51 specimens. Holotype: NMNZ P.01951, immature male 330 mm TL, off south Kaikoura, New Zealand, 42°58'S, 173°40'E, 366 m, November 1955. Paratype: MCZ 39714, female 267 mm TL, off south Kaikoura, New Zealand, 42°50'S, 173°41'E, 180 m, February 1956. Non-types: AMS E.5530, female 355 mm TL, south of Gabo Island, southeastern Australia, 37°00'S, 149°54'E, 6 October 1914; AMS E.5531, female 301 mm TL, southeast of Gabo Island, southeastern Australia, 37°00'S, 150°00'E, 15 September 1914; AMS I.12820, mature male 403 mm TL, Great Australian Bight, southern Australia, 32°00'S, 129°28'E, 14 May 1913; AMS I.15994-003, female 346 mm TL, south of Eden, southeastern Australia, 37°43'S, 150°15'E, 30 July 1971; AMS I.20096-003, female 389 mm TL, southeast of Gabo Island, southeastern Australia, 37°38'S, 150°20'E, 30 November 1977, coll. K. Graham; AMS I.26000-009, female 422 mm TL, off Broken Bay, southeastern Australia, 33°30'S, 152°09'E, 12 February 1986, coll. K. Graham; AMS I.40290-003, juvenile male 206 mm TL, off Bermagui, southeastern Australia, 36°27'S, 150°18'E, 2 May 2000, coll. K. Graham; AMS I.42746-003 (3 specimens), mature males 388–402 mm TL, western Norfolk Ridge, Tasman Sea, 33°49'S, 167°03'E, 27 May 2003; AMS I.44903-001 (2 specimens), 323–363 mm TL, Taupo Seamount, Tasman Sea, 33°21'S, 156°07'E, 11 September 2009, coll. K. Graham; AMS I.44991-004 (4 specimens), 386–415 mm TL, north of Sydney closure, southeastern Australia, 33°39'S, 151°57'E, 15 September 2009, coll. K. Graham; AMS I.45667-013, mature female 432 mm TL, Ulladulla slope, southeastern Australia, 35°25'S, 150°51'E, 4 November 2011, coll. K. Graham; AMS I. 46064-001 (2 of 5 specimens), mature female 473–492 mm TL, Gascoyne Seamount, southeastern Australia, 36°10'S, 156°12'E, 11 June 2012, coll. K. Graham; CAS 218737 (2 specimens), 307–377 mm TL, Tasman Sea, 32°42'S, 162°34'E, 850–872 m, 25 May 2003; CSIRO H 2353-01, mature male 395 mm TL, northwest of Bunbury, western Australia, 32°52'S, 114°35'E, 517 m, 25 December 1989; CSIRO H 6042-13, female 472 mm TL, CSIRO H 6042-14, female 396 mm TL, CSIRO H 6042-15, female 420 mm TL, Lord Howe Rise, Tasman Sea, 32°41'S, 162°33'E, 855–874 m, 25 May 2003; CSIRO H 6044-09, immature male 209 mm TL, Lord Howe Rise, Tasman Sea, 34°01'S, 162°36'E, 812–818 m, 25 May 2003; CSIRO H 7051-14, female 451 mm TL, east of Wollongong, southeastern Australia, 34°18'S, 151°25'E, 440 m, 20 September 2009; CSIRO H 7052-5, immature male 287 mm TL; CSIRO H 7052-6, immature male 321 mm TL; CSIRO H 7052-7, female 333 mm TL; CSIRO H 7052-8, female 405 mm TL; CSIRO H 7052-9, female 388 mm TL; H 7052-10, female 386 mm TL; CSIRO H 7052-11, female 437 mm TL, northeastern Flinders Island, Tasman Sea, 39°34'S, 148°50'E, 450–570 m, 3 October 2009; CSIRO H 7059-03, female 406 mm TL; CSIRO H 7059-04, female 438 mm TL, east of Sydney, southeastern Australia, 33°40'S, 151°55'E, 530 m, 15 September 2009 ; CSIRO H 7174-01, juvenile male 383 mm TL, Lord Howe Rise, Tasman Sea, 34°05'S, 162°49'E, 560 m, 14 April 2003; CSIRO H 8866-01, female 391 mm TL, east of Eaglehawk Neck, Tasman Sea, 43°06'S, 148°15'E, 490 m, 16 February 2022; CSIRO H GT 6242, female 372 mm TL, presumably Australia; CSIRO T 598, mature male 371 mm TL, Great Australian Bight, southern Australia, 33°26'S, 129°05'E, 425–545 m, 4 June 1983; NMMZ P. 20893 (1 of 3 specimens), mature male 329 mm TL, southern Mernoo Bank, New Zealand, 43°44'S, 174°56'E, 423 m, 6 May 1987; NMMZ P. 27020, female 527 mm TL, Auckland Island Rise, New Zealand, 49°40'S, 168°25'E, 636–648 m, 20 October, 1990; NMNZ P.031152 (1 of 3 specimens), pregnant female 439 mm TL, northeastern Chatham Rise, New Zealand, 42°52'S, 178°09'E, 505–510 m, 26 May 1994; NMMZ P. 47326, female 461 mm TL, central southern Chatham Rise, New Zealand, 44°21'S, 178°15'W, 507–513 m, 31 December 2006; NMNZ P.054695, female 319 mm TL, southern Hokitika Canyon, New Zealand, 42°48'S, 169°51'E, 555 m, 4 August 2012; NMNZ P.057055, female 235 mm TL, Hokitika Canyon, New Zealand, 42°51'S, 170°31'E, 650 m, 27 July 2014; NMNZ P.058027, female 294 mm TL, east coast of North Island, New Zealand, 15 June 2015; NMMZ P. 60912, female 461 mm TL, Chatham Rise, New Zealand, 43°47'S, 178°18'W, 407–416 m, 27 July 2015. USNM 318374 (1 of 7 specimens), immature male 240 mm TL, Mernoo Bank, New Zealand, 300–800 m, May 1990.

