Xenisthmus semicinctus, Gill & Hoese, 2004

Gill, A. C. & Hoese, D. F., 2004, Three New Australian Species of the Fish Genus Xenisthmus (Gobioidei: Xenisthmidae), Records of the Australian Museum 56, pp. 241-246 : 245-246

Xenisthmus semicinctus n.sp.

Fig. 3

Xenisthmus sp. 1 .—Allen & Russell, 1986: 100 (Rowley Shoals).

Type material. HOLOTYPE: WAM P.28025-048, 19.4 mm, male, Timor Sea , Rowley Shoals , Clerke Reef, lagoon, 1.5 km south of Bedwell Island, 17°18'S 119°22'E, 1–2 m, rotenone, G. R. Allen & R. C. Steene, 6 August 1983 . PARATYPE: WAM P.28025-068, 18.0 mm, presumptive male, collected with holotype .

Diagnosis. A species of Xenisthmus with the following combination of characters: second dorsal-fin rays I,12; analfin rays I,11; vertebrae 10 + 17; tongue indented; posterior naris with well-developed flap on anterior rim; upper sides of body with 12 large, closely spaced spots, each connecting dorsally to, or almost to, mid-line by short, brown to dark brown bar; and predorsal area broadly scaled to just behind vertical through posterior edge of preopercle, with narrow median wedge of scales extending further forward almost to pore D.

Description. Dorsal-fin rays VI + I,12, all segmented rays branched; first dorsal-fin pterygiophore formula 3–22110; anal-fin rays I,11, all segmented rays branched; pectoralfin rays 16/16 (15 f2), upper 1/1 and lower 1/1 (0 f2) rays unbranched; pelvic-fin rays I,5, inner ray unbranched; segmented caudal-fin rays 9 + 8; branched caudal-fin rays 8 + 7; upper unsegmented caudal-fin rays 7; lower unsegmented caudal-fin rays 7 (6); total caudal-fin rays 31 (30); scales in lateral series 55/60 (58 f2); scales in forward transverse series 19/21 (19 f1; 20 f1); scales in backward transverse series 19/21 (17 f1; 19 f1); circumpeduncular scales 28 (27); predorsal scales 21 (20); cheek scales 4; gill-rakers 3 + 10 (2 + 9); pseudobranch filaments 3; vertebrae 10 + 17; epurals 2.

As thousandths of SL: head length 242 (244); predorsal length 324 (339); prepelvic length 237 (233); preanal length 485 (533); first dorsal-fin origin to second dorsal-fin origin 180 (189); second dorsal-fin base length 335 (322); analfin base length 294 (289); pectoral-fin base depth 72 (67); first dorsal-fin origin to pelvic-fin origin 160 (172); second dorsal-fin origin to anal-fin origin 144 (150); snout length 41 (38); orbit diameter 62 (61); head width 160 (133); body width 113 (111); bony interorbital width 15 (11); snout tip to retroarticular tip 113 (111); caudal-peduncle length 175 (183); caudal-peduncle depth 113 (111); length of first spine of first dorsal fin 67 (83); length of third spine of first dorsal fin 82 (83); length of sixth spine of first dorsal fin 57 (67); length of spine of second dorsal fin 77 (83); length of first segmented ray of second dorsal fin 98 (94); length of last segmented ray of second dorsal fin 113 (111); anal-fin spine length 62 (67); length of first segmented anal-fin ray 88 (89); length of last segmented anal-fin ray 129 (106); pectoral-fin length 206 (211); fourth segmented pelvic-fin ray length 175 (178); caudal-fin length 201 (211).

Body covered with small scales; scales cycloid on anterior body, ctenoid on mid-side (behind vertical through middle of anal-fin base) and caudal peduncle; ventral contour of body fully scaled, except for narrow area beneath branchiostegal membranes; predorsal broadly scaled to just behind vertical through posterior edge of preopercle, with narrow median wedge of scales extending further forward almost to pore D; cheeks and upper part of operculum scaled; scales present on pectoral-fin base; narrow band of mostly ctenoid scales on fleshy portion of caudal-fin base; no scales on dorsal- or anal-fin bases.

Head pores A'BC D(S)EFHIJK' M'NOPQ'; lower lip fleshy and protruding, with uninterrupted, free ventral margin; anterior naris in short tube; posterior naris with raised rim, with prominent membranous flap anteriorly; tongue indented anteriorly; gill opening extending anteriorly to about midway between verticals through posterior edge of preopercle and posterior edge of eye.

Upper jaw with 3 (anteriorly) or 2 (posteriorly) rows of small, conical teeth, outer-row teeth larger and slightly curved; lower jaw with 3 (anteriorly) or 2 (posteriorly) rows of small, conical teeth, outer-row teeth larger and slightly curved; vomer, palatines and tongue edentate.

Preserved coloration. Head and body beige to pale brown; short, narrow, dark grey-brown stripe extending from midanterior orbital rim to mid-side of upper lip; second dark grey-brown stripe extending from mid-posterior orbital rim to shoulder, overlapping upper part of pectoral-fin base; median spot or short bar on upper nape, just anterior to vertical through pectoral-fin base; sides of body with 12 large, dark brown spots, each connecting dorsally to, or almost to, mid-line by short, brown to dark brown bar; first bar and spot just behind pectoral-fin base, second at first dorsal-fin origin, third through middle of first dorsal-fin base, fourth between dorsal fins, next six equally spaced along second dorsal-fin base, final two on caudal peduncle; dorsal fins hyaline with narrow, dark grey-brown stripe along distal third of fins, and series of dark grey-brown spots at base of fins (aligning with bars on body); caudal fin hyaline with short, dark grey to grey-brown bar or spot between third lowest ray on upper hypural plate and upper ray on lower hypural plate, just posterior to their basal tips; bar or spot edged anteriorly with brown to dark brown; remainder of caudal fin with three or four narrow, wavy bars, best developed on upper part of fin; anal fin hyaline with narrow dark grey-brown stripe along distal third of fin; pectoral and pelvic fins hyaline to beige.

Live coloration. Not known.