Coelorinchus zinjianus, Prokofiev & Iwamoto, 2023

Prokofiev, Artem M. & Iwamoto, Tomio, 2023, A new Coelorinchus from the western Indian Ocean with comments on the C. tokiensis group of species (Teleostei: Gadiformes: Macrouridae), Zootaxa 5301 (1), pp. 137-150 : 138-144

Coelorinchus zinjianus sp. nov.

urn:lsid:zoobank.org:act:70D7425A-0B0F-4C81-A9B1-3E25C107B7DB

Figures 1 , 2 , 3A , 4A , 5A , 6A ; Tables 1 , 2

Holotype. IOM M.730-01, 220+ mm TL, 74 mm HL, R/ V Vityaz-II, cruise 17, sta. 2608, 12°28'– 12°25' S, 48°18'– 48°26' E, 480 m, bottom shrimp trawl 19.4 m, 02:25–04:10, 14 Nov. 1988.

Paratypes. IOM M.729, 117+ mm TL, 37+ mm HL, R/ V Rift, cruise 2, sta. 19, sample 24, 12°24' S, 48°26' E, 480–500 m, bottom trawl 30 m, 19:45–20:17, 11 Apr. 1983 . IOM M.730-02, 2 (152–174+ mm TL, 52–59 mm HL), collected with the holotype. IOM uncatalogued (currently on-loan to CAS), 2 (178–332+ mm TL, 54–103.5 mm HL), R/ V Vityaz-II, cruise 17, sta. 2645, 22°20.5' S, 43°03.6' E, 450–500 m, otter-trawl no. 40, 16:42–17:25, 02 Dec. 1988 .

Diagnosis. Long-snouted Coelorinchus with pointed diamond-shaped terminal snout scute, large mouth with thick lips and somewhat enlarged outer premaxillary teeth, premaxillary tooth band long, subopercular flap extended, underside of head and nasal fossa completely scaled, scales atop head with numerous diverging rows of spinules, flank scales with 6–9 rows of small depressed spinules in weakly diverging to almost parallel complete rows, external light organ forming narrow and elongate fossa in front of anus, 48 pyloric caeca; body with dark transverse bands, first dorsal fin black at base, pale distally; lips and mouth pale.

Description. General features of fish seen in Figure 1 . Counts: first dorsal-fin rays, ii + 8 [ii + 8–9]; pectoral-fin rays, i + 17 [i + 14–17]; pelvic-fin rays, 7; gill-rakers (inner) on 1 st arch, 8 [6–10]; gill-rakers on 2 nd arch, 7 (outer) [6–7] / 8 [6–9] (inner); transverse scale rows below origin of first dorsal fin, 4.5 [4.0–6.5]; transverse scale rows below midbase of first dorsal fin, 3.5 [3.0–4.0]; transverse scale rows below origin of second dorsal fin, 4.5 [4.0–5.5]; transverse scale rows between origin of anal fin and lateral line, 10 [10–12]; lateral-line scales before origin of second dorsal fin, 14 [14–15]; pyloric caeca, 48 (n = 1). Measurements shown in Table 1 . Width of body across pectoral-fin bases 67.7 % [63.5–76.4 %, but 100 % in smallest juvenile] of greatest body depth (at dorsal-fin origin), 1.2 [0.8–1.2] times smaller than greatest width of head (at preopercles). Head ca. 3.0 [2.9–3.3] times in TL. Snout long and sharply pointed, 2.1 [2.0–2.2] times in HL, 0.6 [0.5–0.7] times in postorbital length of head, with dorsal contour slightly concave in front of nostrils; sides in dorsal view strongly convergent toward terminal scute and slightly concave on short distance behind tip ( Fig. 2A–C ). Snout tipped with long, acute, attenuated terminal scute, 2.8 times longer than broad, sides almost parallel along posterior half ( Fig. 2B ). Anterolateral margins of snout not completely supported by bone. Orbit elliptical, 4.1 [4.1–4.5] times in HL, 2.0 [1.9–2.2] times in snout. Suborbital shelf sharply angulated; shelf depth 1.7 [1.7–2.1, but 1.5 in smallest juvenile] times in suborbital depth. Lateral nasal ridge 2.9 [2.7–3.4] times shorter than length of suborbital ridge. Mouth large, posterior tip of maxilla extending midway between hind margin of pupil and hind border of orbit, rictus extending below posterior third of pupil. Jaw teeth conical, in narrow bands somewhat broadened toward symphysis; outer row of premaxillary teeth somewhat enlarged; dentary teeth uniform in size, smaller than those on premaxilla. Premaxillary tooth band long, 1.3 [1.1–1.3] times in length of rictus, reaching below middle of pupil; dentary tooth band reaching rictus. Preopercle inclined backward at about 70º, with elongate posteroventral lobe having narrowly rounded distal tip and broadly rounded ventral margin. Subopercle terminates ventrally in slender tip level with distalmost tip of preopercle ( Fig. 3A ). Chin barbel moderately short, slender, 3.0 [2.7–3.8] times in orbit. Free neuromasts on head pale, minute, inconspicuous. Lips thick, finely papillose; upper lip fully covering outermost premaxillary teeth. Inner side of gill opening with weak bulge in its lower half.

