Melon is moderately bulbous and merges smoothly with rostrum, such that there is little demarcation between the forehead and long, narrow beak. The posterior half of the jaw is prominently arched in males; in females this arch is less pronounced, but still has a noticeable sinusoidal curve.
In adult males, the rostrum and anterior portion of the mandible back to the posterior edge of the tooth are white. There is also a distinctive white patch of variable extent centered on the dorsal prominence of the melon. The rest of the body is relatively uniform dark grey to black, with no discernable differentiation between dorsal and ventral surfaces. Males often have extensive linear and ovate scars, especially on the flanks. The ventral surface of the body is lighter in females and juveniles, grading from medium gray dorsally to white on the midventral portions. The flipper pocket in females is darker than adjacent areas of thorax. Females and juveniles also have less contrast in the head coloration, but the rostrum and mandible are lighter than the rest of the head. Females appear to show greater variation in the pigmentation patterns around the rostrum.
Both sexes exhibit fluke coloration that is lighter on the ventral surface than the dorsal surface. Flukes are also marked on ventral surface with concentric striations radiating anteriorly from the position of the caudal vertebra.
Adult body length ranges between 4.8 to 5.3 m. Recorded maximum body length for both adult males and females is 5.3 m. Body length at birth is 2.5 m.
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