Most parsimonious scenarios of the early karyotype evolution within the family Mormyridae including three variants (A–C) of karyotype structure in a hypothetic ancestor (HA) and three studied lineages (the genera Petrocephalus, Stomatorhinus and Mormyrops) with least advanced karyotype structure within the family. The alternative transformations of karyotype structure are joint with a dashed line. The solitary submetacentric pairs in Petrocephalus and Stomatorhinus are suggested to be not syntenic.