Stolephorus grandis, Hata & Motomura, 2021

Hata, Harutaka & Motomura, Hiroyuki, 2021, Stolephorus grandis, a new anchovy (Teleostei: Clupeiformes: Engraulidae) from New Guinea and Australia, Zootaxa 5004 (3), pp. 481-489 : 482-488

Stolephorus grandis n. sp.

[New English name: Papuan Double-lined Anchovy]

Figure 1 ; Tables 1–3

urn:lsid:zoobank.org:pub:8C56370C-17C9-483A-973E-777C6553BB93

Holotype. RMNH. PISC. 24670, 102.9 mm SL, Merauke , Papua, Indonesia, 5 Apr. 1955.

Paratypes. 9 specimens, 59.2–116.1 mm SL: AMS-I. 22777-006, 59.2 mm SL, south end of Ellis Beach , north of Queensland, Cairns, Australia (16°43′48″S, 145°39′00″E); RMNH. PISC. 84311, 116.1 mm SL, collected with the holotype; KAUM –I. 156158, 82.6 mm SL, NSMT-P 140585 , 80.5 mm SL, NTM S. 10071-001 , 5 specimens, 77.7–88.0 mm SL, Van Diemen Gulf, Northern Territory, Australia .

Diagnosis. A species of Stolephorus with the following combination of characters: maxilla rather short, 16.7– 18.2% SL (mean 17.5%), its posterior tip slightly short of, or reaching to, or slightly beyond posterior margin of preopercle; mandible short, 14.3–15.3% SL (14.7%); posterior margin of preopercle convexly rounded (not indented); no predorsal scute; prepelvic scutes 3–6 (modally 4); pelvic scute without spine; gill rakers 14–16 (16) in upper series on first gill arch, 21–23 (23) in lower series, 35–39 (39) in total; gill rakers 10–12 (11) in upper series on second gill arch, 18–20 (20) in lower series, 28–32 (30) in total; gill rakers 8–9 (9) in upper series on third gill arch, 10–12 (11) in lower series, 18–21 (20) in total; gill rakers 7 or 8 (8) in upper series on fourth gill arch, 9–10 (9) in lower, 16–18 (17) in total; gill rakers 3–5 (5) on posterior face of third gill arch; transverse scales 8; pseudobranchial filaments 20–27 (22); paired dark patches on parietal and occipital regions; double dark lines on dorsum from occipital region to dorsal-fin origin but absent behind dorsal-fin base; no black spots on suborbital area and tip of lower jaw; head rather short, 22.0–24.0% SL (mean 23.0%), postorbital length 11.5–12.4% SL (11.9%); caudal peduncle long, 21.9–23.7% SL (22.8%); pelvic fin relatively short, 8.3–9.0% SL (8.6%), depressed pelvic fin not reaching posteriorly to vertical through dorsal-fin origin; distance from snout to pectoral-fin insertion 25.0–27.0% SL (25.6%); distance from snout to pelvic-fin insertion 42.8–44.4% (43.3%); dorsal-fin base short, 12.6–14.8% SL (13.9%); anal-fin base short, 16.0–17.8% SL (16.9%); third dorsal-fin ray short, 14.8–15.7% SL (15.3%); third analfin ray short, 11.9–13.8% (12.5%); vertebral count 21 or 22 (modally 21) + 21 or 22 (21) = 42 or 43 (42).

