Engyprosopon praeteritus ( Whitley, 1950 )

Amaoka, Kunio & Last, Peter R., 2014, The Australian Sinistral Flounder Arnoglossus aspilos praeteritus (Actinopterygii: Pleuronectiformes: Bothidae) Reassigned as a Valid Species of Engyprosopon, Species Diversity 19, pp. 91-96 : 91-94

Engyprosopon praeteritus ( Whitley, 1950)

( Figs 1 , 2A, C, D , 3–5 , 6A, B ; Table 1)

Arnoglossus aspilos praeteritus Whitley, 1950: 32 , fig. 1 (original description); Munro 1957: 16, fig. 463 (short description, figure from original description); Larson and Williams 1997: 373 (list); Hensley and Amaoka 2001: 3825 (note).

Arnoglossus aspilos (not of Bleeker, 1851): Hoese and Bray 2006: 1812 (note); Eschmeyer 2014 (note).

Material examined. Holotype: AMS IA. 4142, male, 57 mm SL, southwest of Cape Jaubert (19°S, 121°E), Western Australia, 5 m depth offshore, dredge, September 1929 . Paratypes: AMS IA. 4141, 53.1 mm SL, sex unknown, same station as holotype; AMS IA. 4284, 43.1 mm SL, sex unknown, Darwin, Emery Point (12.45°S, 130.30°E) and AMS IA. 4293, 42.1 mm SL, sex unknown, Port Darwin (12.45°S, 130.30°E), Northern Territory . Other specimens examined: CSIRO A 1261 , 88.2 mm SL, male, off Cape Peron, Shark Bay (25.30°S, 113.30°E), Western Australia , depth 11m, 27 August 1953; CSIRO A 1332–1337 , 69.0– 73.2 mm SL, 4 males and 2 females, Exmouth Gulf between Y-Island and Whale Beach (21.57°S, 114.25°E), Western Australia, 5 September 1953; CSIRO A 1338–1339 , 60.0– 60.5 mm SL, 1 male and 1 female, Exmouth Gulf (22°S, 114°E), Western Australia, 20 August 2003 . Fresh image examined: WAM P . 32685-001, 64.7 mm SL, sex unknown, Exmouth Gulf , Y- Island (54.85°S, 28.44°E), depth 7–9 m, otter trawl, 7 May 2004, collected by Sue Morrison .

Comparative materials. Arnoglossus aspilos: HUMZ 185345, 185346, 185347, 185350, and 185352, 80.0– 96.5 mm SL, 3 males and 2 females, Miyazu Bay, Kyoto Prefecture, 15–16 m, 17 October 2001.

Diagnosis. A species of Engyprosopon with a narrowly concave interorbital space; no obvious sexual dimorphism; prominent snout; tip of palatine bone distinctly protruding into mouth; 3–6 non-serrate gill rakers on upper limb; caudal fin with pair of small, black submarginal blotches; dorsal and anal fins each with series of black spots.

Description. Counts and morphometric data (given as proportions of SL and head length) as in Table 1.

Percent of SL: head length 24.4–27.5 (26.7 in holotype, 25.8-27.3 in paratypes); body depth 45.6–54.4 (49.1, 46.1– 47.1); snout length 5.6–7.0 (7.0, 5.9–7.0), upper eye diameter 5.4–7.4 (7.0, 6.6–7.4), lower eye diameter 5.6–7.1 (6.8, 6.0–7.1), interorbital width 1.2–3.8 (2.6, 1.2–1.9), length of ocular-side upper jaw 7.7–9.3 (8.8, 7.9–9.3), length of blindside upper jaw 6.8–8.4 (7.2, 6.8–8.4), length of ocular-side lower jaw 10.9–12.4 (11.9, 11.3–12.8), length of blind-side lower jaw 10.1–12.1 (11.2, 10.5–12.1), caudal peduncle depth 9.7–12.3 (13.0, 10.7–11.6), length of ocular-side pectoral fin 15.1–19.0 (16.1, 15.8–19.0), length of blind-side pectoral fin 10.9–13.0 (11.8, 11.2–13.0), length of ocularside pelvic fin 8.8–12.5 (11.4, 9.4–11.4), length of blind-side pelvic fin 8.5–11.4 (9.5, 9.2–11.4), length of base of ocularside pelvic fin 7.1–9.4 (8.8, 7.7–9.4), length of base of blindside pelvic fin 2.7–4.9 (3.3, 3.8–4.9), length of longest dorsal fin ray 11.5–14.0 (13.2, 11.3–14.0), length of longest anal fin ray 11.3–13.9 (12.5, 11.3–13.9).