A moderately large Etmopterus belonging to the E. lucifer group by having elongated anterior and posterior branches of lateral flank marking, and differing from other members by the following combination of characters: hook-like dermal denticles not overlapping each other, in well-defined rows; origin of second dorsal fin anterior to origin of base of flank-marking; infracaudal marking connected with caudal-fin base marking through pair of luminous lines; posterior caudal-fin marking long, length 30.2–46.5% caudal-fin length; and ventral pectoral marking strongly curved.

Morphometric information is provided in File S2 (Table 1). Proportional measurements and tooth counts are provided as ranges for the paratype and the non-types, followed by the holotype in parentheses. A precise tooth count of the lower jaw teeth is not possible in the holotype as several teeth are missing.

Trunk sub-cylindrical, body width narrower than to slightly wider than body height; abdomen longer than lower caudal peduncle; head subconical, slightly depressed. Snout moderately short (Fig. 2), narrowly rounded in lateral and dorsal view. Eye oval. Spiracle bean-shaped. Gill openings small, nearly straight. Mouth broad, very slightly arched.

Figure 2. 

Etmopterus abernethyi. A holotype, NMMZ P.01951, immature male 330 mm TL, off south Kaikoura, New Zealand B paratype, MCZ 39714, female 267 mm TL, off south Kaikoura, New Zealand (photo provided by MCZ, used with permission) C fresh specimen, CSIRO H 8866-01, female 391 mm TL, east of Eaglehawk Neck, Tasman Sea (photo provided by CSIRO Australian National Fish Collection, used with permission). Scale bars=20 mm.

Teeth dissimilar in upper and lower jaw, with strong ontogenetic change and sexual dimorphism; upper teeth multicuspid, in three functional series; in lower jaw unicuspid, in three series, one functional; lower teeth blade-like, with strongly oblique cusp. No distinctive symphyseal and intermediate teeth. Upper teeth central cusp rather thick; immature males and females with 1–2, rarely 3, cusplets on each side of the upper-teeth cusp, but mature males with 3–4 cusplets, rarely 2 (Fig. 3A); in mature individuals, longest cusplet length about two-third of the cusp in mature individuals; cusp and cusplets of upper teeth narrowly triangular, lower teeth of mature individuals not erected. Tooth count of upper jaw 22–28 (23), lower jaw 32–42, total count 54–70.

Figure 3. 

Boxplot showing difference in the cusplet pairs of sexes and ontogenetic stages between Etmopterus spp. A Etmopterus abernethyi B E. lucifer C E. molleri D E. schmidti. The ontogenetic stages of female are not shown as they were not determined in most cases.

First dorsal fin (D1) long and rather small, with round apex, origin just below to posterior to a vertical line through pectoral-fin (P1) free rear tip. Second dorsal fin (D2) larger than D1, apex angular, posterior margin especially concave, free rear tip moderately elongated; D2 spine long and curved. P1 moderate in size, with angular free rear tips, base narrow, posterior margin slightly concave. Pelvic fin (P2) narrowly triangular. Clasper of mature males rather long. Caudal fin elongate, caudal fork not especially developed; terminal lobe broad.

Dermal denticles hook-like, rather high, recurved (Fig. 4A), widely-spaced, not overlapping, giving a rough texture of the skin, in defined rows; denticles present on underside of snout, except for a broad area around mouth; underside of gill slits fully covered with denticles (small bare patch rarely present between underside of gill slits); P1 inner margin with a broad naked area, D1, D2 and P2 inner margins with narrow naked areas; denticles present on fin bases; denticles scarcely distributed on fins in juveniles, increasing the coverage to most of the areas of ceratotrichia with increasing size, especially prominent on D2 (Fig. 5A).

Figure 4. 

Dermal denticles below second dorsal fin of Etmopterus spp. A Etmopterus abernethyi, holotype, NMMZ P.01951, immature male 330 mm TL B Etmopterus lucifer, EBFS-NG 00105, mature male 371 mm TL C E. molleri, NMMZ P.045558, mature male 359 mm TL D E. schmidti, EBFS-NG 00095, mature female 307 mm TL.

Figure 5. 

Details of the dermal coverage on the second dorsal fin of Etmopterus spp. A Etmopterus abernethyi, holotype, NMMZ P.01951, immature male 330 mm TL B E. lucifer, EBFS-NG 00105, mature male 371 mm TL C E. molleri, AMS I.44904-001, mature female 381 mm TL D E. schmidti, EBFS-NG 00095, mature female 307 mm TL.

Body lateral side with short, dash-like markings; head dorsal surface with scattered dot-like markings; dorsal contour of the body with a single line of dot-like markings, extending mid-dorsally from about the level of anterior fontanelle to origin of D2; ventral pectoral marking elongated and arched (Fig. 6A, C), its tip falling short of P1 insertion. Flank markings well defined, with elongated anterior and posterior branches; anterior flank marking slender, slightly curved, extending above P2 origin; posterior flank marking straight, slightly thicker, usually shorter than anterior flank marking (rarely longer than anterior flank marking); anterior flank marking length 92.1–182.5 (132.7)% posterior flank marking; posterior flank marking usually not extending beyond D2 free rear tip; flank marking base rather narrow, origin well posterior to D2 origin. Infracaudal marking prominent, extending from flank marking base to about the same level of posterior flank marking tip, connecting to the caudal-base marking by a pair of lines formed by bioluminescent melanophores (Fig. 7A, C; see also Duchatelet et al. 2021); caudal-base marking broad, with a moderately thick, slender extension, bifurcate before lower caudal-fin origin, length 17.4–31.3 (30.5)% caudal-fin length. Posterior caudal-fin marking very long, its length 30.2–46.5 (38.9)% caudal-fin length.

Figure 6. 

Ventral pectoral markings (A, B) and their schematic illustrations (C, D) of Etmopterus abernethyi (A, C) and E. lucifer (B, D). A holotype, NMMZ P.01951, immature male 330 mm TL B lectotype (designated herein), CAS-SU 6863, mature male 264 mm TL.

Figure 7. 

Infracaudal markings (A, B) and their schematic illustrations (C, D) of Etmopterus abernethyi (A, C) and E. lucifer (B, D). A holotype, NMMZ P.01951, immature male 330 mm TL B lectotype, CAS-SU 6863, mature male 264 mm TL.

