RESUMEN
The flexor digitorum superficialis (FDS) muscle is located in the intermediate layer of the muscles in the anterior compartment of the forearm. Variable but individual variations have been reported in the FDS regarding the number of head and the origin, distribution and interconnections of muscle slip and insertion to finger. In this case, we report a concomitant complex variation in FDS which was observed in a cadaver during a routine dissection classes for the undergraduate medical students. It includes the variation which is the separation of the tendon of FDS into the superficial and deep layers, the structural variations in muscle slips and associated tendon variations, the finding of Gantzer' muscle leading to flexor pollicis longus muscle. These complex variations in FDS are very rare case and this report summarizes the related phylogenetic and embryological significance.