Squalus japonicus Ishikawa, 1908

Viana, Sarah T. F. L. & Carvalho, Marcelo R. de, 2020, Squalus shiraii sp. nov. (Squaliformes, Squalidae), a new species of dogfish shark from Japan with regional nominal species revisited, Zoosystematics and Evolution 96 (2), pp. 275-311 : 275

Squalus japonicus Ishikawa, 1908 Figs 3E, F , 4 , 7G, H , 8C ; Tables 3, 6 Japanese spurdog; Togari-tsunozame (Japanese)

Squalus japonicus Ishikawa 1908: 71-73 (original description; not illustrated; type locality: Sagami Bay and Kagoshima, Japan; three syntypes cited and deposited in the Imperial Museum of Tokyo are considered lost: ZUMT uncatalogued, juvenile male, unknown TL, adult male, 700 mm TL, female, unknown TL); Chen et al. 1979: 26-42 (re-description; Japan); Parin 1987: 48-49 (cited; Japan); Compagno and Niem 1998: 1222, 1229 (listed, cited; Western North and Central Pacific Ocean); Zhu and Meng 2001: 311, 316-317 (cited, description; Northwest Pacific Ocean); Nakabo 2002: 155 (listed; Ryukyu Islands, Okinawa Trough, Southern Japan); Compagno et al. 2005a: 75-76 (description; Northwest Pacific Ocean); Ward et al. 2007: 118, 123, 129, 130 (cited; Taiwan); Naylor et al. 2012: 58 (cited; Taiwan); Nakabo 2013: 194 (listed; Ryukyu Islands, Okinawa Trough, Southern Japan); Straube et al. 2013: 264-265 (cited; Taiwan); Shinohara et al. 2014: 233 (cited; Japan).

Squalus suckleyi : Fowler 1941: 259 (listed; Japan).

Neotype.

NSMT-P 44380, adult male, 645 mm TL, Senoumi Bank, Suruga Bay, Honshu, Japan, approximate coordinates 34°43'N and 138.33E, 270-300 m depth. Collected on 13 April 1982, collector Kazunari Yano.

Additional material.

CSIRO H 6294-26, juvenile male, 440 mm TL, Tashi fish market, near I-Lan (NE coast), Taiwan; CSIRO H 6294-27, juvenile female, 360 mm TL, locality same as CSIRO H6294-26; CSIRO H 6294-31, adult female, 540 mm TL, locality same as CSIRO H6294-26; HUMZ 40026, juvenile male, 215 mm TL, unknown locality; HUMZ 80223, adult male, unknown TL, near Okinawa, Japan, 25°33.8'N, 126°25.2'E, 310 m depth; HUMZ 95213, unknown sex and TL, East China Sea, 27°46'N, 126°15.3'E, 296-465 m depth; HUMZ 189642, adult male, 530 mm TL, East China Sea; HUMZ 189673, juvenile female, 430 mm TL, East China Sea; HUMZ 189675, juvenile female, 277 mm TL, East China Sea; HUMZ 189676, juvenile male, 288 mm TL, East China Sea; HUMZ 189678, adult male, 545 mm TL, East China Sea; HUMZ 189682, juvenile male, 365 mm TL, East China Sea; HUMZ 189685, adult female, 512 mm TL, East China Sea; HUMZ 189687, juvenile male, 380 mm TL, East China Sea; HUMZ 189689, juvenile male, 276 mm TL, East China Sea; HUMZ 189693, juvenile female, 380 mm TL, East China Sea; HUMZ 189695, juvenile female, 290 mm TL, East China Sea; HUMZ 189696, juvenile male, 291 mm TL, East China Sea; HUMZ 189701, juvenile male, 287 mm TL, East China Sea; HUMZ 189705, juvenile male, 282 mm TL, East China Sea; HUMZ 189735, adult male, 518 mm TL, East China Sea; HUMZ 189737, adult male, 560 mm TL, East China Sea; HUMZ 189738, adult male, 535 mm TL, East China Sea; HUMZ 189739, adult male, 530 mm TL, East China Sea; HUMZ 191688, juvenile female, 340 mm TL, Okinawa, Japan; HUMZ 191689, juvenile male, 281 mm TL, Okinawa, Japan; HUMZ 191691, juvenile male, 338 mm TL, Okinawa, Japan; HUMZ 191693, juvenile female, 410 mm TL, Okinawa, Japan; HUMZ 191694, juvenile female, 440 mm TL, Okinawa, Japan; HUMZ 191695, juvenile male, 338 mm TL, Okinawa, Japan; HUMZ 191697, juvenile female, 330 mm TL, Okinawa, Japan; HUMZ 191698, juvenile male, 388 mm TL, Okinawa, Japan; HUMZ 191699, juvenile female, 410 mm TL, Okinawa, Japan; NMMB P 15491, adult male, 593 mm TL, Pingtung county, Taiwan; NMMB P 15691, adult male, 540 mm TL, locality same as NMMB P 15491; NMMB P 15696, adult male, 580 mm TL, locality same as NMMB P 15491; NMMB P 15698, juvenile female, 448 mm TL, locality same as NMMB P 15491; NMMB P 15699, adult male, 513 mm TL, locality same as NMMB P 15491; NMMB P 15700, juvenile female, 443 mm TL, locality same as NMMB P 15491; NSMT-P 47384, juvenile female, 433 mm TL, Central Pacific Ocean; NSMT-P 67530, adult female, 560 mm TL, East China Sea, 31°21.31'N, 128°19.12'E, 254-260 m depth; NSMT-P 91127, juvenile female, 410 mm TL, Mimase Fishing Port, Kochi City, Kochi Prefecture, Shikoku, Japan; UF 44332, adult female, 490 mm TL, Seno-Umi, Honshu Island, Suruga Bay, Japan, 195 m depth.