When fresh, body generally shiny grey to dark grey, black ventrally; transition between lateral and ventral sides strongly demarcated. Dorsal midline with pale stripe; P1 and P2 generally translucent, with darker bases; dorsal fins mostly pale grey in the proximal two-thirds of ceratotrichia. Caudal-fin dorsal and postventral margins black, without a dark blotch on mid-caudal fin. No black blotch between infracaudal marking and caudal-base marking. Caudal fin with distinct black tip at terminal margin.

After preservation, body coloration slightly darker, yet most of markings remaining distinct. Transition between lateral and ventral sides becoming less demarcated.

One specimen (NMNZ P.031152, 1 of 3 specimens, pregnant female 439 mm TL) with an extremely long posterior flank marking, anterior flank marking 74.6% posterior flank marking, with tip almost extending to lower caudal-fin origin (Fig. 8), but otherwise identical to other E. abernethyi.

Figure 8. 

Unusual variant of Etmopterus abernethyi, NMNZ P.031152 (1 of 3 specimens), pregnant female 439 mm TL, northeastern Chatham Rise, New Zealand. A lateral view B detail of the flank marking. Note tip of posterior branch. Scale bars=20 mm.

Up to 527 mm TL and 403 mm TL for females and males, respectively. Smallest mature male 325 mm TL; smallest of five mature females 432 mm TL. Smallest specimen studied here without umbilical scar measuring 206 mm TL.

Southwestern Pacific and also southeastern Indian Ocean, known from southeastern, southern, and southwestern Australia, the Tasman Sea, and around New Zealand, at depths of 180–872 m. Common at catches in research cruises in Australian waters (K Graham pers. comm.), uncommon in commercial trawlers around New Zealand (Roberts et al. 2015).

Etmopterus abernethyi was described from off New Zealand by Garrick (1957). Soon afterwards, Garrick (1960) recognized that the diagnostic characters of E. abernethyi in Garrick (1957) were actually due to ontogenetic and intraspecific variations and that this species was not separable from E. lucifer. Despite direct comparisons with E. lucifer specimens from Japan and E. molleri from southwestern Australian waters, Garrick (1960) was not able to find morphological differences between the two species, although he mentioned that most of the New Zealand specimens possess a distinct shape of their luminescent areas on the ventral surface of the caudal peduncle. Thus, he synonymized E. abernethyi and E. molleri with E. lucifer. Subsequently, the former was generally considered a junior synonym of E. lucifer (e.g., Compagno 1984 [as E. abernathyi]; Yamakawa et al. 1986; Last and Stevens 1994; Weigmann 2016). In contrast, Yamakawa et al. (1986) resurrected E. molleri, and further identified the sole paratype of E. abernethyi as belonging to E. molleri.

Re-examination of the type series and numerous non-types of E. abernethyi and E. lucifer shows distinct character differences separating the two species. The types of E. abernethyi as well as other specimens from the southwestern Pacific previously identified as E. lucifer, are all characterized by an elongated and arched ventral pectoral marking, which is strongly contrasted with the stout and knife-shaped ventral pectoral marking in specimens of E. lucifer from the northwestern Pacific (Fig. 6A, C). Another consistent character difference between the two species is the shape of the infracaudal marking, which is connected to the caudal-base marking by a pair of lines in the types of E. abernethyi and the other southwestern Pacific specimens, but is not connected in the northwestern Pacific E. lucifer (Fig. 6B, D). These luminescent lines are especially prominent in life (see Duchatelet et al. 2021: fig. 2 [as E. lucifer]).

Although very similar to each other morphologically, the consistency of the small differences in markings warrants specific separation. The genetic evidence further supported the separation of the two lineages. As a result, E. abernethyi is resurrected here to represent records hitherto assigned to E. lucifer in the southwestern Pacific.

Yamakawa et al. (1986) identified the paratype of E. abernethyi as a specimen of E. molleri. our re-examination of this paratype, however, reconfirms its conspecificity with E. abernethyi evidenced by having the origin of flank marking base behind a vertical line through D2 origin, and the infracaudal marking connected to the caudal-base marking by a pair of lines.

Etmopterus abernethyi belongs to the E. lucifer group, as defined by Straube et al. (2010), in having elongated anterior and posterior branches of the flank marking. It is most similar to E. lucifer, with both having a combination of hook-like denticles, the origin of flank marking base behind a vertical line through D2 origin, and a rather long posterior caudal-fin marking. They are also similar in morphometric characters and overlap in vertebral counts. Etmopterus abernethyi can be distinguished from E. lucifer by an elongated and arched ventral pectoral marking (vs. ventral pectoral marking stout and knife-like in E. lucifer; Fig. 6), and the infracaudal marking connected to the caudal-base marking by a pair of lines (vs. not connected; Fig. 7). In addition, the ratio of the lengths of the anterior flank-marking branches relative to that of the posterior branches is significantly lower in E. abernethyi than E. lucifer (Mann-Whitney U test, p<0.01). This means that the anterior branch is usually slightly longer than the posterior branch in E. abernethyi, while the anterior branch is usually significantly longer than the posterior branch in E. lucifer (Fig. 9). Further, E. abernethyi has a broad distribution from the southeast to southwest Australia, the Tasman Sea, and around New Zealand, while E. lucifer is found from subboreal Northwest Pacific off Japan to the tropical northern South China Sea.

Figure 9. 

Boxplot showing difference in the relative length of anterior flank marking to posterior flank marking comparing Etmopterus spp. Different letters indicate statistical differences (p<0.05) between species. Abbreviations: AFM, anterior flank marking; PFM, posterior flank marking.

In the southwestern Pacific, E. abernethyi may be confused with the sympatric E. molleri. The former is readily distinguished from the latter by having the origin of the flank marking base behind a vertical line through D2 origin (vs. the origin of the flank marking base well before a vertical line through D2 origin in E. molleri), the infracaudal marking connected to the caudal-base marking by a pair of lines (vs. not connected), fewer diplospondylous trunk vertebrae (11–18 vs. 20–21) and dorsal fins heavily covered with denticles in adults (vs. largely naked). The length of anterior branch of flank marking relative to the posterior branch is also significantly higher in E. abernethyi than in E. molleri (Mann-Whitney U test, p<0.01, Fig. 9).

