Etmopterus schmidti Dolganov, 1986

Etmopterus schmidti Dolganov, 1986

( Figs 4 D View Figure 4 , 5 D View Figure 5 , 13 B, D View Figure 13 , 14 B View Figure 14 , 15; File S 2: Table S 3 View Figure 15 )

Etmopterus schmidti Dolganov, 1986: 150, fig. 1 (original description in Russian; holotype in the Russian Academy of Sciences, Zoological Institute, Saint Petersburg ZIN 22362, Sagami Sea, Japan; 1 paratype); Weigmann (2016): 894, 896 (listed).

Etmopterus lucifer View in CoL (not Jordan and Snyder 1902): Chen (1963): 84, 85, fig. 26 (brief description, reidentification based on illustration); Kato et al. (1967): 12, fig. 15 (brief description; reidentification based on the illustration).

Etmopterus molleri View in CoL (not Whitley, 1939): Yamakawa et al. (1986): 203, 197–207, fig. 6 C (revision of the E. lucifer View in CoL group in Japan; brief description; listed in key); Joung and Chen (1992): 22, fig. 5 (new record in Taiwanese waters, description on Taiwanese specimens); Compagno (1999): 473 (listed); Nakabo (2000): 146 (listed in key), Compagno in Randall and Lim (2000): 580 (listed); Nakabo (2002): 146 (listed in key); Schaaf-Da Silva and Ebert (2006): 62 (listed in key); Weigmann 2016: 896 (listed, northwest Pacific).

Etmopterus cf. molleri View in CoL : Ebert et al. (2013): 294 (listed); Ng et al. (2024 b): 181, fig. 5 E.

Materials examined.

40 specimens. Paralectotypes of Etmopterus lucifer (see above): CAS - SU 7832 (3 of 4 specimens), females 258–329 mm TL, off Misaki, Japan, 35°14'N, 139°37'E, depth and date unknown; USNM 50728 , mature male 273 mm TL, off Sagami Bay, Japan, depth unknown, 1900. Non-types: CAS 11225 (2 specimens), mature female 263–301 mm TL; off Misaki, Japan, 35°14'N, 139°36'E, depth and date unknown; CAS - SU 23779 , off Sagami, Japan, 34°58'N, 139°36'E, depth unknown, 12 March 1906; EBFS-NG 00030 , off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 25 March 2022; EBFS-NG 00031 , off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 15 December 2021; EBFS-NG 00032 ; EBFS-NG 00033 , mature female 309 mm TL, EBFS-NG 00034 , mature female 305 mm TL, EBFS-NG 00035 , mature female 308 mm TL, South China Sea, ca. 19°N, 114°E, ca. 500 m, 19 February 2021; EBFS-NG 00036 , mature female 317 mm TL, off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 25 March 2022; EBFS-NG 00038 mature male 307 mm TL, EBFS-NG 00039 , mature female 337 mm TL, South China Sea, ca. 19°N, 114°E, ca. 500 m, 19 February 2021; EBFS-NG 00040 , mature female 321 mm TL, EBFS-NG 00041 , off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 19 February 2021; EBFS-NG 00042 , off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 23 December 2021; EBFS-NG 00079 ; EBFS-NG 00080 ; EBFS-NG 00081 ; EBFS-NG 00082 , juvenile female 255 mm TL, EBFS-NG 00083 , juvenile female 310 mm TL, EBFS-NG 00084 , mature female 316 mm TL, EBFS-NG 00085 , juvenile female 293 mm TL, EBFS-NG 00086 , mature female 321 mm TL; EBFS-NG 00087 , mature female 308 mm TL, EBFS-NG 00088 , mature female 338 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 13 May 2022; EBFS-NG 00090 ; EBFS-NG 00091 ; EBFS-NG 00092 ; EBFS-NG 00093 ; EBFS-NG 00094 ; EBFS-NG 00095 , South China Sea, ca. 19°N, 114°E, ca. 500 m, 25 April 2022; EBFS-NG 00096 , embryos from EBFS-NG 00088 (3 specimens), off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 13 May 2022; EBFS-NG 00102 ; EBFS-NG 00103 ; EBFS-NG 00104 ; South China Sea, ca. 19°N, 114°E, ca. 500 m, 25 April 2022, coll. C. - H. Lin; EBFS-NG 00112 ; EBFS-NG 00113 , off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 25 April 2022; EBFS-NG 00120 , off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 18 May 2022; EBFS-NG 00133 , pregnant female 304 mm TL, EBFS-NG 00134 , mature female 333 mm TL, EBFS-NG 00135 , immature male 267 mm TL, EBFS-NG 00136 , immature male 286 mm TL, EBFS-NG 00137 , embryos from EBFS-NG 00133 (3 specimens), off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 30 May 2022; EBFS-NG 00158 , mature female 349 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 21 June 2022; EBFS-NG 00283 , mature male 272 mm TL, off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 9 November 2022; HUMZ 222742 , female 342 mm TL, off Kochi, Japan, 250–350 m, 17 February 2014.

