A surgical tool assembly, comprising: a surgical end effector movably coupled to a shaft assembly by an articulation joint that is configured to facilitate selective articulation of said surgical end effector relative to said shaft assembly about an articulation axis that is transverse to a shaft axis that is defined by said shaft assembly, said shaft assembly comprising: a proximal end; a distal end operably coupled to said articulation joint; a spine assembly comprising a distal spine end operably coupled to said articulation joint; a proximal closure member supported on said spine assembly for selective axial travel relative thereto, wherein said proximal closure member comprises an elongate proximal end portion and an elongate distal end portion; and characterised by an elongate notch in said shaft assembly on one lateral side of said shaft axis and located adjacent to said distal end, so as to facilitate more clearance between the shaft assembly and a pelvic structure of a patient, wherein said elongate notch further comprises; an elongate spine notch in said distal spine end on said one lateral side of said shaft axis; and an elongate closure member notch in said proximal closure member on said one lateral side of said shaft axis and corresponding with said elongate spine notch, wherein said elongate closure member notch comprises an asymmetric cut out in the elongate distal end portion of the proximal closure member. a surgical end effector movably coupled to a shaft assembly by an articulation joint that is configured to facilitate selective articulation of said surgical end effector relative to said shaft assembly about an articulation axis that is transverse to a shaft axis that is defined by said shaft assembly, said shaft assembly comprising: a proximal end; a distal end operably coupled to said articulation joint; a spine assembly comprising a distal spine end operably coupled to said articulation joint; a proximal closure member supported on said spine assembly for selective axial travel relative thereto, wherein said proximal closure member comprises an elongate proximal end portion and an elongate distal end portion; and characterised by an elongate notch in said shaft assembly on one lateral side of said shaft axis and located adjacent to said distal end, so as to facilitate more clearance between the shaft assembly and a pelvic structure of a patient, wherein said elongate notch further comprises; an elongate spine notch in said distal spine end on said one lateral side of said shaft axis; and an elongate closure member notch in said proximal closure member on said one lateral side of said shaft axis and corresponding with said elongate spine notch, wherein said elongate closure member notch comprises an asymmetric cut out in the elongate distal end portion of the proximal closure member. a proximal end; a distal end operably coupled to said articulation joint; a spine assembly comprising a distal spine end operably coupled to said articulation joint; a proximal closure member supported on said spine assembly for selective axial travel relative thereto, wherein said proximal closure member comprises an elongate proximal end portion and an elongate distal end portion; and characterised by an elongate notch in said shaft assembly on one lateral side of said shaft axis and located adjacent to said distal end, so as to facilitate more clearance between the shaft assembly and a pelvic structure of a patient, wherein said elongate notch further comprises; an elongate spine notch in said distal spine end on said one lateral side of said shaft axis; and an elongate closure member notch in said proximal closure member on said one lateral side of said shaft axis and corresponding with said elongate spine notch, wherein said elongate closure member notch comprises an asymmetric cut out in the elongate distal end portion of the proximal closure member. an elongate spine notch in said distal spine end on said one lateral side of said shaft axis; and an elongate closure member notch in said proximal closure member on said one lateral side of said shaft axis and corresponding with said elongate spine notch, wherein said elongate closure member notch comprises an asymmetric cut out in the elongate distal end portion of the proximal closure member.