Diagnosis. Head with lateral lobes strongly produced, subocular margin strongly recessed. Mandible palp article 3 spatulate, shorter than article 2. Antenna 1 peduncle article 3 longer than article 1; accessory flagellum very small but distinct. Coxa 2 the largest, especially in male; coxae 3–7 relatively shallow. Gnathopods subchelate; male gnathopod 2 greatly enlarged. Uropod 3 rami longer than peduncle. Telson broad with a strong robust seta on each lateral crest.
Remarks. Megamphopus can be distinguished from all other genera within the Gammaropsis –group of genera, by its differentially enlarged male gnathopod 2 coxa.