Diagnosis.

A moderately small Etmopterus of the E. lucifer group showing typically elongated anterior and posterior branches of lateral flank markings. It differs from other members by the following combination of characters: hook-like dermal denticles not overlapping each other, in well-defined rows; the origin of second dorsal fin well posterior to flank-marking base origin; infracaudal marking not connected with caudal-fin base marking through luminous lines; posterior caudal-fin marking long, length 20.3–34.4 % caudal-fin length; caudal-fin upper lobe translucent; caudal-base marking bifurcated after caudal-fin origin; and ventral pectoral marking curved.

Redescription.

Morphometric information is provided in File S 2 (Table S 3). Proportional measurements and tooth counts are provided as ranges for the non-types. Tooth counts for the holotype (data obtained from Dolganov 1986) are provided in parentheses.

Trunk sub-cylindrical, width narrower than to slightly wider than height; abdomen usually longer than lower caudal peduncle, often shorter in mature males; head subconical, moderately depressed. Snout quite short (Fig. 15 View Figure 15 ), preorbital length 19.7–29.6 % head length; snout narrowly rounded in both lateral and dorsal view. Eye oval. Spiracle bean-shaped. Gill openings short, a little bit oblique. Mouth broad, length 50.2–97.4 % width, rather arched. Preoral length relatively short, length 32.7–45.4 % head length.

Teeth dissimilar in upper and lower jaw, having ontogenetic change and sexual dimorphism, as in the congeners; multicuspid upper teeth in three functional series; unicuspid lower teeth in three series, one functional; lower teeth blade-like, strongly oblique. No symphyseal and intermediate teeth. Upper teeth cusp rather thick; immature males and both immature and mature females with 1–2 cusplets on each side of the upper teeth (rarely 3), while mature males having 3–4 cusplets (Fig. 3 D View Figure 3 ); longest cusplet length about two-third of the cusp in mature individuals; cusp and cusplets of upper teeth slender, lower teeth of mature individuals not erected. Tooth count of upper jaw 24–30 (28), lower jaw 32–42 (38), total count 57–70 (66).

D 1 small, with a broadly round apex, origin usually slightly posterior a vertical line through P 1 free rear tip. D 2 larger than D 1, apex broadly angular, posterior margin especially concave, free rear tip moderately elongated; D 2 spine long and variously curved. P 1 with moderate size, with angular free rear tips, base narrow, posterior margin slightly concave. P 2 triangular. Clasper of mature males fairly long. Caudal fin elongate, caudal fork not especially developed; terminal lobe broad.

Dermal denticles hook-like, rather low, slightly reclined backwards, widely-spaced, not overlapping, giving a rough texture of the skin, in defined rows (Fig. 4 D View Figure 4 ); distribution of denticles on underside of snout vary, usually fully covered with denticles except for a broad area around mouth, often with bare batches on the internarial area; underside of gill slits fully covered with denticles, rarely with small bare patch; Inner margin of fins with a broad naked area; denticles present on fin bases, but almost absent on fins (Fig. 5 D View Figure 5 ).

