Current theses of the development of bladder exstrophy and its variants rely on defective evolution of the urinary tract and cloacal membrane. They do not account satisfactorily for the clinical features reported in children affected by exstrophy, especially the pelvic bone anomaly. We herein describe the normal development of the pelvic ring in the rabbit embryo and its chronological relationship with the lower urinary tract organogenesis. Our results suggest that these events are intricated and allow us to propose a novel mechanism to explain exstrophies.