An anatomical investigation of the muscles of the pelvic outlet in iguanas (Iguanidae Iguana iguana) and varanus (Varanidae Varanus (dumerillii)) with special reference to their nerve supply.

Five pelvic halves from three male iguanas (Iguanidae Iguana iguana) and two pelvic halves from one male varanus (Varanidae Varanus (dumerillii)), were dissected in order to obtain detailed data on the relationship of 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 major, 3) the nerves passing ventral to the caudoischiadicus major. In consideration of the sites of origin from the lumbosacral plexus, a stratificational analysis can be proposed; group 1 arises craniodorsal to group 2, and group 3 caudoventral to group 2. It is suggested that the pelvic outlet muscles (caudofemoralis, quadratus caudae, obliquus cloacae, transversus cloacae profundus, retractor penis, caudoischiadicus major, and the caudoischiadicus minor) are derived from the ventral muscles of the posterior limb, and have moved caudally concomitant with the caudal migration of the cloaca.