Description. Data for holotype presented first, followed by data for non-type specimens in parentheses (if different). Counts and measurements, expressed as percentages of SL or HL, given in Tables 1 and 2. Body laterally compressed, elongate, deepest at dorsal-fin origin. Dorsal profile of head and body slightly convex from snout tip to dorsal-fin origin, gently lowering to uppermost point of caudal-fin base. Ventral profile of head and body slightly convex from lower-jaw tip to pelvic-fin insertion, thereafter slowly rising to lowermost point of caudal-fin base. Abdomen somewhat rounded, covered with four (three to six) spine-like scutes. Pelvic scute without spine. Postpelvic and predorsal scutes absent. Anus just anterior to anal-fin origin. Snout tip rounded; snout length less than eye diameter. Mouth large, inferior, ventral to body axis, extending backward beyond posterior margin of eye. Maxilla rather long, its posterior tip pointed, just reaching (short of or slightly beyond) to posterior margin of preopercle. Lower jaw slender. Single row of conical teeth on each jaw and palatines. Several distinct conical teeth on vomer. Teeth patch on pterygoid. A few fine teeth on upper edge of hyoid. Several rows of conical teeth on upper edges of basihyal and basibranchial. Eye large, round, covered with adipose eyelid, positioned laterally on head dorsal to horizontal through pectoral-fin insertion, visible in dorsal view. Pupil round. Orbit elliptical. Nostrils close to each other, anterior to orbit. Posterior margin of preopercle convexly rounded (not indented). Subopercle and opercle with smoothly rounded posterior margins. Gill membrane without serrations. Interorbital space flat, width less than eye diameter. Pseudobranchial filaments present, length of longest filament shorter than eye diameter. Gill rakers long, slender, rough, visible from side of head when mouth opened. Single row of asperities on anterior surface of gill rakers. Isthmus muscle long, reaching anteriorly to posterior margin of gill membranes. Urohyal hidden by isthmus muscle (not visible without dissection). Gill membrane on each side joined distally, most of isthmus muscle exposed (not covered by gill membrane). Scales cycloid, thin, deciduous, except for prepelvic scutes. Head scales absent. Lateral line absent. Fins scaleless, except for broad triangular sheath of scales on caudal fin. Dorsal-fin origin posterior to vertical through base of last pelvic-fin ray, slightly posterior to middle of body. Dorsal and anal fins with three anteriormost rays unbranched and closely spaced. First dorsal- and anal-fin rays minute. Anal-fin origin just below base of twelfth (ninth to twelfth) dorsal-fin ray. Posterior tip of depressed anal fin not reaching caudal-fin base. Uppermost pectoral-fin ray unbranched, inserted below midline of body. Posterior tip of pectoral fin not reaching to pelvic-fin insertion. Dorsal, ventral, and posterior margins of pectoral fin nearly linear. Pelvic fin shorter than pectoral fin, insertion anterior to vertical through dorsal-fin origin. Posterior tip of depressed pelvic fin not reaching to vertical through dorsal-fin origin. Caudal fin forked, posterior tips pointed.

Coloration of preserved specimens. Body uniformly pale. Silver longitudinal band running from just behind upper opercular margin to caudal-fin base. Cheek and opercle silver. Scattered melanophores on snout tip, absent on suborbital area. Paired dark patches on parietal and occipital regions. Double dark lines on dorsum from occipital area to dorsal-fin origin. Scale pockets on dorsum with black posterior margin. All fins whitish, semi-transparent. Melanophores distributed along fin rays of dorsal and caudal fins. Caudal fin with black posterior margin.

Distribution. Currently known only from the southern coast off Merauke, Papua, Indonesia to the northern coast of Australia (from Van Diemen Gulf, Northern Territory to Cairns, Queensland) ( Fig. 2 ).

Etymology. The specific name “grandis” refers to the larger body of the species, compared with similar species.

