An anatomical investigation of the muscles of the pelvic outlet in Japanese giant salamander (Cryptobranchidae Megalobatrachus japonicus) with special reference to their nerve supply.

Four pelvic halves from two Japanese giant salamanders (Cryptobranchidae Megalobatrachus japonicus, one male and one female) were dissected in order to obtain detailed morphological data on the lumbosacral plexus and the muscles of the pelvic outlet. According to the positions of the passage of the metazonal nerves, the nerves can be divided into three groups: 1) the nerves passing dorsal to the caudofemoralis muscle, 2) the nerves passing between the caudofemoralis and the caudoischiadicus, 3) the nerves passing ventral to the caudoischiadicus. In consideration of the sites of origin from the lumbosacral plexus, a three-way stratificational analysis can be made, group 1 arising craniodorsal to group 2, and group 3 caudoventral to group 2. It is suggested that the three pelvic outlet muscles, the caudofemoralis, caudocruralis, and caudoischiadicus, have derived from the ventral muscles of the posterior limb, and have extended ventrocaudalwards.