal margins of fins largely covered with skin, not fringed with naked ceratotrichia. Colour brown above, with underside of snout and abdomen abruptly black, with an extremely narrow elongated black mark running above, in front and behind pelvic fins, and other elongated black marks at caudal fin base and along its axis.

Geographical Distribution:
Western Pacific: Philippines, and probably elsewhere in the western Pacific.

Habitat and Biology:
A little-known lanternshark, found near the bottom in the Philippine Islands at 481 m depth.

Size:
Maximum total length over 22.7 cm (male holotype with damaged caudal fin, probably at least 24 cm long with complete tail).

Interest to Fisheries:
None at present.

Remarks:
This lanternshark is close to E. lucifer but has usually been recognized as a valid species on the primary character of its shorter caudal fin (Fowler, 1941; Bigelow and Schroeder, 1957). However, examination and radiography of the holotype convinced me that this is based on an anomaly. Apparently this specimen had its caudal fin damaged in life; the terminal lobe was apparently severed (perhaps by a predator), and the caudal fin was partially regenerated distal to its truncated vertebral column to form a false terminal lobe. This species may be a synonym of E. lucifer but is tentatively recognized here. As indicated by the illustrations of this species and E. lucifer (both made from holotypes, with the caudal fin of E. brachyurus restored from other Philippine examples of the species), E. brachyurus may be a slenderer shark with a longer interdorsal space, shorter head, smaller second dorsal fin, and longer posterior branch on its black tail marking. It is uncertain at present if all these differences are valid. If so, some records of E. lucifer may be based on E. brachyurus.

Type material:
Holotype: U.S. National Museum of Natural History, USNM 70257, 227+ mm adult male. Type Locality: Jolo Island, Philippines, 481 m depth.

Shorttail lanternshark (Etmopterus brachyurus)