Diagnosis.

Single value corresponds to neotype and range values include all examined material from which data was taken. Species of Squalus clearly distinct from all its congeners (except with S. melanurus Fourmanoir, 1979 and S. nasutus ) by a combination of characters: snout obtuse at tip and conspicuously elongate (prenarial length 5.9%-6.8% TL in adults); mouth markedly narrow, its width 1.6, 1.0-1.6 times prenarial length; pectoral fins conspicuously tapered (pectoral-fin posterior margin length 8.6%, 7.8%-9.2% TL in adults); markedly elongate preoral length 10.7%, 10.7%-12.2% TL. Squalus japonicus is differentiated from its regional congeners S. mitsukurii , S. brevirostris , S. shiraii sp. nov. and S. acutirostris by head markedly tapered with head width at mouth 9.7%, 9.7%-10.6% TL (vs. 10.9%-12.2% TL for S. mitsukurii vs. 10.7%-12.1% TL for S. brevirostris vs. 11.2%-11.6% TL for S. shiraii sp. nov. vs. 10.7%-11.6% TL for S. acutirostris ) and caudal fin with conspicuous black caudal bar and black upper caudal blotch (vs. black caudal bar and black upper caudal blotch absent). It is separated from S. brevirostris and S. shiraii sp. nov. by more elongate pre-first dorsal length (31.8%, 31.8%-33.0% TL vs. 29.6%, 28.9%-31.7% TL for S. brevirostris and 30.5%, 29.9%-31.2% TL for S. shiraii sp. nov.), larger preorbital length (8.7%, 8.7%-9.3% TL vs. 6.7%, 6.5%-7.5% TL for S. brevirostris vs. 7.9%, 7.4%-7.9% TL for S. shiraii sp. nov.) and from S. mitsukurii and S. shiraii sp. nov. by smaller first dorsal fin, its base length 6.7%, 6.6%-7.5% TL (vs. 8.2%, 7.6%-9.0% TL for S. mitsukurii vs. 7.7%, 7.7%-8.7% TL for S. shiraii sp. nov.). It is also distinct from S. mitsukurii by larger inner nostril-labial furrow space (4.6%, 4.6%-5.1% TL vs. 4.3%, 3.9%-4.5% TL for S. mitsukurii ) and from S. brevirostris by larger internarial space (4.1%, 4.1%-4.7% TL vs. 3.6%, 3.4%-3.8% TL for S. brevirostris ). It differs from S. shiraii sp. nov. by lower first dorsal fin, its height 6.6%, 6.6%-7.5% TL (vs. 8.1%, 7.9%-8.2% TL for S. shiraii sp. nov.) and lower number of precaudal and total vertebrae (87, 80-88 and 116, 104-116 vs. 93, 91-94 and 122, 120-123 for S. shiraii sp. nov.). Squalus japonicus also differs from S. brevirostris by dermal denticles tricuspidate, pectoral-fin free rear tips rounded, postventral caudal margins not uniformly white (vs. unicuspid dermal denticles, pectoral-fin free rear tips pointed, postventral caudal margins uniformly white).