TABLE 1. (Continued)

First dorsal-fin base 1.1 [1.1–1.5, but 2.2 in smallest juvenile] times longer than interdorsal space; second dorsal-fin spine apparently without filamentous tip. Pectoral fin narrow based, longest rays reaching well behind anal-fin origin. Pelvic-fin origin at vertical of first dorsal-fin origin or slightly in front of it, and on vertical of pectoral-fin base. Outermost pelvic-fin ray filamentous, ending just behind tip of adpressed pectoral fin. Anus close to anal-fin origin (less than one scale row). Light organ expressed externally as narrow and elongate fossa in front of anus ( Fig. 2D ), 2.0 [2.7–4.0] times shorter than pelvic-anal distance.

Flank scales moderately adherent in larger fishes, bearing 6–9 weakly diverging to almost parallel rows of sharp, needle-like to narrowly lanceolate spinules; spinules in rows strongly depressed, gradually increasing in length posteriad, connate at bases; all rows complete; medial row of spinules not enlarged ( Fig. 4A ). Posteriormost spinules in rows longer on tail scales. Lateral buttresses of spinules not developed. Predorsal scales with more erect spinules less connate at bases, arranged in 4–6 clearly diverging rows. Scales on isthmus with diverging rows of small, moderately depressed spinules connate at bases. Scales on top of head ( Fig. 6A ) with 3 to 6 diverging rows of sharp erect spinules, not connate at bases, slightly increasing in length posteriad. Supraoccipital scute small, as large as neighboring scales, coarsely spinulated, with radiating spinule rows. Postoccipital scute indistinguishable. Scales on cheek and opercle with 3–6 strongly diverging rows of small (mostly uniform in size), more or less raised spinules, not connate at base. Dorsal surface of snout, nasal fossa, and suborbital shelf fully scaled ( Figs. 2A, B , 5A ). Underside of head fully scaled except gular region and branchiostegal membranes ( Fig. 2C ); scales strongly adherent, bearing diverging rows of spinules. Scutes of head coarsely spinulated; scutes of medial nasal ridge 11 in number (including terminal scute), with diverging rows of spinules.

Body color in preservative ( Fig. 1 ) pale with up to 9 broad (about 6–10 scale rows wide) dark brown saddlelike bars reaching just below midlateral line; second, fourth, sixth, and seventh bars most conspicuous. First bar forms indistinct saddle between upper margins of gill cover. Second bar is situated below first dorsal-fin base, third (indistinct and short) in interdorsal space, fourth below origin of second dorsal fin, sixth at about midlength of tail. Basal half of first dorsal fin and bases of pelvic fins blackish; posteriormost portion of anal fin (from level of sixth transverse bar to end of tail) with blackish distal stripe; otherwise, fins pale; pelvic-fin filament pure white. Mouth, lips, gums, and branchiostegal membranes pale; underside of gill cover dark.

Etymology. The species is named from Zinj, an ancient Arabian name for East Africa and the nearby islands; adjective.

Figures

FIGURE 1. Coelorinchus zinjianus sp. nov., holotype, IOM M.730-01, lateral view. Scale bar: 30 mm.

FIGURE 2. Coelorinchus zinjianus sp. nov., holotype, IOM M.730-01: (A–C) head: (A) lateral view; (B) dorsal view; (C) ventral view; (D) light organ. Scale bars: (A–C) 30 mm (common bar), (D) 10 mm.

FIGURE 3. Coelorinchus spp., preopercular lobe and subopercular flap: (A) C. zinjianus sp. nov., holotype, IOM M.730-01; (B) C. quadricristatus, ZMMU P-12129; (C) C. flabellispinis, IOM M.174; (D) C. trunovi, IOM M.052-002. Scale bars: 10 mm.

FIGURE 4. Coelorinchus spp., flank scales (top: dorsal view; bottom: dorsolateral view): (A) C. zinjianus sp. nov., holotype, IOM M.730-01; (B) C. quadricristatus, ZMMU P-12129; (C) C. flabellispinis, IOM M.172; (D) C. trunovi, IOM M.052-002. Scale bars: 1 mm.

