Etmopterus samadiae, White, William T., Ebert, David A., Mana, Ralph R. & Corrigan, Shannon, 2017
White, William T., Ebert, David A., Mana, Ralph R. & Corrigan, Shannon, 2017, Etmopterus samadiae n. sp., a new lanternshark (Squaliformes: Etmopteridae) from Papua New Guinea, Zootaxa 4244 (3), pp. 339-354: 340-349
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Etmopterus samadiae , new species
Etmopterus sp.— Fricke et al., 2014: 14 (Madang)
Paratypes. 9 specimens: ASIZ P.73777, adult male 230 mm TL, ASIZ P.73778, female 188 mm TL, ASIZ P.73765, pregnant female 277 mm TL, off Lae , Huon Gulf, Morobe Province, Papua New Guinea, 06°51.841' S, 147°04.672' E, 395–406 m depth, 22 Aug 2010GoogleMaps ; NTUM 10313 (tissue accession GN 17195), female 269 mm TL, northern Cape King William , Morobe Province, Papua New Guinea, 06°00' S, 147°38' E, 785 m depth, 10 Dec 2012GoogleMaps ; NTUM 10314 (tissue accession GN 17197), female 258 mm TL, Astrolabe Bay , Madang, Papua New Guinea, 05°22' S, 145°48' E, 420–490 m depth, 14 Dec 2012GoogleMaps ; NTUM 10315 (tissue accession GN 17198), female 154 mm TL, Astrolabe Bay , Madang, Papua New Guinea, 05°22' S, 145°48' E, 340–385 m depth, 14 Dec 2012GoogleMaps ; NTUM 10316 (3 specimens; tissue accessions GN 17210–2), female 177 mm TL, subadult male 201 mm TL, female 228 mm TL, west of Kairiru Island , East Sepik, Papua New Guinea, 03°19' S, 143°27' E, 422–425 m depth, 19 Dec 2012GoogleMaps .
Diagnosis. Etmopterus samadiae is a relatively small, slender, species of linear –denticled Etmopterus that can be separated from its closest congeners within the E. lucifer clade by a combination of characteristics including the length of its anterior flank markings being slightly shorter than its posterior branch, long caudal base marking, and irregular and variable number of black, horizontal, dash-like marks on sides of body. The new species is morphologically and genetically (based on the NADH 2 marker) closest to E. brachyurus , but differs from this species in having a shorter posterior caudal marking (2.8–4.4 vs. 4.2–6.1% TL), a longer caudal base marking (10.6–14.1 vs. 7.0–7.8% TL), and flank marking with a slightly shorter posterior branch (9.1–11.2 vs. 11.4–12.6% TL).
Description. Values expressed as a percentage of total length (TL) for the holotype, followed by the range of values for 9 paratypes ( Table 1).
Body fusiform, trunk sub-cylindrical ( Fig. 1View FIGURE 1), width 1.1 (0.7–1.7) in trunk height; head sub-conical, long, 21.3 (20.6–23.7)% TL, slightly depressed, height 0.7 (0.5–0.8) times width. Snout moderately long, conical in lateral view, in dorsal view triangular –shaped becoming rounded at snout –tip ( Fig. 3View FIGURE 3), head width 8.2 (9.8–11.8)% TL. Eyes oval-shape, large, orbit length 3.8 (3.0–3.7) in head and 2.6 (2.0–3.3) times orbit height; orbits with anterior and posterior notches; moderately spaced, inter –orbital space 1.2 (1.2–1.5) in width of head and orbit length 1.2 (1.1–1.4) times in inter –orbital distance. Spiracles small, semi-circular, greatest diameter 0.9 (1.4–2.5)% TL, 6.1 (2.7–4.0) times orbit length, distance to eye 2.9 (1.4–2.6)% TL, eye –spiracle length 0.7 (1.0–1.9) in orbit height. Nostrils large, oblique, length almost equal to internarial width, less than orbit length; anterior nasal flap well developed, triangular, anterior tip extending across nasal opening, length 1.0 (0.5–0.9) times spiracle length. Gill openings small, narrow, slightly oblique, in horizontal series, subequal in height, inter-gill length 4.9 (3.0–4.7)% TL. Mouth broad, length 3.4 (3.3–4.8) times in width, slightly arched, width 0.8 (0.7–0.9) times preoral length.
