The rostrum is relatively short compared to all other species in the genus, except, M. hectori and M. peruvianus. The melon forms a small bulge. The mouthline is straight.

Adult males are dark gray dorsally and grade to white ventrally. The ventral side of the tail flukes are pale gray with converging striations. There is a white patch around the umbilical scar. White linear scars are present on adult males, but appear to have been made by single tooth. Coloration of adult females has not been described.

Adult body length range is unknown. Recorded maximum body length for adult males and females is 3.9 m and 4.4 m, respectively. Length at birth is 2.1 m.