FIGURE 5. Coelorinchus spp., nasal fossa (dashed line shows boundary between the scaled and naked parts; anterodorsal border of nasal fossa [supranarial ridge] arrowed): (A) C. zinjianus sp. nov., holotype, IOM M.730-01; (B, C) C. quadricristatus: (B) ZMMU P-12129; (C) SAIAB 14867; (D) C. flabellispinis, IOM.172; (E) C. trunovi, IOM M.052-002. Scale bars: 5 mm.

FIGURE 6. Coelorinchus spp., scale cover atop of head: (A) C. zinjianus sp. nov., holotype, IOM M.730-01; (B–D) C. quadricristatus: (B, C) ZMMU P-12129, (C) isolated scale; (D) SAIAB 14867; (E) C. flabellispinis, IOM.172; (F) C. trunovi, IOM M.052-002. Scale bars: (A, B, E, F) 3 mm; (C) 1 mm; (D) 10 mm.

Tables

TABLE 1. Measurements of the species of the Coelorinchus flabellispinis group. Note: (?) character not measured; (n) number of specimens measured; abnormal measurements found in a single specimen are given in parentheses.

Character	Coelorinchus zinjianus sp. n.						C. quadricristatus			C. flabellispinis	C. trunovi
	Holotype	Paratypes					Syntype	CAS 50121, SAIAB	SAIAB 14867	(n = 20)	(n = 7)
		(* terminal snout scute worn at distal tip)						14087, ZMMU 12129 (n = 4) **(n = 2: CAS, ZMMU)	(n = 2)
Total length, mm	220+	332+	174+	178+	152+	117+	128+	136+–179+	515+–522+	119+–266+	147+–433
Head length, mm	74	103.5*	59	54*	52	37+	56.5	49–61	170–179	35–82	34–113
							In % HL
Snout length	48.7	48.8	50.9	47.9	48.1	46.0+	45.1	45.9–49.4	49.4–50.3	37.1–40.9 (~35.9)	36.8–41.3
Orbit diameter	24.3	22.1	22.9	24.0	23.1	24.3	21.8	20.0–22.4	18.9–19.4	24.4–28.8	22.1–28.9 (32.4)
Postorbital length	27.0	29.8	26.3	27.4	28.9	29.7	33.6	28.0–33.1	29.9–33.2	31.8–35.9 (37.1)	31.0–38.9
Orbit–preopercle length	33.8	35.4	30.5	36.0	31.7	29.7	34.5	29.0–33.4	32.1–33.9	28.3-32.9	31.0–39.8
Suborbital width	9.9	11.2	8.5	10.7	9.6	8.1	?	7.4–12.0	9.1–10.1	7.5–10.0 (6.7)	9.5–11.8
Suborbital-shelf width	5.8	5.5	5.1	5.2	5.3	5.4	?	4.9–7.0**	?	3.4–5.3	4.8–7.1
Upper-jaw length	25.0	27.8	24.6	21.8	25.0	24.3	25.8	21.0–26.2	26.9–27.1	24.4–28.1	28.6–31.9
Length of rictus	19.6	20.7	17.8	15.0	19.2	17.6	21.2	18.2–22.0	20.0–22.0	19.5–23.9	22.6–26.6
Length of premaxillary tooth band	15.5	15.6	16.1	12.9	16.4	13.5	?	14.0–15.6**	?	16.7–20.0	17.5–20.0 (23.1)
Preoral length	44.6	38.6	44.1	44.2	44.2	44.6	38.9	38.6–45.0	38.2–42.7	32.4–38.3	31.0–39.3
Length of terminal scute	9.5	6.8*	11.9	8.1*	9.6	damaged	?	7.4–12.0**	?	6.4–9.2	5.5–7.5
Length of lateral nasal ridge	33.8	33.7	35.6	29.0	32.7	damaged	?	32.8–34.0**	?	25.6–30.0	23.0–27.9
Length of suborbital ridge	98.7	98.0	96.6	98.2	100.0	97.3	?	91.0–95.1**	?	89.9–97.1	92.9–100.0
Snout width	24.7	23.0	22.9	24.0	26.9	28.4	?	26.2–29.0**	?	23.2–30.0 (decrease with growth)	20.0–27.4 (33.24)
Internasal width	17.6	16.9	17.8	18.9	20.2	damaged	22.7	16.4–19.0	12.6–13.0	15.2–20.0	15.9–18.1 (21.5)

......Continued on the next page