Remarks. The new species is assignable to the genus Stolephorus , as defined by Whitehead et al. (1988) and Wongratana et al. (1999), in having a long isthmus muscle reaching anteriorly to the posterior margin of the gill membrane, the urohyal covered by the isthmus muscle, and prepelvic scutes, in addition to the absence of postpelvic scutes. Stolephorus grandis is easily distinguishable from all congeners, except for Stolephorus mercurius Hata, Lavoué & Motomura, 2021 , Stolephorus multibranchus Wongratana, 1987 , and Stolephorus rex Jordan & Seale, 1926, in having double pigmented lines on the dorsum from the occipital area to the dorsal-fin origin, a long maxilla (posterior tip just reaching or slightly beyond the preopercle posterior margin), and lacking a predorsal scute ( Whitehead et al., 1988; Wongratana et al., 1999; Kimura et al., 2009; Hata & Motomura, 2018a –d, 2021; Hata et al., 2019, 2020a, b, 2021; Gangan et al., 2020). Moreover, the new species differs from the latter three species in having fewer gill rakers [total gill rakers on first, second, third, and fourth gill arch 35–39, 28–32, 18–21, and 16–18, respectively in S. grandis vs. more than 38, 31, 20, and 15 (more than 18 in S. mercurius and S. multibranchus ), respectively in the other three; Table 1; Fig. 3 ], more total vertebrae (42 or 43 vs. 40 or fewer; Tables 1, 3), a longer caudal peduncle (21.9–23.7% SL vs. shorter than 20.8%), and the depressed pelvic fin not reaching posteriorly to vertical through the dorsal-fin origin (vs. reaching posteriorly beyond vertical through dorsal-fin origin). Furthermore, the relative length of the pelvic fin separates S. grandis , S. mercurius , and S. multibranchus (pelvic-fin lengths 8.3–9.0% SL, 9.1–11.1%, and 10.0–11.9%, respectively). Lengths of both jaws and the head also separate S. grandis , S. multibranchus , and S. rex (lengths of maxilla, mandible, and head 16.7–18.2% SL, 14.3–15.3% SL, and 22.0–24.0% SL, respectively, in S. grandis vs. 18.0–21.1%, 16.0–18.5%, and 24.8–26.7%, respectively, in S. multibranchus , and 19.1–23.1%, 16.1–18.3%, and 24.3–27.6%, respectively, in S. rex ). Additionally, S. grandis is further distinguished from S. rex by its shorter postorbital length (11.5–12.4% SL in S. grandis vs. 12.6–14.9% in S. rex ) ( Hata & Motomura, 2018c; Hata et al., 2021; this study), and from S. multibranchus by its shorter dorsal- (12.6–14.8% SL vs. 14.0–16.1%) and anal-fin bases (16.0–17.8% SL vs. 18.3–21.3%) ( Table 2; Fig. 4 ; Hata & Motomura, 2018c; Hata et al., 2021; this study). Additionally, the other three species ( S. mercurius , S. multibranchus , and S. rex ) have never been recorded from New Guinea and Australia, where the new species occurs.

Comparative material examined. Stolephorus mercurius (28 specimens, 62.3–103.6 mm SL) and Stolephorus rex (45 specimens, 57.3–104.4 mm SL): listed in Hata et al. (2021). Stolephorus multibranchus (17 specimens, 45.9–71.2 mm SL): listed in Hata & Motomura (2018c).

Figures

FIGURE 1. (A) Lateral view of body and (B) dorsal view of head of the holotype of Stolephorus grandis n. sp. (RMNH. PISC.24670, 102.9 mm SL, Merauke, Papua, Indonesia).

FIGURE 2. Distributional records of Stolephorus grandis, based on specimens examined in this study. Star indicates the type locality.

FIGURE 3. Relationships of total gill-raker numbers (TGR) on (A) first gill arch (1GA), (B) second gill arch (2GA), (C) third gill arch, and (D) fourth gill arch, relative to standard length in Stolephorus grandis n. sp. (circles), S. mercurius (triangles), S. multibranchus (diamonds), and S. rex (squares).

FIGURE 4. Morphometrics of Stolephorus grandis n. sp. (circles), S. mercurius (triangles), S. multibranchus (diamonds), and S. rex (squares) [all as % of SL versus standard length (SL)]: A, caudal-peduncle length B, pelvic-fin length; C, maxilla length; D, mandibular length; E, head length; F, postorbital length; G, dorsal-fin base length; and H, anal-fin base length.