51 specimens. Lectotype (designated herein): CAS-SU 6863, mature male 264 mm TL, off Misaki, Japan, 35°14'N, 139°37'E, depth and date unknown. Paralectotype: CAS-SU 7832 (1 of 4 specimens), mature male 284 mm TL, collected with the lectotype. Holotype of Etmopterus burgessi: CAS 223476, mature male 355 mm TL, Daxi, Taiwan, 24°53'N, 122°01'E, 300 m, 11 May 1988. Paratypes of Etmopterus burgessi: CAS 223477, female 405 mm TL, CAS 223478, female 241 mm TL, CAS 223479, female 235 mm TL, Daxi, Taiwan, 24°53'N, 122°01'E, 300 m, 21 May 2005. Non-types: ASIZP0060498 (2 specimens), females 345–357 mm TL, 24°56'N, 121°54'E, off Daxi, northeastern Taiwan, 10 February 1997; CAS-SU 26782, female 305 mm TL, Japan, depth and date unknown; EBFS-NG 00020, juvenile female 150 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 15 April 2022; EBFS-NG 00047, mature male 317 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 19 November 2021; EBFS-NG 00048, mature male 342 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 25 November 2022; EBFS-NG 00049, female 298 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 1 March 2022; EBFS-NG 00074, mature male 313 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 9 July 2021; EBFS-NG 00105, mature male 371 mm TL, off Donggang, southwestern Taiwan, ca. 22° N, 120° E, ca. 400 m, 25 March 2022; EBFS-NG 00124, mature male 324 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 18 May 2022; EBFS-NG 00142, mature male 328 mm TL, EBFS-NG 00143, juvenile female 204 mm TL, EBFS-NG 00144, female 314 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 8 July 2022; EBFS-NG 00145, juvenile female 189 mm TL; EBFS-NG 00146, juvenile female 247 mm TL, EBFS-NG 00147, juvenile female 284 mm TL, EBFS-NG 00148, juvenile female 274 mm TL, EBFS-NG 00149, juvenile male 287 mm TL, EBFS-NG 00150, juvenile male 296 mm TL, EBFS-NG 00151, juvenile male 261 mm TL, EBFS-NG 00152, juvenile male 284 mm TL, EBFS-NG 00153, juvenile male 315 mm TL, EBFS-NG 00154, juvenile male 300 mm TL, EBFS-NG 00155, mature male 333 mm TL, EBFS-NG 00156, mature male 334 mm TL, EBFS-NG 00157, mature male 365 mm TL, off Daxi, northeastern Taiwan, ca. 24°53'N, 122°00'E, ca. 400 m, 30 May 2022; EBFS-NG 00267, off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 24 August 2022; EBFS-NG 00270, female 259 mm TL, EBFS-NG 00271, mature male 313 mm TL, EBFS-NG 00272, female 213 mm TL, EBFS-NG 00273, EBFS-NG 00274, EBFS-NG 00275, off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 7 October 2022; EBFS-NG 00286, juvenile female 165 mm TL, EBFS-NG 00287, juvenile male 173 mm TL, EBFS-NG 00288, juvenile male 175 mm TL, EBFS-NG 00289, juvenile male 161 mm TL, off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 9 November 2022; EBFS-NG 00323, juvenile male 290 mm TL, EBFS-NG 00324, juvenile male 321 mm TL, off Donggang, southwestern Taiwan, ca. 22°N, 120°E, ca. 400 m, 10 January 2023; EBFS-NG 00354, juvenile male 287 mm TL, South China Sea, ca. 19°N, 114°E, ca. 500 m, 12 March 2023; HUMZ 214505, off Tohoku, Japan, 40°17'N, 142°16'E, 441–459 m, 10 October 2011; HUMZ 232154, neonate female 131 mm TL; HUMZ 232155, mature male 268 mm TL, off Miyagi, Japan, 38°36'N, 142°02'E, 378 m, 22 October 2021; HUMZ 232462, female 358 mm TL, off Tomakomai, Japan, 42°13'N, 141°41'E, 656–684 m, 24 November 2021; NTUM16305, mature male 283 mm TL, CP4175, northeastern Taiwan, ca. 25°25'N, 122°08'E, ca. 434–535 m, 28 June 2018; USNM 51282, mature male 285 mm TL, off Sagami Bay, Japan, depth unknown, 1900.

A moderately small Etmopterus of the E. lucifer group by showing elongated anterior and posterior branches of lateral flank marking, and differing from other members of the E. lucifer group by the following combination of characters: hook-like dermal denticles not overlapping each other, in well-defined rows; origin of second dorsal fin anterior to flank-marking base origin; infracaudal marking not connected with caudal-fin base marking through luminous lines; posterior caudal-fin marking long, its length 23.1–39.8% caudal-fin length; and ventral pectoral marking knife-shaped, straight.

Morphometric information is provided in File S2 (Table S2). Proportional measurements and tooth counts are provided as ranges for the paralectotype and the non-types, followed by the lectotype (designated herein) in parentheses (if available). A precise tooth count of the lower jaw teeth is not possible in the lectotype as several teeth are missing.

Trunk sub-cylindrical, body width narrower than to slightly wider than height; abdomen longer than lower caudal peduncle; head subconical, slightly depressed. Snout moderately short (Fig. 10), snout narrowly rounded in lateral and dorsal view. Eye oval. Spiracle bean-shaped. Gill openings moderate, slightly curved. Mouth broad, nearly straight.

Figure 10. 

Etmopterus lucifer. A Lectotype (designated herein), CAS-SU 6863, mature male 264 mm TL, off Misaki, Japan B fresh specimen, EBFS-NG 00047, mature male 317 mm TL, off Daxi, northeastern Taiwan C HUMZ 232154, neonate female 131 mm TL, off Miyagi, Japan. Scale bars=20 mm.

