<prompt> All of the following from the boundary of MacEwens triangle exceptTemporal linePosterosuperior segment of bony external auditory canalPromontoryTangent drawn to the external auditory meatus  <response>: Bounded by Temporal line, the Posterosuperior segment of a bony external auditory canal, Tangent drawn to the external auditory meatus. Impoant landmark to locate mastoid antrum in mastoid surgery. Ref: Dhingra 6th edition 