Teeth dissimilar in upper and lower jaw ( Fig. 4View FIGURE 4); upper teeth multicuspid in three functional series, functional teeth in lower jaw unicuspid in single series; multicuspid upper teeth small, upright, with strong central cusp flanked by 2 or 3 lateral cusplets on each side, decreasing in size distally; teeth in lower jaw fused into single row, blade-like, cusp oblique. Tooth count in first row of upper jaw 33 (27–28) and in first row of lower jaw 35 (28–31).
First dorsal fin small, rounded at apex, length of first dorsal fin 8.6 (8.5–9.9)% TL, origin just anterior to pectoral-fin free rear tip; fin base insertion well anterior of pelvic-fin origin; pre –first dorsal fin length 1.3 (1.4–1.8) times inter –dorsal distance; first dorsal –fin spine straight, short, 1.6 (1.3–2.0) times height of first dorsal fin, located over pectoral fin rear margin. Second dorsal fin conspicuously larger, more erect than first dorsal fin, length of first dorsal fin 0.6 (0.6–0.8) times second dorsal fin, height of first dorsal fin 0.4 (0.5–0.7) times second dorsal fin; apex sub –angular, posterior margin concave, free rear tip elongated, length 13.2 (12.2–13.6)% TL, pre –second dorsal length 2.5 (2.6–3.1) times inter –dorsal distance; second dorsal –fin spine large, height slightly taller than fin, curved near tip towards fin apex; origin posterior to insertion of pelvic fins, over pelvic fin free rear tips. Interspace between first and second dorsal fins 1.0 (0.8–1.0) times pre –pectoral length.
Pectoral fins relatively large, length 9.4 (10.1–11.3)% TL, subangular at free rear tips, base 2.0 (1.7–2.1) times in anterior margin, posterior margin nearly straight. Caudal peduncle relatively long, dorsal-caudal space 16.1 (13.6–15.3)% TL, height slightly greater than width, rounded, and tapering posteriorly. Caudal fin elongate, subequal to head length, terminal lobe distinct; length of lower preventral caudal fin margin less than one-half upper caudal fin margin.
Holotype Paratypes NTUM n = 4 n = 4
Min. Max. 10318 Min. Max. Min. Max. Dermal denticles hook-like, posteriorly directed rearwards; organized in distinct rows laterally, characteristic of E. lucifer clade members ( Fig. 5View FIGURE 5, 6View FIGURE 6). Distance between lateral rows mostly consistent along length, decreasing only very slightly towards caudal peduncle. Flank mark area denticles more dense and pointed ventrally.
Luminescent markings distinct, intricate ( Fig. 7View FIGURE 7 D); ventral head surface markings blackish, starting from almost at snout tip, extending to level of nostrils and orbits at just below level of anterior notch, then extending straight from just below posterior eye notch towards gill slits, weakly demarcated from belly marking by a weak band of transverse dermal folds across throat extending from below lower edges of first three gill openings on either side. Head dorsal surface photophore pattern as follows: a single midline along back originating at level of first gill slits extending posteriorly to caudal –fin origin; scattered photophores on paler fontanelle area of central head and also on paler area above orbits (as short dashes in some paratypes).
Belly marking originates behind mouth on posterior portion of transverse dermal folds and extends ventrally along pectoral fin bases extending upwards to level with fin origin and upper edges of gill slits, and posteriorly to pelvic fin bases; ventral surface of pectoral fin very dark along lower base and upper base where ceratotrichia originate, bisected by distinct lighter to white band or blotch forming a two –prong fork pattern; margin on lateral trunk (pectoral –pelvic space) very clearly defined, line extending from rear margin of pectoral –fin base nearly to pelvic –fin insertion except for paler area at pelvic-fin origin; dark ventral belly surface continuous onto caudal peduncle to about lower caudal fin origin.
