Like all members of the genus "Synodontis", "S. granulosus" has a strong, bony head capsule that extends back as far as the first spine of the dorsal fin. The head is about of the standard length of the fish. The head contains a distinct narrow, bony, external protrusion called a humeral process. The shape and size of the humeral process help to identify the species. In "S. granulosus", the humeral process is narrow, long, and rough in appearance, with a distinct ridge on the bottom edge. The top edge is concave and the end is sharply pointed. It is about of the length of the head. The diameter of the eye is about of the length of the head.