One embodiment provides a bone fastener including a collar, a fastener member, and a pin. The collar can have an upper portion with slot to receive an elongated member and a lower portion with a socket and an opening. The fastener member can have head and shank portions. The socket can receive the head portion and prevent movement of the head portion through the opening when the head portion is out of registration with the opening. The head portion and the socket can be configured to allow angulation of the fastener member within a defined range of motion within a selected plane. The head portion and the socket can define apertures which can be aligned with each other when the head portion is in the socket and which can receive the pin. One embodiment provides a generally spherical head portion with a flat.