Description

. Single values correspond to the neotype and ranges to all other examined material from which data were obtained.

External morphology. Medium sized species (512-645 mm maximum TL in adults), with body fusiform and skinny, somewhat arched from trunk to abdomen, turning slim to caudal fin; head height 0.9 (0.8-1.1) times trunk and abdomen heights (Fig. 4A-C ). Head compressed and very narrow, its width 1.2 (1.1-1.3) times trunk width and 1.3 (1.0-1.7) times broader than abdomen width; head elongate, its length 23.6% (23.0%-24.5% TL). Snout conical and obtuse at the tip, conspicuously elongate (preorbital length 9.4%, 8.3%-10.1% TL); anterior margin of nostrils bi-lobed with first lobe larger than second lobe; nostrils much closer to the mouth than to the tip of the snout, its prenarial length 1.4 (1.2-1.6) times the distance from nostril to upper labial furrow (Fig. 4D, E ). Eyes oval with anterior margin convex and posterior margin notched; eyes elongate, its length 2.5 (2.0-3.5) times greater than its height. Prespiracular length 0.6 (0.6-0.7) times prepectoral length. Spiracles crescent, placed laterally just posterior to the eyes; spiracles small, its length 0.3 (0.2-0.4) times eye length. Prebranchial length 1.4 (1.4-1.5) times larger than prespiracular length. Gill slits convex, located anterior to origin of pectoral fins; gill slits vertical and low with height of fifth gill slit 1.2 (0.9-1.6) times height of first gill slit.

Preoral length 1.8 (1.4-2.7) times greater than mouth width. Mouth markedly arched and narrow, its width 1.5 (1.0-1.6) times broader than internarial width and 1.0 (0.6-1.3) times prenarial length; upper labial furrow elongate, its length 2.1% (1.9%-2.4% TL), with fold very thin; lower labial furrow also elongate, although without fold. Teeth unicuspid and tiny on both jaws, although upper teeth smaller than lower teeth; cusp short and oblique, thicker on lower teeth than upper teeth; mesial cutting edge convex; mesial heel markedly notched; distal heel rounded; apron thick and short, somewhat conical in lower teeth (Figs 3E-F ). Two series of functional teeth on each jaw; 13-0-13 teeth rows for neotype (13-0-13 for other material) in upper jaw; 10-0-10 (11-0-11) teeth rows in lower jaw.

