Equulites leuciscus ( Günther 1860 ), Gunther, 1860

Chakrabarty, Prosanta, Chu, Jeanette, Nahar, Luthfun & Sparks, John S., 2010, Geometric morphometrics uncovers a new species of ponyfish (Teleostei: Leiognathidae: Equulites), with comments on the taxonomic status of Equula berbis Valenciennes, Zootaxa 2427, pp. 15-24 : 17-18

Equulites leuciscus ( Günther 1860)

Figures 1 and 2 b (Group B), Table 1 .

Equula leuciscus Gunther, 1860:503 ( Ambon Island, Moluccas Islands, Indonesia). Photoplagios leuciscus ( Gunther, 1860) : Sparks et al., 2005; Sparks and Chakrabarty, 2007; Chakrabarty and Sparks, 2008

Diagnosis. Equulites leuciscus can be distinguished from all other leiognathids by the following combination of features: a rhomboid shaped body (> 38% BD); a dorsal flank pattern of dark, thin to broad semicircular and oval shapes, a markedly elongate 2nd dorsal fin spine, a translucent triangular lateral flank patch in males that does not reach the pectoral-fin base or comprise a continuous or broken midlateral stripe. Equulites leuciscus can be further distinguished from E. elongatus and E. rivulatus by possessing a much deeper body (38-47% vs. 12.5-29.7% of SL) and from E. laterofenestra and E. klunzingeri by a translucent flank patch in males that does not reach the pectoral fin axil. The triangular lateral flank patch of males in E. leuciscus easily distinguishes it from E. antongil , E. stercorarius , and E. moretoniensis , all of which have a continuous or broken midlateral stripe.

Description. Equulites leuciscus is a medium-sized, elongate, and rhomboid-shaped ponyfish. The dorsal and ventral profiles are equally convex. The lower jaw profile is straight. The dorsal head profile is straight from the area dorsal to the orbit to the dorsal-fin origin. The lips are thin and not fleshy. The posterior margin of the maxilla is exposed and reaches a vertical through the anterior part of the orbit. The teeth are small and conical. The head is asquamate, whereas the remainder of the body (including the nuchal region) is scaled. In males, an expansive triangular, translucent patch, forming more or less an equilateral triangle, is present on the midflank. The base of the triangle is located parallel and slightly ventral to the midline of the body, and the vertex is located slightly dorsal to the anal-fin origin. The entire body is silvery, due to heavy guanine deposition. Pigmentation pattern on the dorsal flank comprises dark, thin to broad semicircular and oval shapes. There are 10 precaudal and 13 caudal vertebrae (including the ural centrum). There are eight dorsalfins spines and 16 rays in all individuals. There are three anal-fin spines and 14 rays in all individuals. The 2nd dorsal-fin spine is markedly longer than the remaining spines. The 2nd dorsal-fin spine may be up to twice the length of the 3rd spine and equal to or greater than the body depth, although these spines are broken in many individuals.

Figures

FIGURE 2. Specimens of Group A morphotype (A—Western Indian Ocean) and Group B morphotype (B—Eastern Indian Ocean)