Teeth dissimilar in upper and lower jaw, exhibiting ontogenetic change and sexual dimorphism; upper teeth multicuspid in three functional series; lower teeth unicuspid, in three series, one functional; lower teeth blade-like, with strongly oblique cusp. No distinctive symphyseal and intermediate teeth. Upper teeth cusp thick; immature males and females with 1–2, rarely 3 cusplets on each side of the upper teeth, while mature males having 3, rarely 2 or 4 cusplets (Fig. 3B); longest cusplet length about two-third of the cusp in mature individuals; cusp and cusplets of upper teeth narrowly triangular, lower teeth of mature individuals not erected. Tooth count of upper jaw 22–28 (25), lower jaw 25–35, total count 47–62.

D1 rather small, with a round apex, origin usually posterior to a vertical line through P1 free rear tip. D2 larger than D1, apex angular, posterior margin remarkably concave, free rear tip moderately elongated; D2 spine long and curved. P1 with moderate size, and angular free rear tips, base narrow, posterior margin slightly concave. P2 narrowly triangular. Clasper of mature males moderately long. Caudal fin elongate, caudal folk not especially developed; terminal lobe broad.

Dermal denticles hook-like, rather high, reclined backwards, widely-spaced, not overlapping, giving a rough texture of the skin, in defined rows (Fig. 4B); denticles present on underside of snout, except for a broad area around mouth; underside of gill slits fully covered with denticles (small bare patch maybe present between underside of gill slits in juveniles); P1 inner margin with a broad naked area, D1, D2 and P2 inner margins with narrow naked areas; denticles present on fin bases; denticles scarcely present on fins in neonates, increasing the coverage to most of the areas of ceratotrichia, particularly on D2 (Fig. 5B).

Body lateral side with very short, dash-like markings which are usually difficult to observe after preservation; head dorsal surface scattered dot-like markings; dorsal contour of the body with a single line of dot-like markings, extending mid-dorsally from about the level of anterior fontanelle to the D2 origin; ventral pectoral marking knife-like, straight, the tip not reaching P1 insertion (Fig. 6B, D). Flank markings well defined, with elongated anterior and posterior branch; anterior flank marking slender, very slightly curved, extending above P2 origin; posterior flank marking straight, usually thicker, shorter than anterior flank marking; anterior flank marking length 101.7–180.4 (167.4)% posterior flank marking; posterior flank marking not extending beyond D2 free rear tip; flank marking base rather narrow, origin well posterior to D2 origin. Infracaudal marking prominent, extending from flank marking base to about the same level of posterior flank marking tip, not connecting to the caudal-base marking by a pair of lines (Fig. 7B, D); caudal-base marking broad, with a moderately thick, slender extension, bifurcate before the lower caudal-fin origin, 15.7–38.5 (29.6)% caudal-fin length. Posterior caudal-fin marking long, its length 23.1–39.8 (35.2)% caudal-fin length.

When fresh, body usually dark grey to brown, rarely pale grey, turning almost black after frozen or when the specimen is no longer fresh; darker ventrally; transition between lateral and ventral sides strongly demarcated in life (moderately demarcated when not fresh). Dorsal midline with a pale stripe; P1 and P2 generally translucent, with darker bases; dorsal fins mostly pale grey in the proximal two-thirds of ceratotrichia. Caudal-fin dorsal and postventral margins black, with a dark blotch on mid-caudal fin (faded when not fresh). A black blotch present between infracaudal marking and caudal-base marking. Caudal fin with a distinct black tip on the terminal margin.

After preservation, body coloration usually much darker, black blotches between infracaudal marking and caudal-base marking, and on mid-caudal fin, become less distinct. Transition between lateral and ventral sides becomes less demarcated.

Largest examined mature male is 371 mm TL. One female reported to attain about 450 mm TL (Dolganov 2006). Schaaf-Da Silva and Ebert (2006) considered the largest female paratype of E. burgessi (CAS 223477, 405 mm TL) to be mature, however, the gonads of this specimen were not available for observation as it was not dissected, thus, the maturity cannot be determined by us. No mature female was examined in the present study. The lectotype (designated herein) represents the smallest mature male examined (264 mm TL). The size at birth is about 131 mm TL.

Northwestern Pacific, from sub-boreal northern Japan to the tropical South China Sea, at depths of 300–500 m. Common in Japanese waters and around Taiwan, but seems rare in the northern South China Sea.

Etmopterus lucifer was originally described by Jordan and Snyder (1902) from off Misaki (Sagami Bay, Japan) based on a number of specimens. We examined all available syntypes in the present study and we found that they belong to two different species. To solve this confusion and to unambiguously fix the name E. lucifer, we select one of the syntypes, CAS-SU 6863, as the lectotype of this species (Fig. 10A). The remaining syntypes, CAS-SU 7832 (four specimens), USNM 50728, are paralectotypes, which we have re-identified as Etmopterus schmidti Dolganov, 1986, except the sole male specimen of CAS-SU 7832, which we have identified as E. lucifer.

Previously, the single specimen in CAS-SU 6863, which we have designated as lectotype here, was incorrectly considered as holotype of E. lucifer (e.g., Böhlke 1953; Yamakawa et al. 1986; Schaaf-Da Silva and Ebert 2006; Ebert et al. 2016; White et al. 2017) mainly based on Böhlke’s (1953) assessment, which does not conform to ICZN Art. 74.5.

Schaaf-Da Silva and Ebert (2006) described E. burgessi from Taiwan, and stated that this species differed from E. lucifer by having more lateral cusplets (3 on each side vs. 2 on each side in E. lucifer) and shorter caudal peduncle (11.1–12.7 vs. 12.8% TL). Schaaf-Da Silva and Ebert (2006) also stated in their key that E. burgessi possessed {Gill openings very long, snout broad. Ventral surface of snout covered with thick dermal denticles. Color in life dark gray above, black below}, which differed from the characters of E. lucifer {Gill openings moderately long, snout narrow. Ventral surface of snout lacking dermal denticles. Color in life brown above, black below}. Later, Ebert and van Hees (2018) assigned E. burgessi and E. lucifer into two subgroups of the E. lucifer group, the E. burgessi subgroup and the E. lucifer subgroup, by the relative length of the anterior and posterior flank-marking branches: members of the E. burgessi subgroup have similar length of anterior and posterior flank-marking branches, while members of the E. lucifer subgroup shows notably longer anterior flank-marking branch.