Pre-first dorsal length 1.4 (1.3-1.5) times larger than prepectoral length. Origin of first dorsal fin prior to the vertical line traced at pectoral-fin free rear tips. First dorsal fin evidently slender at fin web (broader in young juveniles); first dorsal-fin anterior margin convex; first dorsal-fin posterior margin almost straight, although falcate distally; first dorsal-fin apex markedly rounded; first dorsal-fin free rear tip pointed (Fig. 4F ); first dorsal fin short, its base length 1.0 (0.8-1.1) times height of first dorsal-fin, its length 1.0 (0.8-1.1) times length of second dorsal fin; first dorsal fin low, its height 1.3 (1.1-1.6) times length of first dorsal-fin inner margin; first dorsal-fin inner margin small, its length 5.6% (5.1%-6.6%) TL. First dorsal-fin spine narrow, its base width 0.6% (0.5%-0.8%) TL and very short (its length 2.9%, 2.0%-3.5% TL), comprising 0.4 (0.3-0.5) times first dorsal-fin height. Interdorsal space 1.0 (0.8-1.1) times prepectoral length and 2.2 (1.8-2.4) times larger than dorsal caudal space. Pre-second dorsal length 2.7 (2.6-2.8) times prepectoral length. Second dorsal fin slender at fin web; second dorsal-fin anterior margin concave; second dorsal-fin posterior margin concave and deeply falcate; second dorsal-fin apex rounded and lobe-like; second dorsal-fin free rear tip pointed (Fig. 4G ); second dorsal fin short, its length 2.1 (1.8-2.5) times second dorsal-fin height; second dorsal-fin inner margin small, its length 5.0% (4.3%-5.5%) TL; second dorsal fin low, its height 1.3 (1.2-1.4) times length of second dorsal-fin inner margin. Second dorsal-fin spine slender, its base width 0.8% (0.7%-1.0%) TL; second dorsal-fin spine small, its length 4.9% (4.1%-5.6%) TL, corresponding to 0.8 (0.6-1.0) times height of second dorsal fin, almost reaching its apex; second dorsal-fin spine 1.7 (1.3-2.2) times larger than first dorsal-fin spine.

Pectoral fins conspicuously narrow (pectoral-fin posterior margin length 7.9%, 6.8%-10.1% TL); pectoral-fin anterior and inner margins convex; pectoral-fin posterior margin concave (deeply concave in juveniles); pectoral-fin anterior margin length 1.6 (1.4-1.7) times length of pectoral-fin posterior margin and 1.5 (1.3-1.7) times length of pectoral-fin inner margin; pectoral-fin apex and free rear tips rounded; pectoral-fin free rear tips lobe-like and reaching the horizontal line traced at pectoral-fin apex (in juveniles, pectoral-fin free rear tips transcend the pectoral-fin apex) (Fig. 4H ). Pectoral-pelvic space 0.8 (0.7-0.8) times pelvic-caudal space. Pelvic-caudal space 1.2 (1.1-1.4) times larger than interdorsal space; pelvic fins in the midline between two dorsal fins, slightly nearer to first dorsal fin. Pelvic fins narrow with margins straight; pelvic-fin free rear tips pointed; pelvic fins short, its length 10.8% (9.6%-12.4%) TL. Clasper thin and small, slightly transcending pelvic-fin free rear tips; clasper inner margin length 0.8 (0.5-1.3) times length of pelvic inner margin; clasper groove dorsal and longitudinal, elongate and open; apopyle rounded, located anteriorly in the clasper groove; hypopyle constricted, located posteriorly in the clasper groove; rhipidion very thin and soft, flap-like, placed medially at distal end of the clasper.

Caudal keel prominent and lateral since insertion of second dorsal fin to behind origin of caudal fin. Caudal fin small with dorsal caudal margin length 0.9 (0.8-0.9) times head length and 1.9 (1.8-3.1) times length of preventral caudal margin; dorsal and ventral caudal lobes slender (dorsal lobe rectangular in juveniles); dorsal caudal tip pointed; dorsal caudal margin slightly convex; upper postventral caudal margin straight; lower postventral caudal margin convex (Fig. 4I ); preventral caudal margin convex and short, its length 2.0 (1.4-2.4) times greater than length of pelvic-fin inner margin; ventral caudal tip rounded; caudal fork discontinuous, markedly concave and narrow, its width 6.6% (6.0%-7.4%) TL.

Squamation (Fig. 7G, H ). Dermal denticles tricuspid and markedly imbricated, its length slightly greater than its width; denticles conspicuously broad at the crown base; cusps posterior, prominent and pointed; lateral cusps shorter than median cusp, forming well-marked concavity with median cusp; median ridge thick and elongate; one to two lateral ridges, very thin, almost equal in length to median ridge; anterior furrow shallow with one small ridge on each side; anterior margin of the crown arrow-shaped. In juveniles, denticles are slender at the crown base, with cusps conspicuously pointed and more elongate and anterior margin of the crown tapered.

