Eurypoda is a form derived from the thyreophora which contains stegosaurs and their sister group the ankylosaurs. They all share the characteristics which include short stocky metacarpal and metatarsal bones; reduction in the fourth trochanter; shortened postacetabular process of the ilium (the part of the ilium behind the hip socket); loss of a phalanxin digit IV of the foot; special bones that fuse to the margins of the eye socket; loss of a notch between the quadrate and the back of the skull; and an enlargement of the forward part of the ileum.