Body lateral side with numerous dot-like markings; head dorsal surface with scattered dot-like markings; dorsal contour of the body with single line of dot-like markings, extending mid-dorsally from about the level of anterior fontanelle to D 2 origin; ventral pectoral marking elongated and arched, tip not reaching P 1 insertion. Flank markings well defined, with elongated anterior and posterior branch; anterior flank marking slender, slightly curved, extending above P 2 origin; posterior flank marking straight, not much thicker, usually longer than anterior flank marking; anterior flank marking length 59.5–101.7 % posterior flank marking length, usually with blunt tip; posterior flank marking often extending beyond D 2 free rear tip; flank marking base rather narrow, origin well anterior to D 2 origin. Infracaudal marking prominent, extending from flank marking base to about the same level of posterior flank marking tip, not connecting to caudal-base marking by a pair of lines; caudal-base marking broad, with moderately thick extension, bifurcated after lower caudal-fin origin, leaving black area at the caudal-fin origin, with bluntly rounded tip, length 21.6–42.1 % caudal-fin length (Fig. 13 B, D View Figure 13 ). Posterior caudal-fin marking moderately long, its length 20.4–34.4 % caudal-fin length.

Coloration.

When fresh, body shiny to bluish grey, sometimes dark purple; much darker ventrally; transition between lateral and ventral sides strongly demarcated. Dorsal midline with pale stripe, not especially distinct when fresh; Fins, except caudal fin, generally translucent, with darker anterior margins and bases. Caudal-fin dorsal and postventral margins translucent (Fig. 14 B View Figure 14 ); dark blotch on mid-caudal fin prominent. Black blotch present between infracaudal marking and caudal-base marking. Caudal fin with distinct black tip on terminal margin and lower lobe.

After preservation, body coloration becoming dull grey, still demarcated from darker ventral side; dorsal margin of caudal fin sometimes darker.

Size.

Up to 368 mm TL and 330 mm TL for females and males ( Dolganov 1986), respectively. Smallest mature female 263 mm TL and male 272 mm TL, respectively.

Distribution.

Northwestern Pacific, from warm temperate waters off Japan to northern South China Sea, at depth 250– 500 m.

Nomenclatural discussion.

Etmopterus schmidti was described from Japan by Dolganov (1986). The nominal species was rarely discussed until Weigmann (2016), who regarded it as a junior synonym of either E. molleri and E. brachyurus . Unfortunately, we had no opportunity to examine the type series of E. schmidti physically. Yet, some characters of the holotype of E. schmidti ( ZIN 22362 ) judged from Fig. 15 A View Figure 15 , distinguish it from E. molleri and E. brachyurus . The holotype possesses a naked second dorsal-fin, a rather thick caudal-base marking, and the underside of the snout is fully covered with denticles, which allows clear distinction from E. brachyurus (second dorsal fin covered with denticles in specimens of similar sizes; caudal-base marking slender; underside of snout with a reverse ‘ W’ shaped naked area). Morphologically, the holotype of E. schmidti is very similar to E. molleri , but has the caudal-base marking bifurcated after the lower caudal-fin origin, leaving a small black area at the origin (vs. bifurcate before the origin, no black area in E. molleri ). The snout is also short relatively to the head length.

Specimens previously identified as ‘ E. molleri ’ or ‘ E. cf. molleri ’ from Japan, Taiwan and the northern South China Sea examined in the present study resemble E. schmidti morphologically. The genetic divergence of these specimens compared to E. molleri from the Southwestern Pacific is large, with an average 11.5 %. Based on these results, we formally resurrect E. schmidti here.

Remarks.

Fricke and Eschmeyer (2024) listed the catalog number of the paratype of E. schmidti (not examined in the present study) as ZIN 753. However, according to the original description ( Dolganov 1986) and personal communication with M Nazarkin (Russian Academy of Sciences, Zoological Institute, Saint Petersburg), the catalog number should be MT 753, which refers to Museum of TINRO, the Russian Federal Research Institute of Fisheries and Oceanography, Pacific Branch, Vladivostok.

Comparisons.

Etmopterus schmidti can be assigned to the E. lucifer group and is most similar to E. molleri (see also comparison of E. molleri ). Etmopterus schmidti shows further some similarities to the sympatric E. brachyurus , however, E. schmidti usually occurs in shallower waters (300–400 m, Ng pers. obs.). Apart from the characters mentioned above (see nomenclatural discussion), the tip of the caudal-fin base marking of E. schmidti is usually rounded, while the tip is pointed in E. brachyurus ; the posterior caudal-fin marking is usually longer in E. schmidti (20.4–34.4 vs. 10.9–21.2 % caudal-fin length in E. brachyurus ).