Abstract

Gerres silaceus n. sp. is described from the holotype and two paratypes from the southern Malay Peninsula. The species is included as the fourth species in the “G. setifer complex” [G. chrysops Iwatsuki, Kimura and Yoshino, G. decacanthus (Bleeker), G. setifer (Hamilton), G. silaceus n. sp.], differing from all other congeners from the Indo-Pacific in having two supraneural bones and small size (less than 100 mm in standard length vs three supraneural bones and adults > 100 mm SL). The new species is further characterized by presence of IX, 10 dorsal fin rays, 34 or 35 lateral line scales, 3.5 scales between the 5th dorsal fin spine base and lateral line, caudal fin short (mean 29% of SL), slender second anal fin spine, pelvic fin ray with a wide white margin posteriorly, and a uniformly silvery ocher body. Gerres silaceus differs from G. setifer and G. decacanthus in body color, the last dorsal fin spine slightly shorter or similar length to the penultimate spine, higher gillraker counts and broadly rounded caudal fin lobes; it differs from G. chrysops in higher gillraker counts, rounded caudal fin lobe posterior margin and body color. The four species are generally distributed allopatically in the Indo-western Pacific.