All fins well developed, length and position of dorsal and anal fin, respectively, often are distinctive characters of the genera. Body usually laterally compress, from deep to elongate. Coloration varies from uniform black or dark brown to pinkish or bluish and silvery with clear countershading, often dark bar(s) between dorsal and anal fin or white markings on trunk and tail, or dark marks on or below dorsal fin and/or on caudal fin.
This family consists of two subfamilies, together they include about 200 species.
Subfamily Mormyrinae , with 17 genera.
Subfamily Petrocephalinae , with one genus, Genus Petrocephalus