The above characters are not diagnostic when comparing numerous specimens from near the type localities: the lateral cusplet number of upper teeth is depending on the sex, with males having more cusplets (Straube et al. 2008; Straube and Pollerspöck 2020; Ng et al. 2024a; present study); all of the specimens have their underside of the snout fully covered with denticles, except the lectotype of E. lucifer (designated above), which has a rather smooth underside of snout. Visual inspection using a microscope reveals numerous holes corresponding in size and density to former denticle positions suggesting that abrasion of dermal denticles on the underside of the snout is the most likely explanation for their lack in the lectotype; morphometric characters substantially overlap between E. burgessi and E. lucifer when examining further specimens; coloration in life varies greatly depending on the environment and the condition of the specimen, and is very rarely used for distinguishing lanternshark species. Particularly noteworthy is the relative length of the anterior and posterior flank-marking branches. After analyzing DNA sequence information of numerous specimens collected from around Taiwan, and some in Japan and the South China Sea, we found very little genetic differences between specimens with longer anterior flank-marking branches and specimens with both branches similar in length (K2P distance=0–0.007), which strongly suggests intraspecific morphological variation and therefore conspecificity of these specimens, which otherwise would have been identified as E. burgessi and E. lucifer. Further, the length of the anterior flank marking of the holotype of E. burgessi is 155.2% of that of the posterior flank marking (Fig. 11), which is in conflict with the establishment of sub-groups as defined in Ebert and van Hees (2018).

Figure 11. 

Etmopterus burgessi, holotype, CAS 223476, mature male 355 mm TL, Daxi, Taiwan. A lateral view B detail of the flank marking. Scale bars=20 mm.

Straube et al. (2013) stated that E. burgessi formed a distinct cluster in their molecular analysis which is the sister group to a group comprising E. lucifer. However, the analyzed E. lucifer samples were collected off New Zealand, which is not only far away from the type locality (=Japan), but these samples represent E. abernethyi based on results of our present study. Straube et al. (2013) simply lacked samples of true E. lucifer in their study. Here, we included E. lucifer from Japan in the molecular analyses for the first time, which showed that E. lucifer and E. burgessi together form a group with small intra-group genetic distances. The genetic divergence between E. burgessi from Taiwan and E. lucifer from Japan is only 0.1–0.7% (x̄=0.3%) and well within the range of intraspecific variation. As we were not able to detect significant morphological and molecular differences between E. burgessi and E. lucifer, we herein synonymize the former species name with the latter.

Compagno et al. (2005) reported the occurrence of E. lucifer around the Philippines based on specimens mentioned in Smith and Radcliffe (1912). These specimens, currently housed at USNM and examined in the course of the present study, are all reidentified as E. marshae Ebert & van Hees, 2018. Ebert and van Hees (2018) further confirmed the presence of E. lucifer in the Philippines based on two specimens (CAS 233994). However, the specimens could not be located during SLN’s visit to CAS, and might have been lost and the occurrence of E. lucifer from around Philippines needs to be confirmed. The southernmost distribution of E. lucifer according to the present study (EBFS-NG 00354) is the northern South China Sea.

Despite great sampling effort, no mature females were collected and these are also poorly represented in museum collections, with the largest being the 405 mm TL paratype of E. burgessi (CAS 223477). It is possible that mature females escape sampling efforts because they inhabit much greater depths, than males and immature females, which are both sampled more frequently. Sexual segregation in habitats has also been reported in two congeners (Porcu et al. 2014; Karampetsis et al. 2022; Ng et al. 2024a).

Preliminary data suggest males to mature at larger sizes around Taiwan (smallest mature male=313 mm TL) than Japan (smallest mature male: 264 mm). This would be unusual as usually in sharks the size at maturity is smaller at lower latitudes (e.g., Baje et al. 2018). While little is known on the biology of lanternsharks in general, this phenomenon needs further investigation.

Etmopterus lucifer is most similar to E. abernethyi (see comparisons of the latter species). It differs from E. molleri and E. schmidti by flank marking base originating behind a vertical line through the D2 origin (vs. origin of flank marking base well before vertical line through D2 origin in E. molleri and E. schmidti), dorsal fins densely covered with denticles in adults (vs. almost naked in E. molleri and E. schmidti; Fig. 5), and knife-shaped, straight ventral pectoral marking (vs. elongated and arched marking in E. molleri and E. schmidti; Fig. 6).