Flank markings well defined ( Fig. 7View FIGURE 7 d), consisting of both an anterior and posterior branch; anterior branch relatively short, length 10.3 (8.2–10.5)% TL, slender, nearly straight, extending well anterior to pelvic –fin origin; posterior branch straight, slightly thicker, width at level of base end of second dorsal fin 0.6 (0.5–0.8)% TL, slightly longer than anterior branch (shorter than anterior branch in paratype ASIZ P.73777), length 11.2 (9.1– 10.8)% TL, extending to just anterior to second dorsal-fin free rear tip but well posterior to second dorsal-fin insertion; base of flank marking wide, origin slightly posterior to pelvic-fin insertion. Ventral caudal base marking distinct, short, length about equal to base of flank marking, not extending as a saddle on to caudal peduncle, anterior finger very short, posterior finger long, total length (including base) 11.4 (10.6–14.1)% TL. No central caudal marking. Posterior caudal fin marking very narrow, its length 3.2 (2.8–4.4) % TL.
Vertebral counts: total counts 80 (80–86), total precaudal counts 55 (55–59); monospondylous 34 (36–37); diplospondylous precaudal 21 (19–22); caudal 25 (25–27).
Coloration. In life, greyish to silvery black dorsally and laterally on body, becoming dark black ventrally; transition between lateral and ventral surfaces well demarcated by a paler lateral stripe below the flank markings in most specimens (less distinct in holotype and some paratypes). Dorsal midline with a broad, pale stripe originating just posterior to midpoint of inter-spiracle space, extending to first dorsal fin origin, continuing between dorsal fins, and from second dorsal fin insertion to upper caudal fin origin ( Fig. 2View FIGURE 2); most prominent anterior to first dorsal fin and between dorsal fins, less prominent along upper caudal peduncle; a single row of dark photophores extending along middle of white dorsal stripe. Body with variable number and arrangement of short, horizontal, dash-like black markings ( Fig. 8View FIGURE 8); most numerous in paratype NTUM 10314 ( Fig. 8View FIGURE 8). Pectoral and pelvic fins dark at base and along anterior fin edge, becoming translucent to white on remainder of fins. Dorsal fins dark at base and along anterior edges, becoming translucent to white on remainder of fins. Black lateral flank markings demarcated by surrounding lighter colored lateral flanks (not sharply demarcated in most preserved specimens). Paler colored flank area on lateral surface between pectoral and pelvic fins sharply demarcates lateral and ventral surfaces; ventral surface black. Caudal fin with a distinct, large dark blotch centrally, occupying the area between the posterior finger of the caudal base marking and the upper caudal marking; posterior margin dark. Ventral surface mostly dark black around mouth, belly, and with a dark stripe between pelvic fin insertions and caudal origin; snout not distinctly paler than mouth. After preservation coloration similar but with paler markings often less obvious and coloration becoming a light or dark brown; dorsal median pale stripe and whitish flank area and black lateral flank markings less prominent but still distinct in most cases; dark blotch on central caudal fin obvious and darker pores extending laterally on body still clearly visible under microscope.
Molecular analysis. The analysis of the NADH 2 data confirms that Etmopterus samadiae belongs in the E. lucifer clade and represents a monophyletic lineage that is distinct from, but most closely related to Etmopterus brachyurus ( Fig. 9View FIGURE 9). It should be noted that this inference is based on a single mitochondrial marker. Inclusion of multiple nuclear markers could affect the presented inference.
Size. Specimens examined ranged in size from 154 to 277 mm TL. A 277 mm TL female ( ASIZ P.73765) was found to be pregnant (embryo caudal fin visible in cloaca) and two males 230 ( ASIZ P.73777) and 265 mm TL ( NTUM 10078) were determined to be mature.
Distribution. The new species is known from off the northern Papua New Guinea mainland, from west of Kairiru Island in East Sepik Province to off Lae in the Huon Gulf (Morobe Province) and at a depth range of 340 to 785 m ( Fig. 10View FIGURE 10).
Etymology. The species is named after Dr Sarah Samadi ( MNHN) who was one of the key principal investigators of the 2010 and 2012 MNHN expeditions in Papua New Guinea from which all the type specimens were obtained. The proposed English common name is Papuan Lanternshark.
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