Opistognathus alleni, Smith-Vaniz, 2004

Smith-Vaniz, William F., 2004, Descriptions of Six New Species of Jawfishes (Opistognathidae: Opistognathus) from Australia, Records of the Australian Museum 56 (2), pp. 209-224 : 210-212

Opistognathus alleni n.sp.

Figs. 1, 2A, 3A, 4A; Tables 1–4

Opistognathus sp. —Allen & Swainston, 1988:126, pl. 54, colour fig. 814 (brief diagnosis; common name “Abrolhos jawfish”).

Type material. HOLOTYPE: WAM P.27590-030, male (73.7), Western Australia, Houtman Abrolhos Archipelago, N. end of Dicks Island, in Goss Passage , 28°30'S 113°46'E, 30–32 m, G. R. Allen and N. Sinclair, 17 Apr. 1982 . PARATYPES: 39 specimens, 45.4–72.4 mm, all from Western Australia. WAM P.27590-002 (11, 47.4–72.4), same data as holotype; WAM P.27587-003 (54.0), Houtman Abrolhos Archipelago, S. end Long Island, in Goss Passage , 28°29'S 113°46'E, 25–32 m, G. R . Allen, 16 Apr. 1982; AMS I.33668-001 (3, 51.4–66.1), ANSP 157594 (4, 53.8–66.2,

1 C&S), NTM S.13294-001 (3, 50.5–55.1), USNM 315663 (3, 62.7–68.7) and WAM P.27595-003 (9, 45.4–51.2), Houtman Abrolhos Archipelago, all from Long Island , in Goss Passage, 30–33 m, G . R. Allen et al., 19 Apr. 1982 . MPM 33192 (53.7), Exmouth Gulf, Burnside Island , 22°5'33"S 114°30'55"E, 0–0.6 m , R.D. Mooi , A.C. Gill, J.B. Hutchins and R.C. Miles, 19 May 1996 . BMNH 2001.11 .28.1 (45.3) and MPM 33191 (2, 40.6–46.8), Locker Island , 21°42'12"S 114°45'48"E, 0–0.2 m , R.D. Mooi , A.C. Gill and R.C. Miles, 16 May 1996 . MPM 33190 (45.9), Bessieres Island , 21°31'2"S 114°45'13"E, 13–15 m , R.D. Mooi , A.C. Gill , R. C. Miles and N. Williams, 15 May 1996 .

nape, area above lateral line, pectoral-fin base and breast; belly squamation varying from completely naked to posterior ¼ scaly. Body with about 21–31 oblique scale rows in longitudinal series. Lateral-line terminus below verticals from 13th to 17th segmented dorsal-fin rays (total element position 23–27). Lateral line pores numerous, arranged in multiple series above and below embedded lateral-line tubes. Cephalic sensory pores very numerous, in adults completely covering most of head, including all of predorsal area except a small area immediately adjacent Diagnosis. A species of Opistognathus with dorsal fin X, 19 (rarely 20); body with about 21–31 oblique scale rows in longitudinal series, and scales absent anterolaterally forward of verticals from 6th to 9th segmented dorsal-fin rays; spinous dorsal fin with a broad dark submarginal stripe and spine tips with pale fleshy tabs; vomerine teeth 1–3.

Description. Dorsal-fin rays X, 19 (rarely 20). Anal-fin rays II, 17–18 (typically 18). Pectoral-fin rays 19 or 20. Caudal fin: procurrent rays 4–5+3–5, segmented rays 8+8, middle 12–14 branched, total elements 23–26; hypural 5 present or (usually) absent. Vertebrae: 10+22 (10+ 23 in one of 35 specimens); last pleural rib on vertebra 10; epineural ribs 11–15. Supraneurals absent, insertion pattern 0/0/1/1+1/1/.

Gill rakers 8–10+16–18 = 24–28.

Scales absent on body anterolaterally forward of verticals from 6th to 9th segmented dorsal-fin rays, and from head, to dorsal-fin origin; mandibular pore positions 1–3 occupied by relatively large, single pores, 4th position with 6–12 pores, 5th position with 19–30.

Anterior nostril distinctly closer to posterior nostril than to dorsal margin of upper lip, and with a simple, flattened tentacle on posterior rim that when depressed reaches margin of orbit; height of tentacle about 1.5 to 2.0 times maximum diameter of posterior nostril. Dorsal fin very low anteriorly, gradually increasing in height posteriorly; profile relatively uniform with only a slight change in fin height at junction of last spine and anterior segmented rays. Dorsalfin spines relatively short and straight, at most only slightly curved distally and without flexible tips; skin covering tips of spines with slightly swollen fleshy tabs; all segmented dorsal- and anal-fin rays branched distally. Outermost segmented pelvic-fin ray not tightly bound to adjacent ray, interradial membrane incised distally. Upper margin of opercle straight and slightly rounded posterodorsally; posterior margin of preopercle indistinct, without a free margin. No papillae on inner surface of lips. Fifth cranial nerve passes under A1 section of adductor mandibulae.