36 specimens. Holotype: AMS IA.5816, female 350 mm+ TL, off New South Wales, Australia, 33°50'S, 151°50'E, 238 m, June 1933. Paratype: AMS IA.5817, mature female 333 mm TL, collected with the holotype. Non-types: AMS I.15975-001, female 275 mm TL; AMS I. 15975-002, juvenile male 266 mm TL; AMS I.15975-003, female 291 mm TL; AMS I.15975-004, female 303 mm TL; AMS I.15975-005, 322 mm TL; AMS I.15975-006, female 366 mm TL; AMS I.15975-008, female 389 mm TL, off Macquarie Island, southeastern Australia, 33°11'S, 152°23'E, 29 April 1971; AMS I.19385-004, mature male 335 mm TL, east of Broken Bay, southeastern Australia, 33°28'S, 152°05'E, 26 May 1976, coll. K. Graham; AMS I.19860-008, pregnant female 415 mm TL, off Broken Bay, southeastern Australia, 33°35'S, 152°01'E, 20 December 1976, coll. K. Graham; AMS I.22642-004, female 390 mm TL, east of Tuncurry, southeastern Australia, 32°07'S, 153°05'E, 27 July 1981, coll. K. Graham; AMS I.42758-003, female 433 mm TL, Western Norfolk Ridge, Tasman Sea, 32°35'S, 167°38'E, 30 May 2003; AMS I.44904-001, mature female 381 mm TL, Port Stephens, southeastern Australia, 32°30'S, 152°55'E, 9 September 2009, coll. K. Graham; AMS I.44907-010, female 324 mm TL, off Coffs Habour, eastern Australia, 30°30'S, 153°25'E, 6 September 2009, coll. K. Graham; AMS I.44909-007, female 359 mm TL, Browns Mountain, southeastern Australia, 34°00'S, 151°40'E, 16 September 2009, coll. K. Graham; AMS I.44992-001 (4 specimens), females 346–380 mm TL, 31 Canyon, eastern Australia, 31°08'S, 153°20'E, 7 September 2009, coll. K. Graham; CSIRO H 7030-02 (3 specimens), juvenile males 219–267 mm TL; CSIRO H 7030-03, mature male 351 mm TL; CSIRO H 7030-04, female 376 mm TL, east of Port Stephens, southeastern Australia, 32°30'S, 152°55'E, 500 m, 9 September 2009; CSIRO H 7054-04, mature male 349 mm TL; CSIRO H 7054-05, female 356 mm TL, east of Sydney, southeastern Australia, 34°02'S, 151°39'E, 450 m, 16 September 2009; CSIRO H 7059-02, female 389 mm TL, east of Sydney, southeastern Australia, 33°40'S, 151°55'E, 530 m, 15 September 2009; CSIRO H 7216-01, adolescent male 323 mm TL, Britannia Seamount, eastern Australia, 28°39'S, 155°34'E, 366 m, 3 February 2011; NMNZ P.029400 (2 specimens), female 296–371 mm TL, southern New Caledonia, 24°55'S, 168°36'E, 502–610 m, 14 October 1992; NMNZ P.045558, mature male 359 mm TL, Bay of Plenty, New Zealand, 37°42'S, 176°54'E, 367–450 m, January 2009; NMNZ P.045561, mature female 409 mm TL, locality and date unknown; NMNZ P.047803, mature male 366 mm TL, off Mayor Island, New Zealand, 37°29'S, 176°34'E, 220 m, 2010; NMNZ P.049671, pregnant female 412 mm TL, southeastern Mayor Island, New Zealand, 37°41'S, 176°49'E, 360–373 m, 30 October 2010; NMNZ P.056140, mature female 406 mm TL, off Tauranga, New Zealand, 37°40'S, 176°41'E, 21 July 2013.

A moderately small Etmopterus belonging to the E. lucifer group by having elongated anterior and posterior branches of lateral flank marking, and differing 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; a long posterior caudal-fin marking, length 18.8–38.1% caudal-fin length; caudal fin black; caudal-base marking bifurcated before caudal-fin origin; and ventral pectoral marking curved.

Morphometric information is provided in File S2 (Table S3). Proportional measurements and tooth counts are expressed as ranges for the paratype and the non-types, followed by the holotype in parentheses. A precise tooth count is not possible in the holotype as several teeth are missing.

Trunk sub-cylindrical, body width narrower than to slightly wider than height; abdomen usually longer than lower caudal peduncle, usually shorter in mature males; head subconical, moderately depressed. Snout fairly long (Fig. 12), preorbital length 25.5–43.3 (27.0)% head length; snout narrowly rounded in lateral and dorsal view. Eye oval. Spiracle bean-shaped. Gill openings short, slightly curved. Mouth broad, slightly arched. Preoral length relatively long, length 44.1–52.7 (44.1)% head length.

Figure 12. 

Etmopterus molleri. A holotype, AMS IA.5816, female 350 mm+ TL, off New South Wales, Australia B Paratype, AMS IA.5817, mature female 333 mm TL, off New South Wales, Australia C fresh specimen, CSIRO H 7059-02, female 389 mm TL, east of Sydney, southeastern Australia (photo provided by CSIRO Australian National Fish Collection, used with permission). Scale bars=20 mm. All images are horizontally flipped.

Teeth dissimilar in upper and lower jaw, having ontogenetic change and sexual dimorphism; multicuspid upper teeth in three functional series; unicuspid lower teeth in three series, with one functional; lower teeth blade-like, strongly oblique. No symphyseal and intermediate teeth. Upper teeth cusp thick; immature males and females with 1–2 cusplets on each side of the upper teeth (rarely 3 in mature females), while mature males having 3–4 cusplets (Fig. 3C); longest cusplet length about two-third of the cusp in mature individuals; cusp and cusplets of upper teeth narrowly triangular, lower teeth of mature individuals not erected. Tooth count of upper jaw 23–26, lower jaw 38–40, total count 61–66.

D1 small, with a round apex, origin anterior to slightly posterior a vertical line through P1 free rear tip. D2 larger than D1, apex angular, posterior margin especially concave, free rear tip moderately elongated; D2 spine long and curved. P1 moderate in size, with angular free rear tips, base narrow, posterior margin slightly concave. P2 narrowly triangular. Clasper of mature males rather long. Caudal fin elongate, caudal folk not especially developed; terminal lobe broad.

Dermal denticles hook-like, fairly low, slightly reclined backwards, widely-spaced, not overlapped, giving a rough texture of the skin, in defined rows (Fig. 4C); denticles present on underside of snout, except for a broad area around mouth (small bare patch maybe present on underside of snout in juveniles); underside of gill slits fully covered with denticles (small bare patch maybe present between underside of gill slits in juveniles); Inner margin of fins with a broad naked area; denticles present on fin bases, but almost absent on fins (Fig. 5C).

Lateral body side with prominent short, dash-like markings which are usually still distinct after preservation; head dorsal surface scattered with dot-like markings; dorsal contour of the body with a single line of dot-like markings, extending mid-dorsally from about the level of anterior fontanelle to the D2 origin; ventral pectoral marking elongated and arched, the tip not reaching P1 insertion. Flank markings well defined, with elongated anterior and posterior branch; anterior flank marking slender, a little bit curved, extending above P2 origin; posterior flank marking straight, not much thicker, longer than anterior flank marking; anterior flank marking length 53.8–91.8 (69.2)% posterior flank marking, usually with pointed tip; posterior flank marking usually not extending beyond D2 free rear tip; flank marking base rather narrow, origin well anterior to D2 origin. Infracaudal marking prominent, extending from flank marking base to about the same level of posterior flank marking tip, not connecting to the caudal-base marking by a pair of lines; caudal-base marking broad, with a moderately thick, slender extension, bifurcate before the lower caudal-fin origin (Fig. 13A, C), length 19.2–36.5% caudal-fin length. Posterior caudal-fin marking long, its length 18.8–38.1% caudal-fin length.