Colouration (Fig. 4 ). Body grey to light grey dorsally and white laterally from insertion of pectoral fins to origin of caudal fin. Dorsal fins greyish, darker at its apex to the upper half of the posterior margin, whitish at fin base and free rear tips; dorsal-fin spine brown anteriorly, white posteriorly and at the tips. Pectoral fins grey, slightly darker near pectoral-fin anterior margin; pectoral-fin posterior margin strongly white and uniform. Pelvic fins grey dorsally and completely pale ventrally; pelvic-fin posterior margin white. Caudal fin mostly greyish, light grey over vertebral column; dorsal caudal margin whitish proximally; upper postventral caudal margin white, lower postventral caudal margin broadly white; lower caudal lobe mostly white; preventral caudal margin whitish; black caudal stripe conspicuous; black upper caudal blotch conspicuous in the upper caudal lobe, nearest to dorsal caudal tip; black caudal bar oblique, placed in the caudal fork to midline of upper postventral caudal margin; dorsal and ventral caudal tips broadly white. Embryos, neonates and young juveniles exhibit body light grey with caudal bar and upper caudal blotch more conspicuous than in adults.

Vertebral counts (Table 6 ). 87 (neotype) 80-88 (other material) precaudal vertebrae; 73 (65-75) diplospondylous vertebrae; 115 (104-116) total vertebrae.

Geographical distribution.

Squalus japonicus is a regional endemic species occurring in the North-western Pacific Ocean from Southern Japan, China to Taiwan (Fig. 8C ). It is found on the upper continental slope of tropical and subtropical areas, ranging between 195-520 m depth, although it also has been reported at 52 m depth only in Weigmann (2016). This species also occurs in Korean waters ( Chen et al. 1979).

Remarks.

Ishikawa (1908) mentioned three syntypes of S. japonicus that were deposited at the Zoological University Museum of Tokyo (formerly Imperial Museum of Tokyo). A visit to the fish collection from ZUMT was undertaken in 2013 to verify the existence of the type material. However, it was noticed that there was a single specimen of S. japonicus held in the museum, assuming that syntypes are lost and no longer exist. Dr. M. Nakae (NSMT, person. comm. 2014) stated that the NSMT fish collection has never been in possession of this material and ratified that the syntypes are lost. Squalus japonicus has been misidentified in waters outside Japan (e.g. Vietnam by Quang et al. 2013) and many morphological variations were reported earlier in Compagno et al. (2005b) and Last et al. (2007b) for material from Indonesia, Philippines and Western Australia, compromising the correct application of this nominal species. To clarify the taxonomic status of S. japonicus across the Western Pacific Ocean, the designation of a neotype along with a re-description of this species is provided herein. The neotype was collected from Southern Japan (Senoumi Bank, Suruga Bay), which is within the known range distribution of S. japonicus , based on the examined material, the original description of S. japonicus and information in literature. The designation of the neotype was further based on the sex, maturity and total length that were approximate to those provided for a syntype of S. japonicus in Ishikawa (1908). The neotype is securely deposited in the scientific fish collection from the NSMT in Tokyo at the Department of Zoology for preservation and accessibility purposes. This species is easily separated from its congeners through many characteristics of the external morphology, morphometrics and meristic data, including shape of head, snout and pectoral fins, length of snout, width of mouth and preoral length and several other external measurements as shown in the diagnosis above. The current diagnosis and re-description of S. japonicus are congruent with observations of Ishikawa (1908) and Chen et al. (1979) with the exception of the presence of two hooks in the clasper. These cartilages of the clasper probably concern the accessory terminal 3 cartilage (spur) and dorsal terminal cartilage (claw) that are commonly noticed in species of Squalus . Differences in morphometrics are observed between the data provided in Ishikawa (1908) and those from the present analysis, but this is due to divergences of the applied methodology.

