All of the following from the boundary of MacEwen's triangle except
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
Temporal line
Posterosuperior segment of bony external auditory canal
Promontory
Tangent drawn to the external auditory meatus
Ear