Principal component analysis scatterplot of 10 Quadriacanthus specimens of each of the following species: Quadriacanthus euzeti from Papyrocranus afer, Quadriacanthus barombiensis n. sp. from Clarias maclareni, Quadriacanthus anaspidoglanii from Anaspidoglanis macrostoma and Quadriacanthus levequei from Clarias jaensis. A: axes 1 and 2, B: axes 1 and 3. C and D: scatterplot of variable along axis 1 and 2 and axis 1 and 3, respectively. Dorsal anchor: (DAa) length, (DAab) base width, (DAe) point length. Ventral anchor: (VAa) length, (VAab) base width, (VAe) point length. (Ap) Accessory piece length, (MCO) Male copulatory organ length. Cuneus: (Cj) length, (Ci) width. (DB) Dorsal bar: (DBct) center length, (DBh) median process length, (DBw) width, (DBx) length. Ventral bar: (VBw) width, (VBx) length. (I–VII) Hook length.