Enneapterygius gracilis Fricke 1994
Creators: name: Dewa, Yuna
name: Tashiro, Satokuni
name: Motomura, Hiroyuki
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Perciformes
Tripterygiidae
Enneapterygius
Enneapterygius gracilis

description: Enneapterygius gracilis Fricke, 1994
[English name: Northern Yellow-black Triplefin]
Figures 4, 7; Tables 2, 6, 7
Enneapterygius gracilis Fricke, 1994: 209, fig. 34 (original description; type locality: Danger Point, Cobourg Peninsula, Northern Territory, Australia); Larson and Williams, 1997: 367 (Nightcliff, East Point, and Lee Point Reef, Northern Territory); Fricke, 1997: 567 (Western Australia, Northern Territory, and Queensland); Hutchins, 2001: 41 (Western Australia); Hoese, 2006: 1520 (Gulf of Carpentaria, Northern Territory); Larson et al., 2013: 177 (Northern Territory: Burford Island; Trepang Bay, Cobourg Peninsula; North Oxley Island; East Vernon island; Veronica Island, Gove Peninsula; Yirrkala Reef).
Holotype. NTM S. 10431-027, male, 19.7 mm SL, Danger Point, Cobourg Peninsula, Northern Territory, Australia, 11°08′S, 132°20′E, 0–1.5 m, 1 May 1982, B. Russell et al.
Paratypes. 8 specimens (15.8–20.7 mm SL). NTM S. 10431-034, female, 16.5 mm SL, same data as holotype; AMS I. 17060-043, 3 males and 3 females, 18.3–20.7 mm SL, Exmouth Gulf, Western Australia, 22°15′S, 114°15′E, 19 Jan. 1972, W. Ponder; AMS IB. 7075, female, 15.8 mm SL, Bountiful Island, Gulf of Carpentaria, Queensland, 16°41′S, 139°50′E, Dec. 1963, J. Yaldwyn.
Non-type specimen. AMS I. 25500-005, male, 19.5 mm SL, 5 km north of Learmouth, Exmouth Gulf, Western Australia, 22°20′S, 114°10′E, 10 Sept. 1985, D. Hoese & D. Rennis.
Means in parentheses
Diagnosis. A species of Enneapterygius (Fig. 7) with the following combination of characters: 11 or 12 (modally 12) second dorsal-fin spines; 9–11 (9) third dorsal-fin rays; I, 16–18 (7) anal-fin rays; ii–iv (iii) + 4–6 (5) + vi–vii (vii) = 14–16 (15) pectoral-fin rays (iii + 5 + vii = 15 in holotype and 4 paratypes, iv + 4 + vii = 15 in 2 paratypes, iv + 5 + vii = 16 and ii + 6 + vi = 14 in single paratype specimen and non-type specimen); 12 or 13 (13) pored lateral-line scales; 19–22 (21) notched lateral-line scales; 31–34 (32) scales rows in longitudinal series; 2 or 2½ (2) scales above 1st pored lateral-line scale; 3 or 3½ (3) scales below 1st notched lateral-line scale; 8 circumpeduncular scales; mandibular pores 3–4 + 1–2 + 3–4 (usually 3 + 2 + 3) (Fig. 8A) (3 + 2 + 3 in holotype, 6 paratypes, and a non-type specimen, 3 + 1 + 3 and 4 + 2 + 4 in single paratype only); head relatively long, its length 29.2–32.5% (mean 30.6%) of SL; upper jaw length 9.2–11.7% (11.0%) of SL; 1st spine of first dorsal fin slightly longer than that of 2nd dorsal fin, its length 10.8–17.9% (13.9%) of SL; anterior nostril tentacle unbranched; orbital tentacle circular, the edge slightly pointed, its length slightly less than or subequal to pupil diameter; body generally yellowish or brownish with 6 or 7 bands, darker around lateral line; brownish blotches on each pectoral-fin ray, forming 3 or 4 narrow bands; anal fin with 7–9 brownish oblique bands; caudal fin translucent with 5 vertical bars; body yellowish, lower half of head and pectoral-fin base black in nuptial males.
Distribution. Enneapterygius gracilis is distributed only in northern Australia, where it ranges from Western Australia (Exmouth Gulf) to the Northern Territory (East Point, Nightcliff, Lee Point, East Vernon Island, Burford Island, Trepang Bay, North Oxley Island, Veronica Island, Yirrkala Reef) and Queensland (Bountiful Island) (Fricke, 1994; Larson & Williams, 1997; Fricke, 1997; Hutchins, 2001; Hoese, 2006; Larson et al., 2013) (Fig. 4).
Remarks. Although Fricke (1994) described the symphyseal mandibular pore of E. gracilis as single (mandibular pore formula 3 + 1 + 3), examination of specimens, including the holotype, in this study revealed that E. gracilis has double symphyseal mandibular pores, the mandibular pore formula being revised as 3 + 2 + 3, accordingly. Enneapterygius gracilis is similar to E. olivaceus n. sp. in having a long head [29.2–32.5% (mean 30.6%) of SL], 1st spine of the first dorsal fin [10.8–17.9% (13.9%) of SL], and orbital tentacles (slightly less than or subequal to pupil diameter) (Figs 5, 6). However, the former differs from the latter in notched lateral-line scale and scales below the 1st notched scale numbers, and mandibular pore formula (Figs 5, 6) (see E. olivaceus n. sp. Remarks.)
description: Published as part of Dewa, Yuna, Tashiro, Satokuni & Motomura, Hiroyuki, 2023, A new species of the genus Enneapterygius (Perciformes: Tripterygiidae) from Japan and the Philippines, with a synopsis and synonymy of related species, pp. 333-360 in Zootaxa 5374 (3) on pages 342-344, DOI: 10.11646/zootaxa.5374.3.2, http://zenodo.org/record/10150204