This species together with S. melanurus and the Australian species S. nasutus , comprise the S. japonicus subgroup of species whose members are characterised by having a conspicuously elongate and obtuse snout, thin body, mouth very narrow and pectoral fins tapered ( Viana and Carvalho 2018a). The Japanese species is more closely related to S. nasutus according to morphological and genetic data ( Last et al. 2007b). Shape of dermal denticles, dentition and shape of dorsal, pectoral, pelvic and caudal fins are intrinsically similar between these two species. Morphometrics are also mostly congruent, although differences in measurements are apparent when adults are compared: second dorsal fin height 5.4%-6.5% TL for S. japonicus vs. 4.9%-5.3% TL for S. nasutus ; length of second dorsal-fin anterior margin 10.8%-12.7% TL vs. 8.6%-10.5% TL; length of second dorsal-fin spine 4.7%-5.6% TL vs. 3.9%-4.4% TL; length of dorsal caudal margin 19.6%-20.4% TL vs. 18.1%-19.4% TL. Preoral length, eye length, pectoral-fin inner margin length, trunk height and width overlaps between these two species which contradicts Last et al. (2007b) in supporting these measurements as diagnostic characters for these species. Vertebral counts differ between S. japonicus and S. nasutus as well: monospondylous (41-43), precaudal (84-88) vertebrae (vs. 37-40; 80-83 for those from Australia). These results are congruent with recent molecular analyses of the cytochrome c oxydase 1 (COI) and NADH dehydrogenase 2 (NAD2) mitochondrial genes in Ward et al. (2007), Naylor et al. (2012), Straube et al. (2013), Veríssimo et al. (2017) and Daly-Engel et al. (2018) which support genetic divergence between S. japonicus and S. nasutus . The latter study also noticed high intraspecific genetic distances in S. japonicus when including data taken from populations from Japan and Taiwan, but variations in the species are not yet supported through morphological evaluation, except for the black caudal marking near the base of the lower lobe in Taiwanese specimens that is absent in other material. Compagno et al. (2005b) also noticed variations in this species when examining material from the Philippines and considered it to be a separated species ( Squalus sp. 2) due to differences with S. japonicus and S. nasutus . In contrast, Last et al. (2007b) considered it to be con-specific with S. nasutus as the morphological differences pointed in Compagno et al. (2005b) and in their study represent intraspecific variations. Whether the Philippine form represents an undescribed species is still unclear, but we consider it here to be con-specific with S. nasutus for nomenclature stability.

Comparative material.

