An assembly comprising an airfoil for a turbine engine rotor wheel and a platform on which the airfoil is suitable for being mounted: · a plurality of said airfoils being suitable for being fastened to said platform or to a plurality of said platforms assembled together so as to form a rotor wheel having a wheel axis and defining upstream and downstream directions along that axis, the airfoils being arranged radially in the wheel; · in said wheel, the platform or the assembled-together platforms present a surface between the airfoils that is referred to as a platform surface and that radially defines the inside of gas-passing passages formed between the airfoils; and · said platform surface presenting a circumferential depression extending axially substantially between a leading edge and a trailing edge of an airfoil, a deepest section of said depression being situated axially in the upstream half of the airfoil; said assembly being characterized in that: where a "skeleton curve" (46, 47) is the curve representing the variations of a skeleton angle (α) of the airfoil in a section plane substantially parallel to the platform surface, as a function of position along the axis of the wheel; where a "linearized skeleton curve" is the curve representing variations of an angle as a function of position along the axis of the wheel, which curve is a straight line connecting together points representing the skeleton angle respectively at 10% and at 90% of the axial extent of the airfoil from the leading edge, in a vicinity of the platform, the skeleton curve presents a raised portion lying above the linearized skeleton curve. · a plurality of said airfoils being suitable for being fastened to said platform or to a plurality of said platforms assembled together so as to form a rotor wheel having a wheel axis and defining upstream and downstream directions along that axis, the airfoils being arranged radially in the wheel; · in said wheel, the platform or the assembled-together platforms present a surface between the airfoils that is referred to as a platform surface and that radially defines the inside of gas-passing passages formed between the airfoils; and · said platform surface presenting a circumferential depression extending axially substantially between a leading edge and a trailing edge of an airfoil, a deepest section of said depression being situated axially in the upstream half of the airfoil; said assembly being characterized in that: where a "skeleton curve" (46, 47) is the curve representing the variations of a skeleton angle (α) of the airfoil in a section plane substantially parallel to the platform surface, as a function of position along the axis of the wheel; where a "linearized skeleton curve" is the curve representing variations of an angle as a function of position along the axis of the wheel, which curve is a straight line connecting together points representing the skeleton angle respectively at 10% and at 90% of the axial extent of the airfoil from the leading edge, in a vicinity of the platform, the skeleton curve presents a raised portion lying above the linearized skeleton curve. where a "skeleton curve" (46, 47) is the curve representing the variations of a skeleton angle (α) of the airfoil in a section plane substantially parallel to the platform surface, as a function of position along the axis of the wheel; where a "linearized skeleton curve" is the curve representing variations of an angle as a function of position along the axis of the wheel, which curve is a straight line connecting together points representing the skeleton angle respectively at 10% and at 90% of the axial extent of the airfoil from the leading edge, in a vicinity of the platform, the skeleton curve presents a raised portion lying above the linearized skeleton curve.