Etmopterus joungi Knuckey, Ebert & Burgess, 2011
Shortfin smooth lanternshark
Etmopterus joungi
photo by Ebert, D.A.

Family:  Etmopteridae (Lantern sharks)
Max. size:  40.6 cm TL (male/unsexed); 45.6 cm TL (female)
Environment:  pelagic-oceanic; marine; depth range - 300 m
Distribution:  Northwest Pacific: Taiwan.
Diagnosis:  This species is distinguished by the following characters: short preoral snout 8.0% TL (8.2-8.7); broad and strongly arched mouth; upper teeth differ from lower teeth with each tooth in first functional row with single median cusp and flanked by one or two lateral cusplets on either side; lower teeth in single series, forming blade-like edge with slender, non-erect cusps; relatively short head, 15.9% TL (15.3-16.0); dermal denticles truncate, low, with block-like crowns, irregularly arranged over majority of body, extending onto dorsal fins; pectoral to pelvic fin space large, 29.0% TL (25.3-27.30); very narrow pectoral fins, posterior portion square-shaped, posterior margin acutely angular at anterior and inner margins, with no expanded corners of fins; second dorsal fin located relatively posteriorly along body, second dorsal fin spine long and strongly recurved, 0.5 (0.3-0.5) into dorsal fin height; interdorsal space about three times distance between first dorsal fin spine origin and pectoral fins; inconspicuous suprapelvic flank marking lacking posterior branch; dorsal caudal fin margin short, 15.4% TL (15.3-19.4); posterior end of lateral line becoming open groove, with the ventral edge darkly colored; caudal fin short; monospondylous vertebrae 48 (38-41), diplospondylous vertebrae 17 (21-24), dorso-caudal vertebrae 24 (22-25), and total vertebrae 89 (84-88); spiral valve with 11 turns; color in life dusky grey dorsally, black to dark grey ventrally (Ref. 86885). Description: This species is similar to other species of the 'Etmopterus pusillus group' in having the following characters: concave, flattened dermal denticles scattered irregularly across the body; lateral line that ends in an open groove; no suprapelvic flank markings at the posterior branch; and a relatively cylindrical body. It also differs from its congeners based on the following characteristics: gill slit height, tooth morphology, fin size and shape, interdorsal space and suprapelvic flank markings; it has a shorter preoral length and the gill slit height does not vary much compared to other members of the "E. pusillus group"; teeth in lower jaw are slender, with relatively oblique cusps when compared to those of its congeners; pectoral fins are more squared posteriorly and the caudal fin is shorter than the other members of the group. The pectoral axil to first dorsal fin origin measurement of E. joungi fits into the interdorsal space about three times (Ref. 86885).
Biology:  Occurs along the upper continental slope and caught by bottom trawl at a depth greater than 300m. Sexual maturity in males likely achieved between 31.9 and 40.6 cm TL, and in females, larger than 45.6 cm TL. A cymothiod isopod Elthusa raynaudi was found attached to the roof of the mouth of the holotype (normally occurs in the gill chambers of fishes) (Ref. 86885).
IUCN Red List Status: Least Concern (LC); Date assessed: 02 September 2019 Ref. (124695)
Threat to humans:  harmless
Country info:   

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