Squalus nasutus . AMS I22817-008, juvenile male, 362 mm TL, Northwest Shelf, 240 km north of Port Hedland, Western Australia, 18°06'S, 117°45'E, 492-520 m depth; CSIRO H 4132-02, adult male, 465 mm TL, Bolinao evening market, Philippines; CSIRO H 4132-03, juvenile female, 475 mm TL, locality same as CSIRO H 4132-02; CSIRO H 4132-04, adult female, 540 mm TL, locality same as CSIRO H 4132-02; CSIRO H 5860-01, adult female, 540 mm TL, Cilacap (South coast, central Java), Indonesia, 07°40'S, 109°00'E; CSIRO H 5860-02, adult female, 570 mm TL, locality same as CSIRO H 5860-01; CSIRO H 5860-03, adult female, 545 mm TL, locality same as CSIRO H 5860-01; CSIRO H 6125-04, adult male, 465 mm TL, Kedonganan, Jimbaran Bay (South coast of Bali), Indonesia, 08°45'S, 115°10'E; CSIRO H 6413-01, adult female, 580 mm TL, West of Shark Bay, Western Australia, 25°03.8'S, 112°08.9'E, 315-340 m depth; CSIRO H 6484-01, adult female, 575 mm TL, locality same as CSIRO H 5860-01. Type material of S. nasutus : CSIRO H2590-12, adult female, 503 mm TL, west of Leander Point, Western Australia, 29°15'S, 113°56'E (holotype); Paratypes: CSIRO H 2608-15, juvenile female, 411 mm TL, Rottnest Canyon, Western Australia, 31°57'S, 115°08'E ; CSIRO H 2598-07, juvenile female, 465 mm TL, west of Green Head, Western Australia, 29°58'S, 114°27'E ; CSIRO H 2567-08, adult male, 470 mm TL, west of Dorre Island, Western Australia, 25°09'S, 112°09'E ; CSIRO H 1652-01, juvenile female, 315 mm TL, northwest of Port Hedland, Western Australia, 18°25'S, 117°48'E; CSIRO H 1652-02, juvenile female, 459 mm TL, same locality as CSIRO H 1652-01; CSIRO H 1207-07, adult female, 537 mm TL, northwest of Port Hedland, Western Australia, 18°20'S, 117°50'E; CSIRO H 1207-08, juvenile female, 496 mm TL, same locality as CSIRO H 1207-07; CSIRO CA 3290, adult female, 549 mm TL, southwest of Rowley Shoals, Western Australia, 18°10'S, 118°20'E; CSIRO CA 4055, adult female, 527 mm TL, southwest of Rowley Shoals, Western Australia, 18°11'S, 118°04'E ; CSIRO H 2898-07, juvenile male, 452 mm TL, north-northwest of Port Hedland, Western Australia, 18°07'S, 118°12'E; CSIRO CA 4110, adult male, 497 mm TL, east of Rowley Shoals, Western Australia, 17°18'S, 120°09'E ; CSIRO H 1693-01, juvenile male, 361 mm TL, Rowley Shoals, Western Australia, 17°02'S, 120°05'E; CSIRO H 1693-02, juvenile female, 306 mm TL, same locality as CSIRO H 1693-01; CSIRO H 1694-01, juvenile female, 425 mm TL, Rowley Shoals, Western Australia, 16°57'S, 120°14'E ; CSIRO H 2032-01, adult male, 461 mm TL, northeast of Mermaid Reef, Rowley Shoals, Western Australia, 16°54'S, 120°25'E; CSIRO H 2032-02, juvenile female, 404 mm TL, same locality as CSIRO H 2032-01; WAM P 28086-006, juvenile male, 380 mm TL; juvenile female, 450 mm TL, Rowley Shoals, Western Australia, 17°49'S, 118°41'E, 308-310 m depth.

Figures

Figure 3. Upper (A, C, E, G, I) and lower (B, D, F, H, J) teeth of S. shiraii sp. nov. (A, B; HUMZ 80329), S. mitsukurii (C, D; HUMZ 33680), S. japonicus (E, F; HUMZ 189737), S. brevirostris (G, H; HUMZ 189762) and S. suckleyi (I, J; NSMT-P 92640). Scale bars: 1 mm.

Figure 4. Squalus japonicus: lateral (A-C) and ventral (D, E) views; first (F) and second (G) dorsal fins; pectoral (H) and caudal (I) fins. NSMT-P 44380 (neotype), adult male, 645 mm TL (A, D, F-I); HUMZ 189738, adult male, 535 mm TL (B); HUMZ 189687, juvenile male, 380 mm TL (C, E). Scale bars: 50 mm (A-E); 20 mm (F-I).

Figure 7. Scanning electron microscopy of the dermal denticles. Squalus shiraii sp. nov. (A, B): HUMZ 149389 (holotype), adult male, 590 mm TL. S. formosus (C, D): CSIRO H- 6816 - 01 (holotype), adult male, 720 mm TL. S. mitsukurii (E, F): HUMZ 102987, adult male, 970 mm TL. S. japonicus (G, H): NSMT-P 44380 (neotype), adult male, 645 mm TL (G); NSMT-P 91127, juvenile female, 410 mm TL (H). S. brevirostris (I, J): NSMT-P 47378, adult female, 600 mm TL (I); KAUM-I 187, adult female, 578 mm TL (J). S. suckleyi (K, L): NSMT P- 92640, adult female, 970 mm TL. Scale bars: 50 μm (B); 100 μm (D, F, L); 200 μm (A, C, E, G-K).

Figure 8. Map of the North-western Pacific Ocean, showing the geographical distribution of Squalus species. A: S. shiraii sp. nov. (red); B: S. mitsukurii (orange); C: S. japonicus (brown); D: S. brevirostris (yellow); E: S. acutirostris (green); F: S. suckleyi (pink). Star: holotype / neotype; Dotted circle: paratypes; Circle: other material.