Body ovate, deepest at middle of body, its depth nearly half of body length. Caudal peduncle rather shallow, its depth about equal to or slightly less than 1/4 of body depth. Head small, its length about 1/4 of SL; dorsal profile with deep concavity anterior to interorbital region. Snout rather long, prominent, length about equal to eye diameter; no rostral spine in either sex. Eyes small, about 70–80% of length of upper jaw, lower eye in advance of upper eye; no orbital spine in either sex. Interorbital region relatively broad, deeply concave, with no distinct ontogenetic or sexually dimorphic difference in its width ( Figs 2A, 2C, 2D , 3 ).

Mouth rather large, oblique; maxilla extending slightly beyond vertical drawn through anterior margin of lower eye; anterior tip of lower jaw slightly projecting beyond tip of upper jaw when mouth closed. No symphysial knob on ventral tip of mandible. Dentition of each side on upper jaw distinctly asymmetrical in shape and size; teeth on upper jaw conical and uniserial, more or less enlarged anteriorly; teeth on lower jaw similar to anterior teeth of upper jaw in size and spacing. Tip of vomer projecting far into mouth cavity. Gill rakers on first arch slender, not serrate, those on upper limb smaller than those on lower limb ( Fig. 5B ). Scales on ocular side moderate in size, deciduous, feebly ctenoid with very short ctenii ( Fig. 5A ); tips of both jaws and snout naked on ocular side; scales cycloid on blind side.

Dorsal fin highest at point slightly posterior to middle of body, its height about half of head length. Anal fin similar to dorsal fin in shape. Pectoral fin on ocular side short and feeble; that on blind side even more so, its length about 70– 80% of that on ocular side. Pelvic fin origin at tip of isthmus, fourth ray of ocular side opposite to first ray of blind side. Tip of isthmus at point nearly below posterior margin of lower eye. Caudal fin rounded posteriorly, three (rarely two) uppermost and lowermost rays branched.

Coloration when fresh (based on WAM P. 32685- 001). Body pale brownish on ocular side, without distinct blotches or spots; margins of scale pockets highlighted, darker brown. Caudal fin with two distinct dark blotches close to middle of fourth rays from upper- and lowermost margins of fin; dorsal and anal fins with series of finer dark spots; pelvic fin on ocular side with small black spot; orbital membrane speckled; entire ocular side becoming uniformly yellowish brown in preservative. Blind side of body pale yellowish white in both sexes in preservative.

Sexual dimorphism. This species does not display sexual dimorphism in either external morphology or coloration.

Distribution. Australian seas from Shark Bay (Western Australia) to Darwin (Northern Territory) ( Fig. 1 ).

Figures

Fig. 1. Collection localities of type series and present specimens of Engyprosopon praeteritus. H, holotype; P, paratypes. Numerals refers to number of specimens.

Fig. 2. Engyprosopon praeteritus (A, holotype, AMS IA. 4142, male, 57mm SL; C, CSIRO A 1336, male, 69.0mm SL; and D, CSIRO A 1335, female, 72.9mm SL) and Arnoglossus aspilos (B, HUMZ 185345, male, 87.1mm SL).

Fig. 3. Fresh image of Engyprosopon praeteritus. WAM P.32685-001, 64.7mm SL.

Fig. 4. Relationships between body depth in SL and SL (A) and between interorbital width in head length and SL (B). Engyprosopon praeteritus: holotype (△), paratypes(▲) and present specimens (■); Arnoglossus aspilos (●).

Fig. 5. Lateral line scale on ocular side (A), CSIRO A 1334,73.2mm SL and first gill arch (B), CSIRO A 1332, 73.1mm SL of Engyprosopon praeteritus.

Fig. 6. Radiographs of caudal skeletons of Engyprosopon praeteritus (A, holotype, AMS IA. 4142, male, 57mm SL; B, CSIRO A 1336, 69.0mm SL) and Arnoglossus aspilos (C, HUMZ 185346, 96.5mm SL). The hypural bones are split in A and B, and fused in C.