No snake, modern or fossil, is known to have any vestige of arms or pectoral girdles. Vestigial pelvic girdles exist in the families Typhlopidae, Leptotyphlopidae, Aniliidae, Boidae, and the subfamily Cylindrophinae of family Uropeltidae (Mattison, 1995). Males may use these for intermale combat (Greene, 1997). Some primitive snakes have nerves in pelvic region suggesting their ancestors had legs (Mattison, 1995). Boas and pythons retain a cylinder a bone in their spurs and remnants of limb muscles (Ernst, 1996). Modern boas and pythons still retain small skeletal remnants of their hind limbs (pythons still possess an ilium, ischium, pubis, and short femur). These spurs are visible in the upper center of the following photos of the cloacal region of a boa (not to be confused with the hemipenes at the lower left of the photographs).