Green-backed Croaker

Johnius amblycaphalus has its dorsal fin supported by a total of 11 spines and between 23 and 26 soft rays while the anal fin is supported by 2 spines and 7 soft rays. The second to the fifth spines in the first dorsal fin are elongated. The rear edge of the caudal fin can be truncate, rhomboidal or s-shaped. The chin has a single thick, blunt barbel. The overall colour is black or dark brown on the back and whitish or pale yellow on the sides and belly. The spiny dorsal fin is black towards its margin. This species has a maximum published total length of 25 cm (9.8 in) , although 15 cm (5.9 in) is more typical.

Johnius amblycephalus is found in the Indo-Pacific region where it occurs from the Persian Gulf to Papua New Guinea, north to southern China and Taiwan and south to Australia. Its presence off Africa is unconfirmed and may be confusion with Johnius fuscolineatus. It is found at depths between 0 and 28 m (0 and 92 ft) in shallow coastal waters and estuaries where there are sand, mud or muddy sand substrates as well as among soft corals, sponges, antipathrians, and algae.

Johnius amblycephalus has a specific name, amblycephalus, which means "blunt head" and this is an allusion to its relatively blunt snout in comparison to Johnius dussumieri.