A case of lumbar split cord malformation (SCM) with a bony spur situated dorsally is presented. This was associated with a hypertrophied posterior arch. The ventral dura was totally intact, and there was no fibrous septum connecting the bony arch to the dura. To our knowledge, such a case has not been reported earlier. In view of this unique finding, we propose a slight modification in Pang's unified theory of embryogenesis in the development of SCM.