Upper jaw not sexually dimorphic, extending 0.4 to 0.6 eye diameters behind posterior margin of orbit; maxilla widest at end and truncate, without flexible lamina posteriorly ( Fig. 2A); supramaxilla present, small and terminally positioned. Jaws subequal. Premaxilla with an outer row of moderate conical teeth that become progressively smaller and more closely spaced posteriorly and extend 2 3 length of jaw; 1 or 2 rows of smaller inner teeth anteriorly, and usually 2–3 inner teeth on each side of premaxillary symphysis that are somewhat enlarged and canted backwards. Dentary with outer row of conical teeth (slightly smaller than outer symphyseal premaxillary teeth) that are usually slightly larger midlaterally, and 3 or 4 inner rows of teeth (about same size as anterior, outer row teeth) anteriorly, those in innermost row canted backwards. Vomerine teeth 1–3. Infraorbital bones tubular with wide openings for sensory canals ( Fig. 3A); 3rd infraorbital relatively robust with a slight suborbital shelf. Second pharyngobranchial very slender and Y-shaped ( Fig. 4A).

Measurements of the 73.7 mm holotype (in parentheses) and 12 paratypes, 54.3–72.4 mm, as percentage of SL: predorsal length (31.2) 28.1–31.8; preanal length (53.4) 53.8–59.0; dorsal-fin base (71.2) 69.4–73.9; anal-fin base (40.2) 37.6–43.0; pelvic-fin length (18.0) 17.0–20.4; caudalfin length (19.5) 17.9–20.8; depth at anal-fin origin (14.2) 12.0–15.6; head length (31.3) 28.7–33.0; orbit diameter (9.2) 8.3–10.4; upper jaw length (15.0) 14.2–16.3. As percentage of head length: postorbital head length (64.9) 63.4– 68.4; upper jaw length (47.9) 46.8–52.0; postorbital jaw length (16.3) 13.5–17.4; orbit diameter (29.3) 29.0–32.8.

Preserved coloration. Head and body with scattered pale spots and mottled with various shades of brown; sides with dark midlateral stripe about width of eye and bordered above and below by a row of pale spots, some poorly defined, that contact margins of stripe giving it a scalloped outline; dorsum of some specimens with about 8–10 evenly spaced tan blotches superimposed with small dark spots that extend slightly below lateral line along dorsal-fin base and alternate with upper row of pale spots; pectoral-fin base with large white spot (not shown in illustrated specimen); posterodorsal margin of opercular flap with dark margin; in large specimens, dusky spots usually ring orbital rim, at least dorsally; upper lip with 1 or 2 dusky bands below or slightly behind posterior margin of eye; inner lining of maxilla and mouth pale or light brown but without a distinct blotch or stripe; spinous dorsal fin with a broad submarginal brown stripe and spine tips with noticeably pale fleshy tabs; soft dorsal fin with a narrow dark stripe near base of fin that is bordered above by several rows of small dark spots or blotches; anal fin mostly pale, usually with very narrow brown stripe on proximal third of fin; caudal fin with a pair of pale, oblong, basicaudal spots widely separated by a brown blotch that is a continuation of the midlateral stripe; otherwise caudal fin mostly pale with very faint dusky bands or spots that are best developed on dorsal half of fin; pelvic and pectoral fins immaculate. Some of the non-Houtman Abrolhos Archipelago paratypes (which appear to have better preserved colour patterns) have a conspicuous white cheek spot, positioned slightly below the mid-point of postorbital margin of eye that is bordered above by a small dark spot, and 1 or 2 white spots on the opercule.

Live coloration (based on photograph, taken by R.D. Mooi, of freshly collected 53.7 mm SL specimen from Burnside Is.): dark chocolate brown stripe in dorsal and anal fins and midlaterally on sides; background coloration of head and body light yellowish brown; pale spots on cheek, opercle, pectoralfin base and most of those below midlateral stripe on sides white, other pale spots light yellowish brown; iris pale yellow with a few narrow dark bands radiating from pupil. This individual also has small prominent white spots on the belly that are either absent or less defined in the other specimens.

Etymology. Named in honour of Dr Gerald R. Allen, who recognized the undescribed status of this species, generously made his material available for this study, and whose publications have contributed significantly to knowledge of Indo-Pacific fishes.

Distribution. Known only from Western Australia in depths of 0.2– 33 m.

Remarks. In O. alleni the second pharyngobranchial is very slender and essentially Y-shaped ( Fig. 4A), in most other species of Opistognathus this edentate bone is rod-like with the distal end slightly to moderately expanded (character not examined in O. stigmosus and O. elizabethensis ), and in O. seminudus the end is greatly expanded ( Fig. 4B).