Description
The cleftbelly trevally has a body shape similar in many ways to a number of the larger jacks, with a strongly compressed body almost ovate in shape. The dorsal profile of the head is straight and steep from the tip of the upper jaw to above the eye where the profile becomes convex. The eye lacks an adipose eyelid, and the upper jaw has a narrow band of small teeth, while the lower jaw has two or three rows of small teeth which narrow to one row on the sides of the jaw. The ventral profile is concave upwards, with a major distinguishing feature of the species being a deep median groove along the belly, into which the large pelvic fins fold, also encompassing the first two anal fin spines and anus. The entire chest from underneath the pectoral fins to the base of the pelvic fins is scaleless. There are two separate dorsal fins, the first with eight spines and the second with a single spine followed by 19 to 22 soft rays. The anal fin has two detached spines before the major part of the anal fin, which consists of one spine and 17 or 18 soft rays. The pectoral and pelvic fins are both quite long, with the latter extending almost to the anal fin origin. The lateral line has a moderately strong arch anteriorally which intersects the straight section underneath the fifth to seventh dorsal rays. The straight part of the lateral line has 31-37 scutes.
There are 24 vertebrae and 29 to 34 total gill rakers. The species is known to reach 26.5 cm in length, although often encountered below 20 cm.
The cleftbelly trevally is a bluish green on the upper body which fades to silver on the underside of the fish. The membranes of the large pelvic fin are a distinctive black, while the remaining fins are a pale white colour. Juveniles have indistinct dark bands across their bodies, with a black spot becoming more prominent in adults.
The species show sexual dimorphism in their dorsal fins, with mature males having between 6 and 12 elongated soft rays, strung out into filaments of varying lengths. The anal fin is also has five similar extensions of the soft rays. Females do not show this elongation.
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