Figure 13. 

Lateral (A, B) and ventral view (C, D) of the caudal-base marking of Etmopterus molleri (A, C) and E. schmidti (B, D). A, C holotype, AMS IA.5816, female 350 mm+ TL B, D EBFS-NG 00095, mature female 307 mm TL. Blue arrows in (B) and (D) indicates the small black portion covering the lower caudal-fin origin. Grey dotted lines depict the lower caudal-fin origin.

When fresh, body shiny to brownish grey; much darker ventrally; transition between lateral and ventral sides strongly demarcated. Dorsal midline with a pale stripe; Fins, except caudal fin, generally translucent, with darker anterior margins and bases. Caudal-fin dorsal and postventral margins black (Fig. 14A), with a very narrow translucent upper postventral margin; darker blotch present on mid-caudal fin. A black blotch present between infracaudal marking and caudal-base marking. Caudal fin with a distinct black tip on the terminal margin.

Figure 14. 

Details of the coloration of the caudal fin. A Etmopterus molleri, NMMZ P.045558, mature male 359 mm TL B E. schmidti, EBFS-NG 00095, mature female 307 mm TL. Black arrow in (B) indicates the translucent portion of the caudal fin.

After preservation, body coloration becomes darker; black blotch on mid-caudal fin become difficult to be observed.

Up to 433 mm TL and 366 mm TL for females and males, respectively. Smallest mature female and male examined are 333 and 335 mm TL, respectively.

Southwestern Pacific, off southeastern Australia to northern New Zealand, and New Caledonia, at 366–530 m depth.

Bigelow and Schroeder (1957) concluded that E. molleri does not differ from E. brachyurus based on the description and illustration of the former. In contrast, Garrick (1960) considered E. molleri a junior synonym of E. lucifer based on the similar relative lengths of upper caudal margin to the pelvic–caudal space (80% vs. 83% in the E. lucifer specimen Garrick examined). He also considered E. brachyurus to be distinct from E. molleri as the former has a shorter relative length of the upper caudal margin to the pelvic–caudal space (70% vs. 80% in E. molleri). However, the relative length of the upper caudal margin to the pelvic–caudal space, as well as the two measurements relative to total length, show prominent intraspecific variation and perhaps sexual dimorphism, which results in substantial overlap. As a result, the characters proposed by Garrick (1960) arguing for synonymy of the two species cannot be supported in the present study. In addition, at least one of the E. lucifer specimens examined by Garrick (1960) represents E. molleri, based on the characters defined here for E. molleri, i.e., the position of the characteristic anterior origin of the flank-marking base relative to that of the second dorsal-fin origin (plate 26: Figure D).

Etmopterus molleri can be assigned to the E. lucifer group and is most similar to E. schmidti, which explains why the two species have been confused for nearly 40 years. Morphometrics of the two species almost entirely overlap, except for snout length, in which E. molleri has a significantly longer preorbital length relative to the head length (25.5–43.3% vs. 19.7–29.6% in E. schmidti; Mann-Whitney U test, p<0.05); and a significantly longer preoral length relative to the head length (44.1–52.7% vs. 32.7–45.4% in E. schmidti; Mann-Whitney U test, p<0.05). Further, E. molleri possesses slightly more total vertebrae (89–93 vs. 78–88 in E. schmidti). In addition, E. molleri can be distinguished from E. schmidti by having the caudal-base marking bifurcate before the caudal-fin origin (bifurcate after caudal-fin origin, especially prominent when viewed laterally in E. schmidti; Fig. 13), and having a black caudal-fin upper lobe (vs. translucent upper lobe in E. schmidti; Fig. 14). Geographically, E. molleri is restricted to the southwestern Pacific, being found from Eastern and Southeastern Australia to New Caledonia, and northern New Zealand.

Etmopterus molleri is also quite similar to E. brachyurus, yet can be separated by the underside of snout and gill slits being mostly fully covered with denticles (vs. underside of snout with a reversed ‘W’ shaped naked area, underside of gill slits with a ‘V’ shaped naked area connecting the first gill slits in E. brachyurus); the second dorsal fin lacking denticles in all developmental stages (vs. covered with denticles in subadults and adults); caudal-fin base marking with a narrowly rounded tip (vs. strongly pointed tip).

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.

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.

Morphometric information is provided in File S2 (Table S3). 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), 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.

Figure 15. 

Etmopterus schmidti. A holotype, ZIN 22362, Sagami Sea, Japan (photo provided by ZIN, used with permission) B paralectotype (designated herein) of Etmopterus lucifer, USNM 50728, mature male 273 mm TL, off Sagami Bay, Japan C fresh specimen, EBFS-NG 00134, mature female 333 mm TL, off Daxi, northeastern Taiwan. Scale bar=20 mm.

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. 3D); 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).

D1 small, with a broadly round apex, origin usually slightly posterior a vertical line through P1 free rear tip. D2 larger than D1, apex broadly angular, posterior margin especially concave, free rear tip moderately elongated; D2 spine long and variously curved. P1 with moderate size, with angular free rear tips, base narrow, posterior margin slightly concave. P2 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. 4D); 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. 5D).

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 D2 origin; ventral pectoral marking elongated and arched, tip not reaching P1 insertion. Flank markings well defined, with elongated anterior and posterior branch; anterior flank marking slender, slightly curved, extending above P2 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 D2 free rear tip; flank marking base rather narrow, origin well anterior to D2 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. 13B, D). Posterior caudal-fin marking moderately long, its length 20.4–34.4% caudal-fin length.

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. 14B); 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.

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.

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

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. 15A, 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.

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.

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).